2020 Mid-Atlantic Severe Weather - General Thread

[Eskimo Joe]

40% chance of a WW:  https://www.spc.noaa.gov/products/md/2020/md0294.html

Quote

NWS STORM PREDICTION CENTER NORMAN OK
0157 PM CDT TUE APR 07 2020

AREAS AFFECTED...NORTHEAST WEST VIRGINIA...NORTHERN VIRIGNIA AND
PORTIONS OF MARYLAND

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 071857Z - 072030Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...THE THREAT FOR SEVERE HAIL AND WIND IS EXPECTED TO
INCREASE AFTER 20Z ACROSS PARTS OF THE MID ATLANTIC.

DISCUSSION...RECENT SATELLITE IMAGERY SHOWS INCREASINGLY AGITATED
CUMULUS ALONG AND AHEAD OF A REMNANT OUTFLOW BOUNDARY ACROSS EASTERN
WV AND IN THE VICINITY OF AN EMBEDDED VORTICITY MAXIMA LOCATED IN
NORTHERN WV. THESE FEATURES ARE CO-LOCATED WITH A REGION OF MODEST
WARM AIR ADVECTION ROOTED BETWEEN 925-850 MB. COMBINED, THESE
FEATURES WILL ACT AS THE IMPETUS FOR CONVECTIVE INITIATION ACROSS
NORTHEAST WV AND NORTHERN VA IN THE COMING 1-3 HOURS. 

ALTHOUGH THIS ENVIRONMENT WILL LIKELY FEATURE MODEST INSTABILITY
BETWEEN 500-750 J/KG MLCAPE, 45-50 KNOTS OF EFFECTIVE BULK WIND
SHEAR AND SUSTAINED FORCING FOR ASCENT MAY BE ABLE TO COMPENSATE FOR
THE INSTABILITY AND WILL SUPPORT A HAIL THREAT WITH ANY STRONGER
STORMS. ADDITIONALLY, STEEP BOUNDARY LAYER LAPSE RATES ON THE ORDER
OF 7-8 C/KM ALREADY IN PLACE ACROSS THE REGION (PER SPC
MESOANALYSIS) SUGGESTS THE POTENTIAL FOR STRONG, DOWNDRAFT-DRIVEN
WINDS. DUE TO THESE CONSIDERATIONS, A WATCH MAY BE NEEDED IF
CONFIDENCE INCREASES THAT SUSTAINED ORGANIZED CONVECTION WILL OCCUR.

..MOORE/HART.. 04/07/2020

 

[yoda]

LWX afternoon AFD seems to think 2 more rounds to go... one this evening and one overnight

NEAR TERM /THROUGH TONIGHT/...
Weak frontal zone draped across the area this afternoon with
slightly cooler/drier/more stable air to its northeast across
northern Maryland. Meanwhile, the remnant of a morning
convective cluster in the Ohio Valley is currently crossing
northern parts of the area. Along its southern flank it is
encountering a slightly more unstable airmass and there has been
occasional lightning. This rain, along with dense cloud cover,
will likely reinforce the boundary, keeping the idea that the
best convective activity will remain near or southwest of the
Potomac River through this evening. Additional scattered
showers/storms may for south of this cluster where there has
been more sun. Mid level lapse rates are actually at their
poorest this afternoon, so most activity may tend to struggle to
get going.

An additional convective complex in the upper Ohio Valley may
provide an additional trigger for storms this evening. If steep
low level lapse rates remain, it will make locally damaging
wind gusts the primary threat with any stronger storms. Severe
hail would likely be limited to storms with rotating updrafts
(which is possible due to sufficient shear) with instability
initially rather meager amongst modest surface dew points. This
activity may be assisted as a 700 mb speed max arrives and
instability increases with better lapse rates. However, exact
convective evolution remains quite uncertain through this
evening.

There will likely be a bit of a lull during the late evening,
but then the disturbance and associated low in the upper Great
Lakes will approach late tonight. With a mid and upper speed
max and steep mid level lapse rates associated with this
disturbance, convection will likely be ongoing to our northwest.
While most models are in fairly good agreement with convection
existing, the biggest question is how much of it will survive
through the diurnal minima, though synoptic forcing and
increasing MUCAPE suggest it could. The primary threat with
these storms might be hail (a somewhat uncommon occurrence at
this time of day in this part of the country). The wind threat
with these storms would have to be associated with the strongest
downbursts due to nocturnal stabilization. Any storms that are
left will likely be exiting or dissipating by daybreak

[wawarriors4]

Really good storm moving through just NW of Fredericksburg right now. Heavy Rain, Lightning, Thunder and just had a 44 mph wind gust.

