2025 Severe Weather General Discussion

[high risk]

11 hours ago, Kmlwx said:

One thing to note - the GFS seems to be much faster than the Euro.

      GFS has a known progressive bias.

[yoda]

Mention of tornado and supercells in this morning's AFD from LWX 

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
By Wednesday morning, a strong, occluded surface low will have
tracked to near Chicago, with an accompanying deep upper
trough/closed mid-level low occupying much of the eastern half of
the CONUS. As large scale ascent downstream of the approaching upper
trough starts to overspread the area, a strong low-level jet (around
60-80 knots at 850 hPa) will move in from the southwest. Warm
advection driven precipitation associated with this strong low-level
jet should move across the area from southwest to northeast during
the morning to early afternoon hours. Model soundings within this
warm advection regime show a deep moist neutral to slightly stable
profile, with very long, curved hodographs. This would likely result
in a period of stratiform rain, but a narrow convective line that`s
strongly forced on the synoptic scale (by differential cyclonic
vorticity advection driven ascent) can`t be ruled out on the back
edge of the precipitation shield. If such a line were to
materialize, it could pose a threat for strong to severe wind gusts,
and possibly even a QLCS tornado. As the stronger low-level jet and
associated warm advection depart off to our north and east during
the afternoon, we should break out into the warm sector while a mid-
level dry slot simultaneously works in aloft. This should enable
daytime heating and development of some surface based instability
from southwest to northeast during the late morning to afternoon
hours. Within the dry slot, model soundings show straight, but very
long hodographs, with ample deep layer shear available to any storms
that form. Large scale forcing for ascent will be lesser both at low-
levels (with the loss of warm advection) and aloft (with the
strongest DCVA driven ascent departing off toward the east.

The combination of surface heating and gradual height falls aloft may
be enough for some additional showers or thunderstorms to form during
the afternoon. Storms could also potentially form along the system`s
surface cold front, but various models differ on the timing of the
cold frontal passage, with some guidance (such as the GFS) moving
the front into western portions of the forecast area prior to
sunset, while others (such as the Euro and Canadian) hold the
frontal passage off until after dark. If storms were to form during
the afternoon within the dry slot, supercells primarily capable of
producing damaging winds and hail could be possible. As of yesterday
morning, SPC highlighted much of the forecast area in a rare day 5
Slight Risk to account for the potential of severe thunderstorms.

With ongoing drought across much of the area and very dry conditions
over the past week, rainfall with this system looks like it will be
largely beneficial in nature, with most guidance showing around a
half of an inch to an inch of precipitation. Outside of any
thunderstorms, winds will be gusty out of the south, with high
temperatures generally in the 60s.

[yoda]

All 3 zone issued HWOs from LWX (issued at 411pm) now mention tornado chances for Wednesday 

DAYS TWO THROUGH SEVEN...Monday through Saturday

Isolated severe thunderstorms capable of producing damaging wind
gusts are possible on Wednesday. A tornado or two cannot be ruled
out as well.

Strong west to northwest winds, including gale conditions, are
possible on Thursday behind a strong cold front.

[yoda]

SPC day 3 morning outlook makes it sound if there is two distinct threat periods on Wednesday - morning and then late afternoon 

[yoda]

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0215 AM CST Mon Mar 03 2025

   Valid 051200Z - 061200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WEDNESDAY ACROSS
   THE MID ATLANTIC...

   ...SUMMARY...
   Severe thunderstorms capable of producing damaging winds and a few
   tornadoes are possible across parts of the southern and middle
   Atlantic Seaboard on Wednesday.

   ...Discussion...
   Models continue to indicate that the center of a broad and deep,
   occluding surface cyclone will migrate from the Upper Midwest
   through the lower Great Lakes region into Quebec during this period.
    Associated strong lower/mid-tropospheric wind fields are likely to
   impact a broad area east of the Rockies through the Atlantic
   Seaboard.  Models indicate that this may include, south to
   southwesterly flow on the order of 50-90+ kt within a moistening
   warm sector, east of deepening surface troughing to the lee of the
   Blue Ridge, and perhaps ahead of an eastward surging cold front
   across parts of the Allegheny Plateau into lower Great Lakes
   vicinity.

   Although more favorable low-level moisture return from the Gulf may
   become cut off by early Wednesday, moistening may be augmented
   somewhat by a developing return flow off a modifying boundary-layer
   offshore of the southern Atlantic Seaboard.  Models still indicate
   that this may only become supportive of weak destabilization. 
   However, given the strength of the wind fields and areas of stronger
   forcing for ascent, there appears at least a conditional risk for
   severe thunderstorm activity across a broad area.

