Thursday, April 16, 2015

April 9th Tornadoes in Northern Illinois

This year's severe weather season got off to a slow start for much of the country. In fact, the first severe weather watches in March weren't issued until March 24, which was the latest first March watch in 45 years. In the three weeks following another 53 watches have been issued, a rate more typical of this time of year. Last year there were 1045 severe weather reports through April 15, and this year the count was at 923.

2015 severe weather reports (wind (blue), hail (green), and tornadoes (red)) through April 15.
One of the more spectacular, impressive, and certainly damaging events of the year to date occurred on April 9 in the Midwest.

By now you have probably seen some of the photos and video taken of the tornado in northern Illinois. Now that the dust has settled on this event it's a good time to look at some of the summaries and descriptions of the event that are available. It's not too unusual for there to be numerous videos and countless photographs of tornadoes these days, but this event caught my attention because it was, for lack of a better description, so photogenic and several people captured incredible images. Wide open spaces and clear views of storms are usually the calling card of the southern, central, and northern Plains, not northern Illinois.

Last Thursday's severe weather was anticipated and well-forecast by the NWS. The bulls-eye location for this severe weather event extended from eastern Iowa through northern Illinois, an area located southwest of an intensifying surface low. A warm, humid highly unstable air mass was in place over this area, strong winds aloft, converging winds at the surface, and a 30°F temperature difference from north to south of the warm front.

Annotated surface map for 6:00 p.m. April 9.
Source: National Weather Service Chicago

Most of Illinois and eastern Iowa was in an area of Enhanced Risk for severe weather in the 11:30 CDT convective outlook from the Storm Prediction Center.

The convective outlook issued at 11:30 a.m. CDT on April 9 showing and area of Enhanced Risk from Texas to Illinois and Indiana. On the left is a graphic showing the highest tornado probability from eastern Iowa across northern Illinois.


Storms began to develop during the late afternoon in eastern Iowa and northwestern Illinois. By 6:00 p.m. a strong thunderstorm was developing in northern Ogle County. At 6:09 p.m. the National Weather Service issued a tornado warning for this storm.

Radar image at 6:10 p.m.


At 6:29 p.m. a funnel cloud was reported south of the Rockford Airport, and eight minutes later a tornado was on the ground just south of Cherry Valley, IL. This was a short-lived EF0 tornado. The storm that produced the EF4 was was rapidly developing to the southwest of the first storm.


At 6:35 p.m. a tornado warning was issued on the big supercell. A tornado was reported on the ground near Franklin, IL, between Dixon and Rochell just north of Interstate 88.


Radar image at 6:35 p.m.showing warned storm that produced the Fairdale tornado.
The Fairdale tornado just after formation as it intensifies and strikes Crest Foods in Ashton, IL. Debris is clearly seen in the lower half of the funnel.  Photo by Walker Ashley, used with permission.

Over the next 40 minutes this tornado traveled 30 miles, destroying much of the village of Fairdale, IL and producing EF4 damage at several points along its path.this one thunderstorm eventually produced six tornadoes.

When the day was over there were a total of 11 tornadoes confirmed in Illinois, seven of those in northern Illinois, and one in Iowa. There were also three tornadoes reported in eastern Missouri and three in Texas that day.

The path of this tornado was through a lightly populated area of northern Illinois, well west of the Chicago metropolitan area. However, it passed just three miles north of Rochelle, a city of 9,500 people. Had the path of this tornado been located 13 miles to the northwest it would have plowed through the city of Rockford (pop. 150,250). If the track of this tornado were 15 miles to the southeast of the actual path the tornado would have passed through De Kalb (pop. 43,850), the home of Northern Illinois University, and Sycamore (pop. 17,500).

Here is a map of all severe reports received on April 9 superimposed on the outlook issued by the Storm Prediction Center at 11:30 CDT.



There are number of descriptions of the analysis and events of that day that are worth reading. The NWS Chicago office has an updated page, "April 9, 2015 Tornado Event, Including Rochelle/Fairdale EF-4 Tornado". At the bottom of that page are links to event descriptions from NWS Quad Cities, NWS Central Illinois, and NWS Paducah, KY where the other tornadoes occurred. The page has photos, detailed tornado  tracks, radar images, and an analysis of the weather of that day.

Walker Ashley, a professor of meteorology at Northern Illinois University, Certified Consulting Meteorologist,  and well-known storm chaser has written a blog post about his experiences that day chasing the Fairdale tornado, including remarkable photographs and videos he recorded.

