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.

 

[high risk]

8 hours 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.

Uh, because guidance shows actual sfc-based instability this far north…..

[high risk]

Looking at the 00Z guidance, the timing for Wednesday now appears slower which probably reduces the severe threat for those of us in central MD.     Some thoughts:

    1)   Several CAMs show an intense, forced line of convection sweeping through during the midday hours.   Wind fields are intense, but there just isn't any instability until you get south of Richmond, and it's pretty meager down there too.   If there is a severe threat with this feature, it's likely well south and southeast of the DC area.

   2)   As the dry slot approaches and much colder air aloft overspreads the area, convection is likely to form later in the day over western VA and move eastward.    Wind fields are weaker but still sufficient for a severe threat, and there may be just enough sfc-based instability for a low-end wind threat and perhaps some hail too. What's not as good is that the timing of the system reduces the instability, especially for areas on the east side of the Potomac.    There is still some severe threat, but it's highest over northern VA.

[yoda]

SLGT risk for everyone on new Day 2 morning update... 2/15/15

ENH introduced in SE VA into the Carolinas 

[yoda]

 

 

 

 

[yoda]

Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1214 AM CST Tue Mar 04 2025

   Valid 051200Z - 061200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS WEDNESDAY
   ACROSS PARTS OF EASTERN SOUTH CAROLINA...EASTERN NORTH CAROLINA AND
   SOUTHEASTERN VIRGINIA...

   ...SUMMARY...
   An intensifying line of thunderstorms may become capable of
   producing strong, damaging wind gusts and a few tornadoes as it
   overspreads the eastern Carolinas and southeastern Virginia mid
   Wednesday morning through Wednesday afternoon.

   ...Discussion...
   The center of a broad and deep, occluding surface cyclone still
   appears likely to migrate across the lower Great Lakes region into
   southwestern 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, initially
   including south-southwesterly flow on the order of 50-70+ kt around
   850 mb,  east of deepening surface troughing to the lee of the Blue
   Ridge. It appears that this jet core will gradually shift eastward
   into and across the Mid Atlantic coast by late afternoon, well in
   advance of the primary cold front, which might not advance east of
   the Appalachians until Wednesday evening.

   Guidance continues to indicate that more the substantive low-level
   moisture return off a modifying Gulf boundary layer will become cut
   off across the northeastern Gulf vicinity by early Wednesday. 
   However, it remains suggestive that a developing return flow off the
   Atlantic will augment moistening across and inland the Carolina
   coast.

   Models also continue to indicate that destabilization through much
   of the warm sector may only become supportive of weak CAPE on the
   order of 500 J/kg or less.  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 Mid Atlantic...
   It still appears that a remnant convective band emerging from the
   eastern Gulf States will be maintained, with potential for
   substantive intensification as it advances across the Carolina
   Piedmont through Carolina and southeastern Virginia coastal plain
   Wednesday morning into afternoon.  Although forecast soundings
   continue to indicate that lower/mid-tropospheric lapse rates will
   not become particularly steep ahead of this convection, it does
   appear that boundary-layer warming and moistening (including surface
   dew points increasing into the lower 60s) will contribute to
   near-surface thermodynamic profiles conducive to downward momentum
   transport.  Given the rather large and clockwise curved low-level
   hodographs, a few tornadoes (perhaps a strong tornado or two) are
   possible, in additional to scattered straight-line wind gusts in
   excess of 65 kt.

   ...Allegheny Plateau/Mid Atlantic...
   Early period convective precipitation may contribute to
   boundary-layer moistening, prior to the onset of increasing
   insolation beneath a dry slot overspreading the region during the
   day.  Followed by the onset of stronger cooling aloft, model
   forecast soundings indicate the development of thermodynamic
   profiles characterized by modest conditional and convective
   instability, in the presence of strong deep-layer shear.  Guidance
   has been varied concerning the location and extent of scattered
   pre-frontal thunderstorm development within this regime, but the
   environment is likely to become at least marginally conducive to
   scattered organized convection, including supercells.