   ...Southern through Mid Atlantic...
   Models indicate that surface dew points may increase into the 60s F
   in a corridor across the Carolinas through Virginia during the day.
   Latest NAM forecast soundings suggest that this might occur across
   parts of the Carolina Piedmont into coastal plain prior to the
   arrival of a remnant convective band emerging from the eastern Gulf
   States.  Although lower/mid-tropospheric lapse rates are forecast to
   be rather weak, weak near-surface destabilization might become
   sufficient to support a risk for tornadoes and/or damaging straight
   line wind gusts, given forecast very large, clockwise curved
   low-level hodographs.

   In the wake of this initial band of convection, beneath a developing
   dry slot, northward moisture advection and insolation to the lee of
   the Blue Ridge may contribute to modest destabilization by late
   Wednesday afternoon.  It appears that this will be aided by the
   leading edge of stronger mid-level cooling spreading to the east of
   the Appalachians, and accompanied by increasing thunderstorm
   development in the presence of strong deep-layer shear.  Although
   forecast soundings suggest that low-level hodographs may become more
   modest by this time as the stronger low-level jet core spreads
   offshore, the environment may still become conducive to supercells
   with potential to produce severe wind, hail and perhaps a tornado.

   ..Kerr.. 03/03/2025

[high risk]

54 minutes ago, yoda said:

SPC day 3 morning outlook makes it sound if there is two distinct threat periods on Wednesday - morning and then late afternoon 

Right now, the morning threat appears to be south of the DC area.   While the wind fields will be terrific, there likely  won’t be sufficient time to advect the unstable air mass far enough north.    For now, I agree with SPC that the best opportunity in our area is with the evening front.  The wind fields will be weaker, and surface winds may start to veer a bit, but a wind threat will exist if we can get a bit of instability. 

[Eskimo Joe]

12z NAM never gets dewpoint temps above 60F north of the Virginia Tidewater. Not sure why we have a D3 slight risk this far north.

[dailylurker]

18 minutes ago, Eskimo Joe said:

12z NAM never gets dewpoint temps above 60F north of the Virginia Tidewater. Not sure why we have a D3 slight risk this far north.

I've always ignored severe weather forecast. This area doesn't do severe very often, especially in March. What I'm usually interested in is rain and how much. 

[Kmlwx]

13 minutes ago, dailylurker said:

I've always ignored severe weather forecast. This area doesn't do severe very often, especially in March. What I'm usually interested in is rain and how much. 

This *may* be a setup where we don't need ample dews with how dynamic the system is. It's rare (like you said) but we've certainly had a few Feb/Mar systems do some pretty impressive things. I like to think of our severe events as "balancing acts." Too little of any factor and yeah you will fail - but this is one of the times of year that lack of raw instability CAN be made up for with wind fields and such. 

Again - not saying that this will be the case - I'd put bets on this just being a gusty lines of showers with an embedded rumble of thunder...but stranger things have happened. 

[Stormchaserchuck1]

1 hour ago, Eskimo Joe said:

12z NAM never gets dewpoint temps above 60F north of the Virginia Tidewater. Not sure why we have a D3 slight risk this far north.

The low is projected to be 978-979mb in Missouri and Illinois.. maybe they think it will overperform north.  I think it's a little too cold up this way for severe wx. 

[yoda]

Afternoon AFD from LWX on the severe threat

An active weather day lies ahead on Wednesday with areas along
and east of the Blue Ridge in a Day 3 Slight Risk for severe
thunderstorms. The 12Z high-resolution model suite shows two
possible rounds of convection. What remains of a line of severe
thunderstorms tracking across the Tennessee Valley on Tuesday
night will overspread the local area late Wednesday morning into
the afternoon. Anticipate the Mid-Atlantic region being heavily
clouded over which would limit the available instability.

Heading into the remainder of the afternoon hours, temperatures
should push into the low/mid 60s, with mainly 50s over mountain
locales. Models show a dry slot pushing through the area which
may allow for some breaks in the cloud cover. As this occurs,
the 0-6 km vertical shear increases to some rather extreme
values of 85 to 95 knots. Given enough residual buoyancy in the
atmosphere, a discernible risk of severe weather would occur.
However, as usual, a number of factors have to be ironed out in
the next day. For now, prepare for a potential of damaging wind
gusts, along with a tornado or two.