The NWS Chicago has a Facebook photo album of storm photos submitted by the public of the storms that day. You do not need a Facebook account to view these.

Dennis Mersereau at The Vane also has a nice blog post with an in-depth look of the tornado.
.

Tuesday, April 7, 2015

Undertanding Severe Thunderstorm Risk Categories

In October the Storm Prediction Center implemented two additional severe storm risk categories in their outlooks. I blogged about these changes at the time (Changes to Severe Weather Outlooks), but now that we are in the heart of severe storm season I thought it would be a good idea to mention these changes again. You can read a lot more about the specifics in my October blog post. Recently the National Weather Service office in Kansas City (Pleasant Hill) and the Storm Prediction Center in produced a new graphic that should make understanding the differences between these categories easier. The SPC worked with NWS offices and forecasters, communications experts, social scientists, and the public to come up with the descriptions for the severe thunderstorm risk categories.

First, let's take a look at the Day 2 outlook (for Wednesday) issued earlier today, as it shows both the Marginal and Enhanced categories.

This is the SPC outlook for Wednesday, April 8 made on Tuesday, April 7. The Marginal Risk is in dark green, the Slight Risk in yellow, and the Enhanced Risk in Orange.

How should you interpret the risk for severe thunderstorms in each area? Here's the graphic produced by the NWS.
 

You can read more about the science and numbers behind the severe storm categories at the Storm Prediction Center web site.

One important thing to remember is that any thunderstorm, severe or not, is potentially dangerous. Lightning is the second leading cause of weather fatalities in the U.S., second only behind floods. Lightning itself is not a criteria for a severe thunderstorm. Don't be lulled into a false sense of security by a lower risk category.

You can read more about the science and numbers behind the severe storm risk categories at the Storm Prediction Center web site.

Also, on April 14 the SPC will add a new Summary section to Public Watch Notification Messages. Per the SPC, "The new Summary section is a general 1-2 sentence statement of the severe weather expected in and close to the watch area. This new section facilitates consistent, forecaster-driven, concise communication for public consumption. The Summary is intended to be useful for a variety of communication needs including web page headlines, social media and multimedia briefings."

Wednesday, April 1, 2015

Slow Start to Severe Weather Season

The first Severe Thunderstorm Watch of March 2015
The late but long winter segued into a very slow start to the convective severe weather season in the U.S. Severe weather during the month of March was practically non-existent until the last week of March. The first severe thunderstorm watch of March 2015, and only the fifth of the year was issued for the afternoon and evening of March 24th in eastern Oklahoma, northwest Arkansas, and the southwestern quarter of Missouri. This was the latest first March watch since 1970. Thunderstorms developed as forecast, and when all was said and done there were 70 reports of severe hail (1.00 inch or greater), with three reports of two-inch hail. There were no reports of high winds with these storms.

 


The atmosphere was a little more primed for severe weather on March 25th, and the Storm Prediction Center had a Moderate Risk of severe weather across central and northeastern Oklahoma into extreme southwestern Missouri and northwestern Arkansas.

Storm Prediction Center outlook issued at 11:30 a.m. CDT March 25, 2015

This time the storms were more widespread and spawned a more springlike menu of hail, damaging winds, and tornadoes. There were a number of reports of hail between two and three inches, and one report of 4.5 inch hail in Tulsa.



The bigger news from this event was the tornado that hit Moore, OK. Yes, this is the same Moore, OK that was devastated by a massive EF-5 tornado on May 20, 2013. This time Moore fared a lot better. There was some low-end EF-2 damage, but most was EF-0 to EF-1. A recap of this event, including video, photos, and maps, is available at the Norman, OK National Weather Service office web site.

Those two days were followed by a few days of relatively quiet weather. On March 31st an area of Slight Risk was painted from northern Texas and southern Oklahoma eastward across Arkansas into west central Alabama. There were many reports of hail and high wind but fortunately no tornadoes. Tornado warnings were issued yesterday afternoon for a storm moving through Arkansas but there were no touchdowns, although a funnel cloud was reported by a spotter.



There will continue to be a slight risk of severe thunderstorms through Friday as the cold front now moving into the central U.S. moves to the east coast. Showers and thunderstorms will return to the Midwest and lower Great Lakes next week as a frontal system stalls across the northern U.S.

