Wednesday, January 7, 2015

An Eventful First Week of January

January 2015 is off to a rousing start in the weather department based on what's happened this first week.

On January 1st record cold affected the southwestern U.S. from California east to Texas.  Then a day later a very strong cold front swept through the Hawaiian Islands producing damaging winds at the surface and blizzard conditions near the summits on the Big Island.

As the system that brought cold and snow to the southwestern U.S. moved east and northeast on the 2nd and 3rd, it drew moisture from the Gulf of Mexico to produce 3 to 6 inches of rain from eastern Texas and Louisiana through central Arkansas. Severe thunderstorms erupted ahead of this system in the southeast, producing at least four tornadoes and wind damage from southeastern Alabama across southern Georgia.

Total precipitation for the period January 1-7, 2015

A clipper system brought snow to a wide swath of the northern and central U.S. this first week. Snow accumulated  across much of Montana, with 12 to 18 inches in and around Billings. As this system moved southeast snow spread from the Dakotas across Iowa, the northern two-thirds of Illinois, Indiana, Michigan, and to the mid-Atlantic coast. Several inches of snow falling during the morning rush hour tied Washington DC traffic into knots.

72-hour snowfall ending the morning of January 7, 2015

At the end of this week snow covered about 46 percent of the lower 48 states, the highest since the unusual snow in mid-November.

Snow depth on January 7, 2015

Finally, a massive Arctic high pressure system dropped into the northern U.S. early this morning.

Surface weather map at 9:00 CST January 7, 2015

Temperatures at 9:00 a.m. CST January 7, 2015
The strong pressure difference between the high and a low over southern Quebec/New England produced bone-chilling winds across the eastern half of the U.S., prompting wind chill warnings for parts of the Midwest and Northeast, and wind chill advisories for most of the remainder of the eastern half of the country. Hard freeze warnings are in effect for tonight and tomorrow morning along the Gulf Coast from Houston east to northern Florida. Blizzard warnings are in effect for Thursday for northeastern North Dakota and northwestern Minnesota, and a blizzard watch for northeastern South Dakota.
Watches, warnings, and advisories in effect as of 9:00 p.m. CST January 7, 2015

The cold Artic air streaming across the Great Lakes has switched on the lake-effect snow machine, and it will continue for the next 36 to 48 hours.

Satellite visible image of the Great Lakes today at 1:15 p.m. CST. The flow of cold air across the Great Lakes can be clearly seen in the bands of clouds in and downwind of the lakes. The dark areas are clear skies on the lee side of the lakes.

A CoCoRaHS observer near Watertown, New York (NY-JF-25, Watertown 1.3 WSW) reported 23.5 inches of new snow for the 24 hour period ending at 4:30 a.m. EST this morning. Watertown is located at the east end of Lake Ontario.

CoCoRaHS snowfall map for northern New York for the morning of January 7.

So how strong is the high pressure system? Very strong - high pressure records were set in a number of locations in the central and northern Plains today. Aberdeen, South Dakota reached a pressure of 1055.4 millibars (31.17" of mercury) this afternoon, a new record at that location.

Photo of the barograph (recording barometer) at Aberdeen, SD today. The actual air pressure was literally "off the chart". Photo credit:  NWS Aberdeen, SD
Omaha's air pressure reached 1055.3 millibars today (31.16 inches), breaking the old record 1053.7 millibars (31.12 inches) on December 22, 1989. A new record was also set at Grand Island, NE. It's likely that by tomorrow we will be seeing a number of reports of new record high pressure readings that occurred in the Plains today.

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