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Saturday, March 19, 2011

March 19 Plains and Midwest Heavy Snow Forecast Discussion

This is a forecast discussion concerning a potential snowstorm in the Plains to the Midwest areas March 22-24.
FORECAST DISCUSSION
The DGEX model, an extension of the NAM model, has been consistent in telling of a snowstorm that could very well be the last storm of the 2010-2011 winter season. It shows a strong low tracking through Central IL, giving many Wisconsin areas an extreme amount of snow in very little time.
The GFS is taking a warm solution. It pulls the low through North Illinois.
The ECMWF model also goes through North Illinois.
With two major models leaning against a fairly discounted model, I will have to wait and see what happens. There definitely is potential.

March 19 North Illinois Heavy Rain Forecast Discussion

FORECAST DISCUSSION
This is a Forecast Discussion for a heavy rain event in North Illinois tomorrow.
What we will have here are low pressure systems pumping rain and warm air into the North Illinois area. This forecast discussion is based off of the latest run of the University of Illinois WRF model.
So first, we will start off with the ensemble reflectivity, meaning what is predicted to show up on radar.
This image I chose out is to show the potential of a severe component that the National Weather Service may not be recognizing. By the looks of the initial red line, there could be a small piece of bow echo in there. Overall, this shouldn't be a severe event, but based on this image, I wouldn't be surprised to see some gusty winds or small hail.
This next image is definitely more organized as a multi-cell storm complex. This is a more concerning image, as the abundance of strength in this complex is startling. This looks like much more of a contender for a severe weather event, and I would expect this scenario to produce gusty winds, cloud to ground lightning and hail.
This image is more of an ending piece, as in the backside of this storm. By now, this complex appears to have weakened and coincides with the first image. I will definitely be watching for either this scenario of two areas of strong storms or one big strong multi-cell complex.
Next up, we will focus on total precipitation from University of Illinois Ensembles.
This is a total precipitation estimate. The ensembles aren't handling the swath of heaviest precipitation well, so I will continue to monitor these. Anyways, this image puts the swath of rain through the Northern Illinois area, with totals potentially up to 2 inches in some areas.
This second image is a much more humble precipitation outcome, with not as heavy precipitation in the biggest area of rain and storms. However, there is agreement in between this image and the above image that the heaviest precipitation should be across the North Illinois area.
This has been a forecast discussion. Another one on this event may be issued later.

Severe Weather Situation #009

This is Severe Weather Situation #009.
Severe Thunderstorms are currently occurring in Oklahoma and Southeast Kansas.
The Storm Prediction Center has issued a Mesoscale Discussion in the image above. Severe Thunderstorm potential will exist in isolated spots over Northeast Kansas, which may expand across Missouri this afternoon. As these storms move out, The Weather Centre will be monitoring how often these storms pop up and where they will be moving.
This is the real-time radar as per the Storm Prediction Center. Included are severe weather risks and watch boxes. Blue boxes= Severe Thunderstorm Watches. Red boxes= Tornado Watches.

March 19 All Day Severe Weather Situation #008 Update #1



URGENT - IMMEDIATE BROADCAST REQUESTED    SEVERE THUNDERSTORM WATCH NUMBER 51    NWS STORM PREDICTION CENTER NORMAN OK    945 AM CDT SAT MAR 19 2011        THE NWS STORM PREDICTION CENTER HAS ISSUED A    SEVERE THUNDERSTORM WATCH FOR PORTIONS OF                SOUTH CENTRAL AND SOUTHEAST KANSAS           EXTREME WESTERN MISSOURI           NORTHERN OKLAHOMA        EFFECTIVE THIS SATURDAY MORNING AND AFTERNOON FROM 945 AM UNTIL    400 PM CDT.        HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70    MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.        THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 85    STATUTE MILES NORTH AND SOUTH OF A LINE FROM 55 MILES WEST    SOUTHWEST OF WICHITA KANSAS TO 25 MILES EAST NORTHEAST OF JOPLIN    MISSOURI.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE    ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).        REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE    FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH    AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR    THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS    AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY    DO PRODUCE TORNADOES.        DISCUSSION...THUNDERSTORMS HAVE BEEN INCREASING IN COVERAGE AND    INTENSITY OVER NORTHERN OK/SOUTHERN KS THIS MORNING AS A SHORTWAVE    TROUGH OVER CO/NM APPROACHES.  STEEP MID LEVEL LAPSE RATES AND    SUFFICIENT ELEVATED CAPE WILL PROMOTE A RISK OF HAIL IN STRONGER    CELLS THROUGH MID AFTERNOON.

