George BM

URGENT - WEATHER MESSAGE National Weather Service Baltimore MD/Washington DC 1140 AM EDT Tue Apr 21 2020 DCZ001-MDZ011-013-014-016>018-504-506-508-VAZ052>057-212345- /O.EXA.KLWX.FZ.W.0005.200422T0600Z-200422T1200Z/ District of Columbia-Southern Baltimore-Prince Georges- Anne Arundel-Charles-St. Marys-Calvert- Central and Southeast Montgomery-Central and Southeast Howard- Southeast Harford-Prince William/Manassas/Manassas Park-Fairfax- Arlington/Falls Church/Alexandria-Stafford-Spotsylvania- King George- Including the cities of Washington, Baltimore, Bowie, Suitland-Silver Hill, Clinton, College Park, Greenbelt, Laurel, Camp Springs, Glen Burnie, Annapolis, Severn, South Gate, Severna Park, Arnold, Odenton, St. Charles, Waldorf, Lexington Park, California, Chesapeake Beach, Huntingtown, Dunkirk, North Beach, Lusby, Prince Frederick, Bethesda, Rockville, Gaithersburg, Silver Spring, Columbia, Ellicott City, Aberdeen, Dale City, Manassas, Woodbridge, Lake Ridge, Montclair, Reston, Herndon, Annandale, Centreville, Chantilly, McLean, Franconia, Arlington, Alexandria, Falls Church, Falmouth, Fredericksburg, and Dahlgren 1140 AM EDT Tue Apr 21 2020 ...FREEZE WARNING IN EFFECT FROM 2 AM TO 8 AM EDT WEDNESDAY... * WHAT...Sub-freezing temperatures near 30 expected. * WHERE...Portions of The District of Columbia, central, northern and southern Maryland and central and northern Virginia. * WHEN...From 2 AM to 8 AM EDT Wednesday. * IMPACTS...Frost and freeze conditions will kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing. PRECAUTIONARY/PREPAREDNESS ACTIONS... Take steps now to protect tender plants from the cold. To prevent freezing and possible bursting of outdoor water pipes they should be wrapped, drained, or allowed to drip slowly. Those that have in-ground sprinkler systems should drain them and cover above- ground pipes to protect them from freezing. && $$

The DC metro is now within the SLGT risk. 0% Tornado/ 15% Wind/ 0% Hail

Don't completely sleep on this Tuesday either. There could be some low-topped convection with limited CAPE along and just ahead of the cold front. Steep low-level lapse rates and fairly fast-flow aloft could translate to some of the convection having strong wind gusts.

Down to at least 30F at IAD this morning. Patchy frost.

This shows that we at least have a non-zero severe chance through the end of April.

Wait a minute?... What?!

Even the April 6, 2017 had fairly widespread strong winds and seven EF-0 tornadoes in northern VA... this with less than 250J/kg MUCAPE. That June 13, 2013 event could have been a memorable event area-wide if the morning MCS didn't hamper things. It was also the last time we had a moderate risk in the immediate region though it was downgraded to a SLGT at 1630z due to said morning MCS leaving us with AOB 1000 J/Kg MLCAPE. This is my opinion (not an expert): When dealing with a W/NW flow event with a fairly strong low-pressure system within the flow there will very often be a morning/early day MCS. This is because the previous days storms that develop in the Midwest often grow upscale during the evening and are able to survive the whole night due to the better dynamics and CAPE. With the forward speed that these MCSs usually have they very often reach us during the morning hours. An ideal thing with these regimes would be either the timing being a few hours faster so that we can get more midday/solar noon sunshine to destabilize the atmosphere more quickly for any later day activity (easier option) or a heat-dome already being in place so that any morning event would stay to the north while the low-pressure system approaches from the W/NW spawning another MCS (or just decent storms in general) during the afternoon to cruise through the region during the afternoon/evening (harder to pull off option).

Thank you both for the replies.

Sorry for the novice question but how do I read this? Is this showing the expected surface wind speed and direction at various times?

Mesoscale Discussion 0360 NWS Storm Prediction Center Norman OK 0426 PM CDT Sun Apr 12 2020 Areas affected...south-central and southeast Mississippi Concerning...Tornado Watch 106...107... Valid 122126Z - 122200Z The severe weather threat for Tornado Watch 106, 107 continues. SUMMARY...Based on recent radar and environmental data, a violent tornado with potential peak winds of 170 to 205 mph (EF4-EF5) is likely ongoing. THIS IS AN EXCEPTIONALLY RARE EVENT. DISCUSSION...An intense supercell will continue to move through a favorable environment over south-central Mississippi, characterized by 0-1 km SRH around 400 m2/s2 and MLCAPE near 2000 J/kg per latest mesoanalysis data. Recent radar signatures from KLIX as of 2112Z reveal an intense supercell characterized by a 0.4 degree rotational velocity of at least 70 kt. A tornadic debris signature has also been noted on recent radar scans. These signatures are occurring in an environment characterized by STP greater than 7. Previous signatures within similar environments produced tornado-damage-estimated wind speeds from 170 to 205 mph and confidence is high for a likely violent tornado. A long-track tornado is expected to continue based on the rotational velocity duration and the storm moving within a favorable downstream environment.