Tuesday, March 24, 2015

Cloud "Mystery" Solved

If you are interested in weather phenomena and like a good detective story, then this is for you.

About two weeks ago people noticed strange cloud formations in the skies above San Antonio, TX. A deck of altostratus clouds were moving across the area, and people noticed wide, winding openings in the cloud deck and in some cases large circular openings. Photos began being posted to the NWS San Antonio Facebook page with inquiries about what caused these unusual formations.


Cloud formation seen above San Antonio on March 13, 2015


The phenomenon is known as "hole punch" clouds, or fallstreak holes. They are not that uncommon, especially near major airports and along air traffic routes, but the conditions have to be just right for them to occur. What happens, in simple terms, is that aircraft cause precipitation to occur as they fly through these clouds of supercooled droplets. The precipitation falls out of the cloud, but evaporates in the typically dry air underneath. When the cloud layer is thin and there is no supply of moisture to replace that which precipitated out, a hole remains.  The wispy streaks you often see beneath the hole are ice crystals precipitating out of the cloud. The difference between a "canal" in the clouds or a circular hole depends on whether the aircraft was cruising through the cloud layer or descending or ascending through the layer.

This is a photo of a "hole punch" cloud I took over western Indiana
on October 17, 2014

What is really neat about the San Antonio occurrence is that the forecasters at the National Weather Service, through a little "detective" work, were able to determine which individual airplane caused these hole punch clouds using sounding, satellite, and air traffic data! You can read the details about "The Mystery of the 'Cloud Hole Punch'" at the NWS San Antonio web site.

There is also more information about hole punch clouds at from NASA at this link. Some striking photographs and more explanation of hole punch clouds can be found at EarthSky.

There are more spectacular photos and explanation on the Cloud Appreciation Society web site. Keep your eyes to the sky - you never know what you may see.

Wednesday, March 11, 2015

The Yin and Yang of the Winter of 2014-2015

Yin and yang. Warm and cold. Buried and barren. Winners and losers.

There are a number of ways to describe this past winter, but my pick for a description would be something along the the lines of "sudden and weird".

The winter of 2013-2014  was a severe winter in many parts of the country, especially in the Northern Plains, Great Lakes, Midwest, and parts of the Northeast. Winter weather settled in during December and it was pretty consistently cold and snowy in the aforementioned areas until mid-March. Winter was relentless.

This year, however, Old Man Winter toyed with us. A typical first 10 days of November gave way to record cold and snow . On November 17 more than half of the lower 48 states had snow on the ground and was the highest level for the season until January 4.  Then came December, which was warmer than average across the entire country. The northern and central Rockies, some Great Lake snow belts, and western Maine were the only areas to see average to above average snowfall.
 

January's temperature departure pattern had hints of the warm west, cold east pattern that ultimately defined the winter. Snow was above normal in the northern Rockies, the southern Rockies, higher elevations of Arizona, New Mexico, and west Texas through the first three weeks of the month. Other than the dramatically cold and snowy weather for a couple of weeks in November, winter failed to materialize for much of the country.




Mean 500 millibar pattern
for January 24-February 28, 2015
Everything changed the last week of January. A building upper level ridge in the western U.S. was complemented by a deepening trough over the central and eastern U.S., a pattern that would remain more or less the same through February. For much of the country east of the Mississippi River winter began that week, and it came in at full speed with no let up. The start of that week saw much warmer than normal weather extended into the northern Plains under a building upper ridge, while to the east the stage was being set for the first of what would be several major snowstorms of the season to hit the Northeast.

For the six-week period ending March 7 snowfall was much above normal in a wide band from the southern Rockies eastward to the Carolinas, north to the southern Great Lakes and northern New England. Late February and early March storms brought one to two feet of snow to Kentucky, and damaging ice storms from Tennessee east to the Carolinas and south into the northern Gulf States.



February was an incredibly cold month for the country east of the Rockies, with temperatures averaging 10 to 18 degrees below normal across the northeastern third of the country. There were 23 states that recorded a top-ten coldest February. Much warmer and drier than normal weather continued over the western U.S. with record warmth in six states.





For the period beginning December 1 snow cover across the U.S. reached it's season low on December 12 at 17.5 percent. (It had dropped to 16 percent on November 24 after the mid-November peak of 50.4 percent). It rose to 53 percent on January 4, then fluctuated up and down before dropping to 21 percent in early February. The storms the last three weeks of February led to a peak snow cover of 63.4 percent on March 1.

