2019 Mid-Atlantic Severe Wx - General Discussion

[high risk]

18 minutes ago, yoda said:

Its too bad we have next to zero MLCAPE/instability... shear is excellent and low level shear is silly good

No doubts at all about the shear.     NAM nest showed a strongly forced line of convection moving through very early Sunday.     As Yoda notes, instability is pretty meager, but temps will be rising through the 60s Saturday night, so being able to mix down some momentum to the sfc isn't a total fantasy.

[yoda]

11 minutes ago, high risk said:

No doubts at all about the shear.     NAM nest showed a strongly forced line of convection moving through very early Sunday.     As Yoda notes, instability is pretty meager, but temps will be rising through the 60s Saturday night, so being able to mix down some momentum to the sfc isn't a total fantasy.

Indeed... 12z NAM was showing 850mb winds of 60 to 70 kts

[yoda]

Saturday night ideas from LWX afternoon AFD:

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
Atypical warmth will build across the Mid Atlantic this weekend.
The forecast area will remain east of the approaching cold front
and trough axis Saturday, permitting a plume of warm/moist air
(H8 temps 10-14C/surface dewpoints 55-60F) to overspread the
region. Have bumped the MaxT forecast up to 65-70F based on this
thermal advection, in spite of limited insolation. Precip
chances will slowly spread east through the day as heights
lower. The catalyst will still be isentropic in nature, and will
be characterizing this as rain.

The forecast becomes interesting Saturday night as the frontal
boundary crosses the region...most likely late evening through
the overnight hours. While model soundings overall still remain
mostly stable, a plume of MUCAPE in the neighborhood of 200-300
J/kg rides north ahead of the frontal boundary. (Some HREF
member soundings are conditionally unstable.) Shear is not
lacking-- 50-60 kt between 0-3 km and tail end of 70-80 kt in
the 0-6km layer. Precipitable water also exceptionally high for
the season. And, there is plenty of lift from both isentropic
upglide as well as frontal convergence. This forcing might be
able to overcome the overall sounding profile, climatology, and
the diurnal cycle to produce locally strong wind gusts, mainly
coincident with a 70 kt low level jet along/ahead of the cold
front. Hence, most of the forecast area has been added to a
Marginal Risk of severe weather late Saturday night.

In the database, have increased wind gusts slightly...not to
severe or Wind Advisory levels, but enough to hopefully get some
wind gusts into the forecast. In addition, have also added a
slight chance of thunder. Its plausible that strong wind gusts
may be able to develop without lightning/thunder, so do not wish
to ramp that element up higher. Have also bumped up lows to the
mid 50s-lower 60s, with dewpoints almost matching.

[Kmlwx]

A little early for me to make my annual thread - I"ll wait at least another few weeks

[yoda]

2% TOR makes it up to EZF on the 2000 SPC OTLK for late tonight

[Kmlwx]

Assuming the most we'll get is a gusty shower. First meh of 2020 from me. 

[yoda]

2 hours ago, Kmlwx said:

Assuming the most we'll get is a gusty shower. First meh of 2020 from me. 

SLGT gets extended to EZF... 2% TOR gets into DCA 

[yoda]

2 hours ago, Kmlwx said:

Assuming the most we'll get is a gusty shower. First meh of 2020 from me. 

Watch possible per latest MCD

[Kmlwx]

5 minutes ago, yoda said:

Watch possible per latest MCD

Not for me. lol

[yoda]

First catch of the season 

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Baltimore MD/Washington DC
1143 PM EST Sat Jan 11 2020

The National Weather Service in Sterling Virginia has issued a

* Severe Thunderstorm Warning for...
  Southeastern Madison County in northwestern Virginia...
  Orange County in central Virginia...
  Southeastern Fauquier County in northern Virginia...
  Culpeper County in northern Virginia...
  Western Spotsylvania County in central Virginia...

* Until 1230 AM EST.

* At 1143 PM EST, severe thunderstorms were located along a line
  extending from 6 miles north of Culpeper to near Orange to 8 miles
  northwest of Boswells Tavern, moving east at 45 mph.

  HAZARD...60 mph wind gusts.

  SOURCE...Radar indicated.

  IMPACT...Damaging winds will cause some trees and large branches
           to fall. This could injure those outdoors, as well as
           damage homes and vehicles. Roadways may become blocked by
           downed trees. Localized power outages are possible.
           Unsecured light objects may become projectiles.

* Locations impacted include...
  Culpeper, Orange, Bealeton, Gordonsville, Opal, Remington, Catlett,
  Calverton, Midland, Brandy Station, Barboursville, Verdiersville,
  Casanova, Montpelier Station, Locust Grove, Thornhill, Winston,
  Madison Mills, Montford and Cardova.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

[yoda]

Rotation marker in the line near Reston

[87storms]

4 hours ago, Kmlwx said:

Assuming the most we'll get is a gusty shower. First meh of 2020 from me. 

It’ll be gusty showers, but wouldn’t be surprised to see local torrents. Bonus for thunder, but I gotta think that’s unlikely. 

[yoda]

2 more STWs issued by LWX tonight