ETA: Severe Thunderstorm Warning just issued

https://twitter.com/NWS_BaltWash/status/1247607555137757184/photo/1

[yoda]

Looks like the sun is trying hard to come back out here

[southmdwatcher]

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.

 

 

[wxdude64]

Well, with the 4th shower/storm of the day here I got to make a hail report to CoCoRaHS, nothing major, 1/4 size, but first hail of the season!

[yoda]

2000 SPC OTLK states that threat for severe hail and wind should increase as diurnal heating continues and references the MCD Eskimo Joe posted above

[NorthArlington101]

https://m.facebook.com/notes/wxriskcom/major-alert-easter-sunday-looks-dangerous/2881339375246635/
Looks like an interesting period of severe WX!

[Kmlwx]

1 minute ago, NorthArlington101 said:

https://m.facebook.com/notes/wxriskcom/major-alert-easter-sunday-looks-dangerous/2881339375246635/
Looks like an interesting period of severe WX!

It looks intense - but primarily for the SE. I'm not convinced we see much of anything up our way other than rain maybe. Bears watching for sure. 

[high risk]

3 minutes ago, Kmlwx said:

It looks intense - but primarily for the SE. I'm not convinced we see much of anything up our way other than rain maybe. Bears watching for sure. 

    I generally agree, but it depends on whether the GFS is right with the secondary low forming near the Carolinas.    That would keep us well in the cool air for sure.   The Euro would at least give us a (small) chance of getting into the warm sector.

[Rhino16]

This is one of those things where you can hear thunder in the distance, but not a single drop of rain...

[Kmlwx]

Just now, high risk said:

    I generally agree, but it depends on whether the GFS is right with the secondary low forming near the Carolinas.    That would keep us well in the cool air for sure.   The Euro would at least give us a (small) chance of getting into the warm sector.

And there's plenty of time to move things around. I'm sure we're not at the final setup on the models. We'll see where we stand later in the week. Would suck if most of us miss out on appreciable storms tonight, tomorrow, Thursday and then the weekend too. 

[high risk]

1 minute ago, Kmlwx said:

And there's plenty of time to move things around. I'm sure we're not at the final setup on the models. We'll see where we stand later in the week. Would suck if most of us miss out on appreciable storms tonight, tomorrow, Thursday and then the weekend too. 

    Well, THAT is depressing.    If this evening and late tonight fail, I still think we have a good shot at a line of storms Thursday, even if limited instability keeps them sub-severe.

[MN Transplant]

The impulse kicking off our next set of storms appears to be in SE Ohio right now.

Had 0.33" earlier with a one rumble of thunder.

[Kmlwx]

21 minutes ago, high risk said:

    Well, THAT is depressing.    If this evening and late tonight fail, I still think we have a good shot at a line of storms Thursday, even if limited instability keeps them sub-severe.

Thunder and gusty winds would be fun. Even if we don't see anything locally for Sunday - just seeing some of the guidance for areas of the Southeast is pretty freaky. 

[Rhino16]

In the Special Weather Statement, I like how they specifically told the people at the hospitals nearby to take shelter, as well as everyone else. They told people at the hospitals to take shelter.

[WxUSAF]

NAM and Hrrr both give me a nice ole.

[Vice-Regent]

Our profile and column is getting trashed by the front-running convection but it is very warm in OH valley. Good for warm air advecting our way to victory.

[yoda]

Big hail core in the supercell in N WV right now

[Sparky]

Just would like to hear thunder and see some lightning in the wee hours tomorrow.

[yoda]

LWX states spotter activation maybe needed overnight in their updated HWO

Also zones have severe wording in them for overnight and tomorrow morning

[osfan24]

Unless I"m missing something, round two for this evening/tonight is looking really bleak on radar.

[yoda]

0100 SPC OTLK mentions MCS complex rolling through overnight with large hail and damaging winds as a threat

MCS development is ongoing across the southern Great Lakes region.
   This large area of storms is forecast to move east-southeastward
   into the Ohio Valley and central Appalachians this evening into
   tonight. A threat for large hail and wind damage will likely exist
   overnight with the stronger thunderstorms within this MCS. An
   isolated wind damage and hail threat may persist through late
   tonight as the MCS moves into the Mid-Atlantic region.