Chart showing percent of U.S. (lower 48 states) covered by snow each day since November 1.

Today, after several days of mild weather and some rain, snow cover has plunged to 16.1 percent. Much of that snow cover is in the Northeast which is still 98 percent snow covered with an average depth of 21 inches. It will be a few weeks before the last vestiges of the Sudden Winter of 2014-2015  disappear from the landscape there.


Snow depth and extent on March 1, 2015 (left) and March 11, 2015 (right).
Source: NOAA National Operational Hydrologic Remote Sensing Center

Tuesday, February 24, 2015

Hang On - The Icy Grip of Winter Is Not Ready to Let Go

For those winter-weary folks who are ready for spring, it looks like you will have to hang in there a little longer.

This has been an unusual winter so far in most parts of the country. It got off to an unseasonably early, cold, and snowy start in November. By mid December it was clear that winter was pretty much a no-show for much of the country. December temperatures were above normal across the country, and snowfall was below normal in many locations, especially the Northeast.
 

 The first three weeks of January were colder than normal across the eastern U.S., but snow was surprisingly lacking. The locations with higher than normal snowfall were Arizona and New Mexico, the northern Plains and Rockies, and the snow belt areas around the Great Lakes.



So for the most part, real winter weather has only been with us for about four weeks. The four weeks of unrelenting cold, snow, and ice in the Northeast and the cold, snow, and ice in the southern Midwest and Southeast seems like it been around a lot longer. 


Snow cover across the U.S. was at a season-high 53.4 percent this morning. The continuous flow of Arctic air into the central and eastern U.S. has hastened the ice formation on the Great Lakes. It stands at 85.9 percent as of Monday, compared to 38.6 percent at the end of January, and 61.9 percent at this time last year. Last year ice cover on the Great Lakes peaked at 92.5 percent on March 6, the second greatest amount since the maximum of 94.7 percent in 1979.



Minimum temperature records were shattered across the eastern Midwest and Northeast yesterday morning and this morning, too numerous to list. Subzero temperatures occurred as far south as the Ohio River and east to Maine. Some of the coldest air was in east-central and central Illinois, and in northern New York through New England. It dropped to -20°F in Neoga in the south-central part of Illinois. Montpelier, VT set a new record low of -23°F. The lowest temperature in the lower 48 this morning was -34°F at Mount Washington, NH.

Minimum temperatures for the 12-hour period ending at 6:00 a.m. CST February 24.

The latest storm system that began over the weekend in the Southwest and affected the Rockies and all the way through the Deep South with snow and ice is moving out to sea off the Carolinas. It left two to three feet of snow in the Arizona and Colorado mountains and snow from Texas to North Carolina. Freezing rain glazed parts of Texas, Oklahoma, Alabama, and Mississippi. Sleet affected locations as far south as Louisiana and Mississippi.


72-hour snowfall ending the morning of February 24.

The 6-10 day and 8-14 day outlooks issued by the Climate Prediction Center today don't have a lot of good news for the winter-weary. Temperatures are likely to be below normal over much of the country through the first 10 days of March.

6-10 day (left) and 8-14 day (right) temperature outlooks issued February 24 by the Climate Prediction Center.

In addition, over the weekend one weather system could bring snow to much of the Midwest, and on Tuesday and Wednesday the Midwest, Ohio Valley, and Tennessee Valley may see rain or a wintry mix of precipitation. Both systems bear watching, so stay in touch with the forecast from your local National Weather Service office.

 (Left) Quantitative precipitation forecast for the period from 6:00 p.m. CST Friday, February 27 to 6:00 p.m. Sunday, March 1.  (Right) Quantitative precipitation forecast for the period from 6:00 p.m. CST Sunday, March 1 to 6:00 p.m. CST Tuesday, March 3.

Thursday, February 19, 2015

Brrrutal Cold

Surface temperatures at 6:00 a.m. CST on February 19.
Low temperature records were falling from the upper Midwest to Florida this morning as the leading edge of a Arctic cold air mass surged as far south as the Gulf Coast and central Florida. Watertown, NY plunged to -36°F this morning, shattering the previous record of -24°F set in 1963. The temperature at Chicago's O'Hare International Airport dropped to -8°F this morning, beating the previous record of -7°F set in 1936. In addition, today's high temperature only made it 4°F, a record low maximum high for this date. The previous record was 9°F degrees in 1936. A record low (-24°F) and record low high (-4°F) were also set in Marquette, MI today. Record low maximum temperatures were set in Binghamton, NY (10°F), tied in Syracuse (11°F), broken at Bridgeport, CT (24°F), broken at Islip, NY (24°F), and on and on. A number of these locations in New York broke records on several days this week. Record low temperatures and record low maximum temperatures were set as far south as Alabama, Georgia, South Carolina, and northern Florida. Daytona Beach reached only 50°F today, a record low maximum temperature for today, breaking the previous record of 53°F set in 1958 and 1972.

