southmdwatcher

https://weather.cod.edu/text/ DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1221 AM CDT SUN APR 12 2020 VALID 131200Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN GEORGIA...THE CENTRAL AND EASTERN CAROLINAS AND VIRGINIA... ..SUMMARY SEVERE THUNDERSTORMS WITH TORNADOES, DAMAGING WIND GUSTS AND HAIL WILL BE LIKELY ACROSS PARTS OF THE ATLANTIC COASTAL PLAINS INTO THE CENTRAL APPALACHIANS ON MONDAY. ..ATLANTIC COASTAL PLAINS/CENTRAL APPALACHIANS A POTENT SHORTWAVE TROUGH WILL MOVE QUICKLY NORTHEASTWARD ACROSS THE OHIO AND TENNESSEE VALLEYS TONIGHT. THE TROUGH SHOULD BE POSITIONED OVER THE CENTRAL APPALACHIANS AT THE START OF THE PERIOD. AT THAT TIME, A 70 TO 80 KT LOW-LEVEL JET WILL BE LOCATED ACROSS THE CAROLINAS AND VIRGINIA WITH AN AXIS OF MODERATE INSTABILITY CO-LOCATED WITH THE JET. A BAND OF CONVECTION, POTENTIALLY SEVERE, IS FORECAST TO BE IN NORTHEAST GEORGIA, THE WESTERN CAROLINAS AND WESTERN VIRGINIA AT 12Z. OTHER STRONG THUNDERSTORMS MAY BE ONGOING IN THE UPPER OHIO VALLEY. AN 80 TO 100 KT MID-LEVEL JET ORIENTED ALONG THE WESTERN EDGE OF THE LOW-LEVEL JET WILL CREATE VERY STRONG DEEP-LAYER SHEAR FAVORABLE FOR SEVERE THUNDERSTORMS. THIS BAND OF CONVECTION IS FORECAST TO MOVE QUICKLY EASTWARD ACROSS THE ATLANTIC COASTAL PLAINS DURING THE MORNING AND EARLY AFTERNOON. THE MAIN QUESTION WITH THIS OUTLOOK IS CONVECTIVE MODE. THERE ARE TWO POSSIBILITIES. THE FIRST IS THAT THE BAND OF THUNDERSTORMS WILL HAVE DISCRETE ELEMENTS AND GAPS THAT WILL BE FAVORABLE FOR SUPERCELLS AND TORNADOES. FORECAST SOUNDINGS AT 15Z FROM SOUTHERN VIRGINIA SOUTHWARD INTO NORTHERN SOUTH CAROLINA SHOW LOOPED HODOGRAPHS WITH 0-3 KM STORM RELATIVE HELICITIES IN THE EXTREME CATOGORY, GENERALLY NEAR OR ABOVE 600 M2/S2. THIS WOULD SUPPORT A THREAT FOR STRONG TORNADOES ASSOCIATED WITH THE MORE DOMINANT SUPERCELLS. A WIND DAMAGE AND HAIL THREAT WOULD BE LIKELY WITH SUPERCELLS AND WITH THE MORE ORGANIZED LINE SEGMENTS. THE SECOND SCENARIO WOULD BE THAT A SQUALL-LINE IS ONGOING AT 12Z FROM EASTERN GEORGIA NORTHWARD INTO THE WESTERN CAROLINAS AND VIRGINIA. IN THAT CASE, WIDESPREAD WIND DAMAGE WOULD BE LIKELY. A QLCS TORNADO THREAT WOULD EXIST WITH THE STRONGER BOWING LINE SEGMENTS. HAIL WOULD ALSO BE POSSIBLE WITH THE MORE INTENSE PARTS OF THE LINE. AT THIS TIME, THE OUTLOOK REFLECTS THE FIRST SCENARIO IN WHICH MORE DISCRETE CELLS ARE PRESENT ACROSS THE WARM SECTOR AT 12Z. IN THIS CASE, A CLUSTER OUTBREAK OF TORNADOES WOULD BE POSSIBLE AND A STRONG LONG-TRACK TORNADO OR TWO CAN NOT BE RULED OUT. ..BROYLES.. 04/12/2020

That will be fluid tomorrow, I expect the northern extent to change again and some portion of the Enhanced area may go to Moderate for tornadoes.

Lapse rates were not great at 18z, but everything else looked primed. Maybe we get another great parameter day that just misses one ingredient. Two rounds of potentially severe storms are quite possible for central and eastern parts of our region.

At 18z those wind fields with 800-1400 ML CAPE

I hope that is not what pans out. That could be ugly for someone around here.

Just as an example......April 15, 2011 in MS/Alabama was a Moderate risk. That day had a messy storm mode for portions of those states, but could have verified High Risk in southern MS/AL. The system was a bit slower than forecasted. April 16th was a doozy of a day in SE VA and NC. A tamer version of that could be what we what we should look for and no High Risk for NC. Exceptional shear busted up the QLCS late morning in NC that day and allowed convection to become discrete south of the existing rain cooled boundary. Also we have the chance for supercells to form in the dry slot early afternoon.

We will also likely have a period of strong to damaging winds after the frontal passage.

I could possibly see outlook upgrades for DC/Baltimore area and southward through the Carolina's. However, don't expect any decisions until the early Monday morning SPC cycle.

12z European looks to be on board for some severe weather Monday

The upper low that was over San Diego area last night has moved to northern tip of Gulf of California/south of Yuma AZ at the moment.....still looking like this could have the slower timing. Watch how that piece progresses eastward.

0z NAM is bringing the warm sector even further north, on the west side of the Appalachians. 12-15z Monday is looking very stormy around here...mid 60's dew points ML CAPE around 500 and still a significant wind field overhead.

Monday morning is the time frame to be worried about tornadoes and or really severe wind fields, and there is CAPE to work with especially south and west of DC. That assumes the timing of this system does not slow down any further.

If that 925mb GFS wind field ends up verifying and shifts west, that could be a bit of an issue

I know this is way out there for the NAM but it is trending slower and further west and the Euro has also been slower with the Sunday/Monday severe weather event...wherever that is centered.

The sun is going to try to come back, today this is one of the rare events in this region where the sun is not needed but can certainly aid the environment overnight...I am already looking forward to Sunday's event southwest of here and what here could be an overnight storm scenario. Hope the Euro and UK are wrong about Sunday down South.

Well now that is quite a broad area of Slight Risk now for tomorrow. Salisbury to Baltimore to north of Pittsburgh and southwest are now included. 2 Tor 15 Wind 15 Hail for our whole region.

The NFL will be the front runner in the social media community with all that is in front of them to be public.

At this point let's just have a few tornado outbreaks regionwide in the next two months and be done, the pattern is screaming severe weather events if it continues in this manner.

Steady snow now and slush is starting to accumulate on elevated surfaces.

Just warned....winds are strong here in southern St. Charles

Ummm there are some couplets in southern Charles County on TDCA and TADW.....none are warned

Looks like we are getting more unstable than those early morning outlooks forecasted. The sun is breaking through in Alexandria as well.

That is a very large 5% Tornado risk area

1.39" for the event, and 5.57" for October. Nice recovery from the dry Summer.

0.46" since 8am and 0.85" total so far. Moderate rain continues.