March 19 All Day Severe Weather Situation #008

This is a follow-up to the Severe Weather Situation #007.
Above is the SPC radar return with risk areas.
Radar returns indicate the strongest storms may be developing at this time. Pop-up Storms are developing in Oklahoma and Kansas. I do feel the slight risk area will need to be expanded north to account for those pop-up storms.
12z RUC indicates moderate instability by Best Lifted Index in east Oklahoma into extreme southern portions of Kansas.
Most Unstable CAPE values are around 1000 j/kg in the designated areas, indicating an atmosphere that is still in some control of itself.
Will monitor this situation and issue more follow-ups if necessary.

UPDATE 9:51AM CDT
A severe thunderstorm watch has been issued for the area in the above image in blue.

March 19 Severe Weather Forecast Discussion

This is an image of the 4-8 day probability for severe weather.
FORECAST DISCUSSION
The image above is the risk for severe weather 30% or above in the next 4-8 days. When you get a 30% risk, you begin to get into some hot water in the weather world. 30% basically means severe weather will happen and it could happen with strength.
Day 4 (D4), we see a risk area over the Plains into the Midwest. It is shaped in the form a bow echo storm would usually have.
That said, The Weather Centre is definitely eyeing the possibility of a bow echo storm. Should a bow echo develop, it would have potential to cause damaging winds.
The 6z GFS is even pointing at the prospect for a squall line after reviewing the Best Lifted Index images. However, there will be the Canadian air mass that will fight quite hard to keep the severe weather away from the Great Lakes and Ohio Valley. However, that air mass suddenly retreats, leaving the door open for the squall line to come through. However, it does weaken as it comes through, which many of the models have shown.
In Day 5, that squall line suddenly gets a second wind and fires up with more instability in the Ohio Valley. I am unsure of what type of storm it will be, but likely not a squall line or a bow echo. I would anticipate pop-up storms, possibly coming together to form a multi-cell storm complex.

Severe Weather Situation #007


This is Severe Weather Situation #007.
Severe Thunderstorms are forecast to occur this morning into this afternoon in the Oklahoma area.
At 8:09pm CDT... Radar detected thunderstorms developing in the Oklahoma Panhandle. The Weather Centre also indicated high Lifted Index values of -8 in a portion of Oklahoma (The 2nd image down).
A slight risk area has been warranted in the Oklahoma area due to the risk of these storms encountering this unstable atmosphere (First image).

Specific Concerns...
These storms are pop-up storms and will be hard to predict. However, unless you live in the area in the 2nd image down where the -8 circle is, you should be safe. But do keep an eye to the sky if you live in the -6 range.

March 19 9z RUC Best Lifted Index Forecast Discussion

This is an image of right now from the 9z RUC model.
FORECAST DISCUSSION
Weak area of moderate instability in Central Oklahoma providing breeding ground for strong to severe thunderstorms this morning into the afternoon.
At this time, thunderstorms have developed in West Oklahoma and are now moving east into Central Oklahoma.
Will definitely have to monitor the situation for several factors.
One is the image above of the Lifted Index. With values in the -8 range, the atmosphere is at least moderately unstable.
Another factor is Lapse Rate values. Right now at the time of this issuance, Lapse Rates were in the 8-8.5 region in Oklahoma. This provides more evidence of an unstable atmosphere.
This will be a situation to watch, and a Severe Weather Situation will be issued next.