[yoda]

STWatch issued until 3AM for where the MCS is developing back in OH and MI - https://www.spc.noaa.gov/products/watch/ww0084.html

[high risk]

34 minutes ago, yoda said:

0100 SPC OTLK mentions MCS complex rolling through overnight with large hail and damaging winds as a threat

 

 

       It's still on the table for sure.     I was super optimistic about this threat in my  morning posts, but my enthusiasm has been tempered by multiple CAMs showing the section of the MCS in the DC-Baltimore corridor falling apart just before it arrives, while the sections further east and west persist.     Still, some of the solutions have at least some of the system surviving into the metro areas, and the lapse rates aloft are still progged to be terrific, so I'm not ruling out storms with hail very late tonight.

[yoda]

15 minutes ago, high risk said:

       It's still on the table for sure.     I was super optimistic about this threat in my  morning posts, but my enthusiasm has been tempered by multiple CAMs showing the section of the MCS in the DC-Baltimore corridor falling apart just before it arrives, while the sections further east and west persist.     Still, some of the solutions have at least some of the system surviving into the metro areas, and the lapse rates aloft are still progged to be terrific, so I'm not ruling out storms with hail very late tonight.

LWX evening AFD update agrees with you

NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Other than the single weakening supercell over far western
Virginia, showers and thunderstorms have mostly waned due to the
stable atmosphere provided across the region in the wake of the
earlier convection. Another disturbance and associated low in
the upper Great Lakes will approach late tonight. With a mid and
upper speed max and steep mid level lapse rates associated with
this disturbance, convection is currently ongoing to our
northwest. While most models are in fairly good agreement with
convection existing, the biggest question is how much of it will
survive through the diurnal minima, though synoptic forcing and
increasing MUCAPE suggest it could. The primary threat with
these storms might be hail (a somewhat uncommon occurrence at
this time of day in this part of the country). The wind threat
with these storms would have to be associated with the strongest
downbursts due to nocturnal stabilization. Any storms that are
left will likely be exiting or dissipating by daybreak.

[high risk]

00z NAM nest also does the split with the late night MCS around the metro areas, but on the plus side, it looks WAY better for Thursday.    The midday line has 2000 j/kg of sfc-based cape to work with and healthy deep layer shear.     This is the first cycle to show that good instability, so will need to see it maintain that signal.

[yoda]

Wow... impressive

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1140 PM EDT TUE APR 07 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1019 PM     HAIL             SPOTTSWOOD              37.95N  79.21W
04/07/2020  E1.00 INCH       AUGUSTA            VA   911 CALL CENTER

            HAIL ACCUMULATING 2 INCHES DEEP ON I-81 NEAR SPOTSWOOD
            CAUSED MULTIPLE ACCIDENTS AND PARTIALLY CLOSED THE
            HIGHWAY


&&

EVENT NUMBER LWX2000890

[yoda]

https://www.spc.noaa.gov/products/md/md0304.html

Mesoscale Discussion 0304
   NWS Storm Prediction Center Norman OK
   1252 AM CDT Wed Apr 08 2020

   Areas affected...Portions of southeastern OH...northern
   WV...southwestern PA...western MD...and far northern VA

   Concerning...Severe Thunderstorm Watch 85...

   Valid 080552Z - 080715Z

   The severe weather threat for Severe Thunderstorm Watch 85
   continues.

   SUMMARY...A line of strong to severe storms capable of producing
   mainly damaging winds will continue east-southeastward. Downstream
   watch issuance is possible.

   DISCUSSION...Storms have grown upscale across parts of southeastern
   OH into western PA, with mainly severe/damaging winds being
   reported, including a gust to 75 mph at the Pittsburgh International
   Airport. The airmass downstream of this ongoing convection is not
   particularly unstable given cooler low-level temperatures and less
   low-level moisture. With MUCAPE generally 500-1000 J/kg, storms may
   have a tendency to become slightly elevated with time, particularly
   with eastward extent. Still, given the well-organized nature of the
   line and strong outbound velocities noted on KPBZ radar, there
   appears to be a continued strong to damaging wind threat that may
   extend to the south/southeast of ongoing Severe Thunderstorm Watch
   85. Accordingly, another watch may be needed across parts of
   southwestern PA into western MD and the eastern WV Panhandle.

   ..Gleason/Thompson.. 04/08/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...CTP...LWX...PBZ...RLX...

[yoda]

5 hours ago, high risk said:

00z NAM nest also does the split with the late night MCS around the metro areas, but on the plus side, it looks WAY better for Thursday.    The midday line has 2000 j/kg of sfc-based cape to work with and healthy deep layer shear.     This is the first cycle to show that good instability, so will need to see it maintain that signal.

New day 2 from SPC was quite meh unfortunately