The lowest temperature this morning in the lower 48 states was -42°F in Cotton, MN, about 36 miles north of Duluth. Duluth's high temperature of -5°F today tied the record low maximum first set in 1941.

Minimum temperatures for the 12 hr period ending at 6:00 a.m. CST February 19.


Surface temperatures at 3:00 p.m. CST February 19.


The wide extent of the cold air is due to a huge upper level trough over the eastern two-thirds of the country. As can be seen on the chart below, the air, which flows parallel to the lines on the map, is coming straight over the Arctic and into Canada and the U.S.

500 millibar map for 6:00 p.m. CST February 19.


More records are likely Friday morning especially across the eastern U.S. where clear skies and snow cover will allow the temperature to plummet. Clouds spreading across the Midwest will slow the temperature drop there. Hard freeze warnings are in effect from southern Alabama through the northern half of Florida.


Forecast minimum temperatures for Friday, February 20.

While the intensity of the cold air is bad enough, the persistence of the cold air is a real problem for an area from the Ohio Valley southeast into Tennessee, Georgia, and western North Carolina where freezing rain from the storm earlier this week caused power outages. Unfortunately, it appears that more icing could occur this weekend from Ozarks east through Tennessee into North Carolina and Virginia.

Forecast for the period from 6:00 p.m. CST February 19 to 6:00 p.m. CST February 22.
It's likely that colder than normal weather will continue through the rest of the month for the eastern half of the U.S. The weather will moderate some next week, but temperatures will still be well below normal.

Minimum temperature forecast for Thursday, February 26.


Tuesday, February 17, 2015

New England, Canadian Maritimes Get PHD in Snow

That's PHD as in "piled higher and deeper".

The amazing thing about this winter is that the winter pretty much has been compressed into the last three weeks. In 1995-1996 Boston's record snowfall of 107.6 inches accumulated beginning in November and ending in April. This year that same amount of snow has almost accumulated in the last three weeks.

Last week about this time Boston had tallied 78.5 inches of snow for the season, but another foot has been added to that since then. As of today the season's snowfall for Boston was up to 96.0 inches, just 11.6 inches short of the record snowfall in 1995-1996. All but 5.5 inches of that, 91.5 inches, has fallen in the past 25 days. South of Boston snow amounts are higher, with Blue Hill up to 109.3 inches (more than 9 feet!)since January 24. The season total at Blue Hill stands at 131.4 inches. AS of today there was 36 to 42 inches of snow on the ground in Plymouth, Suffolk, and Norfolk counties in Massachusetts. Up the coast in Eastport, ME our CoCoRaHS observer there reported 78.5 inches on the ground today.

Snow piled up along the right field wall in Fenway Park in Boston.
Photo credit:  Jim Cantore via Twitter

You can see some spectacular "before and after" photos of  the snow in Boston in this Mashable article.

While a lot of attention has been on New England, the Canadian Maritime provinces have been getting hit just as hard by the snow. Three to four feet of snow blanket New Brunswick, and CoCoRaHS observers on Prince Edward Island reported as much as 55 inches (140 cm) of snow on the ground today.

Snow depths on February 17 for New England and Canadian Maritime provinces, including CoCoRaHS observations.

Digging out in Summerside, Prince Edward Island.
Photo from Twitter


8-14 day temperature outlook
All indications are that the cold weather will continue through the end of the month for the eastern half of the country. There appears to be a chance of snow every few days in the Northeast and New England, but right now nothing major appears to be in the cards. It looks like the expanse of cold air over the eastern two-thirds of the country will suppress the storm track south of New England keeping any major lows from developing off the New England coast. That's not to say it won't snow, but hopefully snowfalls will be measured only inches and not in feet. There is little doubt in my mind that Boston and many other locations will set new season snowfall records this year.



