Thursday, April 27, 2017

Can You Say "Pattern Change"?

Most of this spring east of the Rockies has been warm, coming on the heels of a mild winter. The growing season is running two to three weeks ahead of normal, but now Mother Nature is messing with us.

This week saw a lot of snow in the Rockies, not all that unusual even this late in spring. This morning flakes were flying in Minnesota and Wisconsin in the wake of a strong low and associated cold front.

Surface weather map at 1:00 p.m. CDT April 27. 2017

More snow is expected throughout the Rockies this weekend as cold air plunges south behind an intensifying low pressure system in the central Plains. This storm will be associated with an upper level closed low over the central U.S., one that will move very slowly over the weekend and early next week.

500  millibar level chart for 7:00 a.m. CDT Sunday, April 30, 2017

Heavy rain is expected this weekend from the Missouri Ozarks northeast through Illinois and Indiana. Severe weather is also likely from the southern Plains northeast into the Ohio River Valley. Flash flood watches are already in effect

Watches, warnings, and advisories in effect as of 9:00 p.m. April 27, 2017.

For the next week to ten days, and perhaps longer, the overall upper level pattern will be characterized by high pressure ridges off the west coast and the east coast, and a broad trough in the middle part of the country. That sets the stage for a cold, wet period for most of the U.S. east of the Mississippi River.

6-10 day temperature (left) and precipitation (right) outlooks from the Climate Prediction Center.

The next week is going to be a challenging one with heavy rainfall expected in the central U.S. CoCoRaHS rain gauges will get quite a workout from Oklahoma to Michigan and Nebraska east to Ohio. One thing to keep in mind when looking at these QPF maps is that this is a broad generalization of precipitation. The heavy amounts aren't uniformly distributed as these maps might indicate. "Precipitation doesn't fall the same on all."  (CoCoRaHS proverb). It certainly conveys the potential, however.

Quantitative Precipitation Forecast for the 7-day period ending 7:00 p.m. Thursday, May 4

After this weekend's system lifts out, another closed low is forecast to develop in the central U.S. late next week by one model.

500  millibar level chart for 7:00 a.m. CDT Friday, May 5, 2017

Wednesday, April 19, 2017

Weather Radio - A Must for Every Home

2017 severe weather reports.
We have already had a good bit of severe weather this season. Radar technology has improved with the advent of dual Doppler capabilities, and lead times for warnings have improved as well. Yet, there have already been 27 fatalities from tornadoes this year, and we are just getting into the peak of the season.

In the aftermath of storms we often see people interviewed who say "It struck without warning". What that statement usually means is "I wasn't aware of a warning", because in most cases a warning was not only issued, but issued with enough time to take shelter.  Everything from the forecast to the warning can be perfect, but if people aren't receiving the information then that information can't help them.

Outdoor warning sirens are exactly that. Their purpose is to warn people outside of impending severe weather, and are not intended to alert folks who are at home with the windows closed, the AC running, and the TV turned up.

The rapid development in phone technology means that those with cell phones can receive alerts of severe weather, provided the phone is on and you have it with you. What about in the middle of the night when you are sound asleep and a severe thunderstorm or tornado warning is issued?  The most reliable means of getting those warnings in time to take cover is a weather alert radio.

The NOAA Weather Radio All Hazards web page contains everything you need to know about NOAA Weather Radio, including consumer information about the radios, how to program your radio, and listing of radio frequencies and their status by county for every state. NOAA weather radio is even established in Puerto Rico, America Samoa, the U.S. Virgin Islands, Guam, and the N. Mariana Islands.

Weather radios come in portable models that you can take with you to outdoor events or other activities like hiking or camping. Some have crank and/or solar recharging capabilities. Desk models run on AC power with battery backup.  The prices of radios range from $25 to $135, with most desk models in the $40 to $75 range. One feature you should seriously consider is a radio with SAME (Specific Area Message Encoding) capability.  This allows users to receive messages only for their designated county or counties of interest rather than the entire broadcast area. This is especially nice at night, as your radio alert will not be activated for areas you have not selected. On the basic radios without SAME, any alert issued for any area covered by a specific transmitter will be triggered on the radio. Note that the weather radio program is officially the NOAA All Hazards Weather Radio. In addition to severe weather, NWR also broadcasts warning and post-event information for all types of natural, environmental, and public safety hazards.
My weather radio - ready and waiting.

There are only seven VHF frequencies used for NOAA Weather Radio transmissions in the U.S.

Weather radio frequencies in the U.S.

NOAA All Hazards Weather Radio coverage in the U.S.

NOAA Weather Radio broadcasts are also available via live streaming over the web.  A group of home weather station operators, website owners, CoCoRaHS volunteers, and spotters have developed a web site to live stream NOAA weather radio broadcasts across the country. This will not replace a weather radio in your home since there is no alerting capability, but it is a convenient way to access the broadcasts for other parts of your state or the country. The list of stations also include three from Canada. Visit for more information and to listen to live streams.

NOAA Weather Radio stations current available for live streaming on

Weather radio receivers will also work in Canada. Environment Canada, the government agency responsible for producing official forecasts, operates a network of "Weatheradio" transmitters which generally operate on the same frequencies as the U.S. NOAA Weather Radio network. More information on weather radio in Canada can be found here.

A weather radio should be in every home, just like a smoke detector. It should be located in a spot where you can hear it at night, preferably in the bedroom. Without being too dramatic - you're life could depend on it.

Thursday, April 13, 2017

Hail - It's in Our Name

CoCoRaHS' annual Hail Week is coming to a close. If you have been following this week's messages of the day you have seen how to measure hail, report it, and how to make a hail pad. Hail is a fascinating phenomena and there is a lot of information available if you want to learn more about it. The CoCoRaHS Hail page  has some information, and you can find a lot more information at Living With Weather- Hail on the Midwestern Regional Climate Center website.

This year's hail season was off to an early start with quite a few large hail events from late February on. Normally probabilities for significant hail very low at the end of February and only begin to ramp up in mid-March to early April. Here are the climatological probabilities for significant hail from the the NOAA Storm Prediction Center. The center of the high probabilities moves north through April and May, reaching a peak in late May. By early August probabilities are diminished and continue to diminish into early fall.

This year, hail has been frequent. So far CoCoRaHS observers have submitted hail reports on 65 of 102 days so far this year,just slightly ahead of last year's pace.  This map is a compilation of hail reports for the year to date from the Storm Prediction Center.

There have been some impressive and damaging storms so far this spring. What's caught my attention are the number of significant hail events (hail 2 inches or more) that have been reported.

Hail photo credit Keri Bentley

 More baseballs in Texas on March 26.

Hail in Double Oak, TX on March 26.
Credit: @WxChaserBryan on Twitter

A nice assortment of hail sizes in eastern Illinois on March 20 .

Finally, not all hail falls as nice round balls. Here is a photo of some spiked hail that fell in Bolivar, TN on March 27.

Hail in Bolivar, TN on March 27.
Photo by Cynthia Thrasher Dickerson

Measuring hail is a core mission of CoCoRaHS, and the separate hail reports on the CoCoRaHS web site allow you to submit your hail information. There are a few things you need to know before measuring hail, and you can find that information in our "Measuring Hail" training animation. Here is a hail size reference and measuring guide you can download, print, and laminate for use. The rule on the bottom is to scale and fits on a 3x5 card. Make multiple copies and keep one at home, in the car, or at work.