Also RAP'd.

I know that the post-frontal winds may be strong but... though we are not expecting much of this atm pre-cold front can you imagine if we somehow got a break in the clouds late tomorrow morning with those kind of low-level winds overhead?... Of course this is more speculative than me predicting it.

Even the long-range 6z hrrr (Yes, all caveats apply... end of range) shows 45-50 kt post-frontal gusts across the region. I usually find the hrrr more in line with what happens during synoptic wind events during the daylight hours. All long-range caveats aside... it looks windy tomorrow.

A rare Day 3 update. Day 3 Convective Outlook AMEND 1 NWS Storm Prediction Center Norman OK 0211 PM CDT Sat Apr 11 2020 ...Virginia through central and eastern Pennsylvania and New Jersey... Have expanded the SLGT risk farther north into this region. Areas of rain and thunderstorms will likely be ongoing north of a warm front from PA and NJ into southern New England. This activity will shift northeast during the morning allowing modest destabilization to occur in the pre-frontal warm sector with MLCAPE from 400-800 J/kg. Storms are expected to redevelop along cold front and in association with deeper forcing accompanying the northeast-ejecting shortwave trough. Wind profiles with 50+ kt effective bulk shear along with large 0-1 km hodographs will promote a threat for organized storms including supercells capable of damaging wind and a couple of tornadoes.

@losetoa6 Start the thread! I have a weenie feeling about this one.

Psssst.... June 23rd is around the block.

Heads up seven up! URGENT - WEATHER MESSAGE National Weather Service Baltimore MD/Washington DC 813 PM EDT Wed Apr 8 2020 DCZ001-MDZ003>006-011-013-014-503>508-VAZ028-030-031-053-054-501- 505>508-WVZ052-053-090815- /O.NEW.KLWX.WI.Y.0008.200409T1400Z-200409T2100Z/ District of Columbia-Washington-Frederick MD-Carroll- Northern Baltimore-Southern Baltimore-Prince Georges-Anne Arundel- Northwest Montgomery-Central and Southeast Montgomery- Northwest Howard-Central and Southeast Howard-Northwest Harford- Southeast Harford-Frederick VA-Warren-Clarke-Fairfax- Arlington/Falls Church/Alexandria-Northern Fauquier- Western Loudoun-Eastern Loudoun-Northern Virginia Blue Ridge- Central Virginia Blue Ridge-Berkeley-Jefferson- Including the cities of Washington, Hagerstown, Frederick, Ballenger Creek, Eldersburg, Westminster, Reisterstown, Cockeysville, Baltimore, Bowie, Suitland-Silver Hill, Clinton, College Park, Greenbelt, Laurel, Camp Springs, Glen Burnie, Annapolis, Severn, South Gate, Severna Park, Arnold, Odenton, Germantown, Damascus, Bethesda, Rockville, Gaithersburg, Silver Spring, Lisbon, Columbia, Ellicott City, Jarrettsville, Aberdeen, Winchester, Front Royal, Berryville, Reston, Herndon, Annandale, Centreville, Chantilly, McLean, Franconia, Arlington, Alexandria, Falls Church, Warrenton, Purcellville, Leesburg, Ashburn, Sterling, Big Meadows, Wintergreen, Martinsburg, Charles Town, and Shepherdstown 813 PM EDT Wed Apr 8 2020 ...WIND ADVISORY IN EFFECT FROM 10 AM TO 5 PM EDT THURSDAY... * WHAT...West winds 20 to 30 mph with gusts up to 50 mph expected. * WHERE...The District of Columbia, portions of central and northern Maryland, central, northern and northwest Virginia and eastern West Virginia. * WHEN...From 10 AM to 5 PM EDT Thursday. * IMPACTS...Gusty winds could blow around unsecured objects. Tree limbs could be blown down and a few power outages may result. PRECAUTIONARY/PREPAREDNESS ACTIONS... Use extra caution when driving, especially if operating a high profile vehicle. Secure outdoor objects. && $$

I like sardines.

Just got some brief 35-40 mph wind gusts. Not much rain though as the line has really fallen apart. Now if timing was 12 hours later or earlier...

The "obviously overdone severe-weenie" 6z 3kNAM said we get a supercell through DC tomorrow afternoon.

Great news! May you and your relatives get through this time.

A pre-climo NW flow regime w/ potentially steep mid-level lapse rates... We watch.

Warning... it's within one hour. Northeastern areas will see the best sunset conditions.

Morning AFD from LWX. It's not often you hear this mentioned. The 12Z KIAD sounding has winds 35-40KTS in the boundary layer this morning. The inversion busted rapidly by 13Z across the region, with numerous wind gusts between 30-40MPH in the western suburbs of the Balt/Wash Metro Areas. Winds will temper a bit this afternoon as the pressure gradient aloft slackens. Inverted V soundings approaching super adiabatic, along with gusty winds and dry surface conditions, you might see a dust devil or two in the Shenandoah Valley during the midday hours.

This! It looked even more unreal in person. Mother Nature can truly be amazing and humble the biggest weenies! This was one of my favorite pictures from the chase.