U.S. snow cover has jumped to almost 49 percent after the storm that affected the Midwest, mid-Atlantic, and Southeast yesterday. It had been down to 24 percent on February 14. What is also evident on the map is the lack of snow in the western U.S., but that's another story.





Thursday, February 12, 2015

Buried in Boston

Last week I wrote about the incredible amounts of snowfall in the Northeast, especially in Downeast Maine. Since last week's post Eastport has picked almost another foot of snow. Winter's onslaught has not let up, and this week Boston takes the spotlight.

The Boston area has received more snow in the past two and a half weeks than most locations, outside of the lake-effect snow belts, receive in one season. Winter really kicked in on January 24 with the blizzard, and it has been "pedal to the metal" ever since.  In the last week of January Boston's Logan Airport measured 31.7 inches of snow. In the first 11 days of February another 41.3 inches accumulated, bringing the total to 73 inches (more than six feet!) of new snow since January 24!  Boston set a record for the most snow recorded in a 30-day period, with 71.8 inches, breaking the record of 58.8 inches set in February 1978. The average season snowfall for Boston is 43.8 inches. The latest "frosting on the cake" was 14.8 inches of snow on Monday February 9, which tied the daily maximum snowfall record set in 2013. However, there were reports of 20 to 31 inches of snow at locations in Norfolk and Plymouth Counties south and southeast of Boston.


Daily snowfall for Boston since January 16, 2015 through February 12, 2015

The total snowfall in Boston so far this season is 78.5 inches, which is far from the record of 107.6 inches in the winter of 1995-1996. However, winter looks to be far from over.

The U.S. Cooperative observer at Blue Hill, MA, just south of Boston, tallied 36 inches of new snow the last week of January and another 47.7 so far this month, for a total of 83.7 inches!  Yesterday morning Blue Hill reported 38 inches of snow on the ground. CoCoRaHS observers around the Boston area are reporting anywhere from 26 to 39 inches of snow on the ground.

Snow depths reported by CoCoRaHS observers in Boston, February 12, 2015

Snow depth across the Northeast February 12, 2015.
Note that the highest amounts are along the Massachusetts and Maine coasts

Sledding off the roof in Boston.
Photo by Eric Fisher via Facebook.
If you have been following the news then you know that the snow has caused no shortage of problems in the Boston area. Collapsed roofs, awnings, and even entire buildings have occurred. Public transportation has been hampered, and the city has run out of places to put snow. City workers are trying to melt snow using large snow melters but can't keep up with the snow that has fallen.

Interestingly, winter in the Northeast was rather tame and mild up until January 24. Through January 23 Boston had received only 5.5 inches of snow, which at that point was 14.5 inches below normal. Temperatures were running near to slightly above normal. To give you an idea of how much things have changed in two weeks, take a look at this plot of the Accumulated Winter Severity Index (AWSSI) for Blue Hill, MA. The AWSSI is an index that a colleague, Barbara Mayes-Boustead, and I developed to measure the severity of a winter using readily available daily temperature and snow data. You can read more about this index here. What's interesting is that the plot of the index shows that the Boston area was bordering on a mild winter until January 24, but since then the winter has moved into the Extreme category (the top 20 percent of severe winters). The average AWSSI for the Boston area is 674, and the record (since 1950) is 1196 in the winter of 2002-2003. The value as of February 11 is 827.

Plot of the Accumulated Winter Season Severity Index for Blue Hill, MA.

Plot of the 2014-2015 AWSSI for Blue Hill. The solid black line is the average,
and dashed lines are one standard deviation above and below.

The steep climb of the AWSSI is likely continue based on the current upper air setup. A strong upper level trough is forecast to establish over the eastern two-thirds of the country, and that means a steady flow of Arctic air into the central and eastern U.S.

500 millibar forecast for 7:00 a.m. Wednesday, February 18.

6 to 10 day temperature outlook issued February 12, 2015
for the period February 18-22.

Disturbances moving through this trough are likely to result in storm development at some point next week, but exactly when and where is hard to pin down right now. However, the Quantitative Precipitation forecast chart for the 7-day period does show where it's possible that precipitation will fall and how much. You can follow developments on the NWS Weather Prediction Center website.
.
7-day Quantitative Precipitation Forecast for the period
7:00 p.m. EST February 12 through 7:00 p.m. EST February 20.


Since last week U.S. snow cover has dropped to 24.9 percent, but a significant portion of the snow is in the Northeast. It's not likely to go anywhere soon.