   ..Kerr.. 03/04/2025

[Kmlwx]

At least we've "got" the 0z FV3 lol

[Kmlwx]

Actually...the ARW, ARW2, and HRDPS all have a similar line with similar northern extent. BRING ME MY GUSTY SHOWERS! 

[yoda]

LWX AFD from this morning on the dual threat tomorrow 

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Come tomorrow, attention will turn to a very potent storm system
approaching the area from the west. As of early this morning,
low pressure is in the process of rapidly deepening over the
Central Plains. This area of low pressure will track
northeastward toward the Great Lakes tonight into tomorrow,
while eventually deepening into the lower 980s hPa. A powerful
upper level trough will accompany this system, with a large
closed low developing in the mid-levels. Winds will be very
strong through the depth of the troposphere in association with
this system, with a low-level jet at 850 hPa strengthening to
around 60-80 knots.

A band of showers and thunderstorms is in the process of
developing now over the Southern Plains. This area of showers
and thunderstorms occurring coincidentally with the strong warm
advection in association with the core of the low-level jet
will race eastward across the southern US today, eventually
approaching the area from the southwest later tonight. This
activity is expected to weaken into primarily stratiform
precipitation by daybreak tomorrow as it starts to move into
southwestern portions of the forecast area. As this area of
precipitation coincident with the core of the low-level
jet/strong warm advection at low-levels progresses east of the
mountains tomorrow morning, it will encounter an airmass with
slightly higher dewpoints, which may lead to reinvigoration of
the convective line late tomorrow morning into early tomorrow
afternoon as it moves across the area from southwest to
northeast. Surface based instability appears to be minimal (100
J/kg or less), if existent at all, but most CAMs show an
impressive squall line developing toward the back edge of the
precipitation shield as very strong synoptic scale ascent ahead
of the approaching upper trough arrives. As this occurs, a very
strong wind field will be in place, with 60-70 knots at 850
hPa. Model soundings show very long, curved hodographs, with
ample SRH. Such an environment raises concerns that damaging
winds and potentially even a QLCS tornado or two may possible as
the convective line moves through the region. SPC currently has
us outlooked with a Slight Risk for severe thunderstorms to
account for this potential.

The aforementioned band of showers and thunderstorms will exit
off toward the north and east along with the core of the LLJ by
mid-afternoon, with a mid-level dry slot overspreading most of
the area from southwest to northeast. Additional surface heating
will occur within this mid-level dry slot as clouds clear out,
resulting in the development of surface based instability within
a still highly sheared environment. With the best synoptic scale
ascent moving off to our north and east, questions remain
regarding how much development of additional showers and
thunderstorms will occur behind the first round of showers and
storms. However, if storms were to occur, they`d potentially be
supercellular in nature (given very long, straight hodographs),
and capable of producing both damaging winds and hail. It
currently appears as though western portions of the forecast
area would have the best chance of seeing storms with the second
round later tomorrow afternoon into tomorrow evening, as
they`ll clear out first and have the longest duration of surface
heating. They`ll also have greater forcing at low-levels as a
pre-frontal trough, and eventually the surface cold front move
in from the west late tomorrow afternoon into tomorrow evening.

[Kmlwx]

Even if sub-severe this looks like good tracking practice for spring!  

 

[Kmlwx]

In all seriousness - I still continue to expect nothing more up here than gusty showers. It's worth noting,  however, that some of the NSSL models (experimental?) bring better parameters into parts of the closer-in metro areas tomorrow in the 17z-20z timeframe. While I concur with SPC (of course) that the best threat is well south of us like SEVA and into NC...I've continually been saying that dynamic systems can surprise. 

The 1730z Day 2 Outlook from SPC even mentions "strong tornado" potential in the enhanced area! While nothing like that will be realized this far north - my eyes will be on subsequent 3km NAM runs and the HRRR even once it's more in range. For now, the NAM and NAM nest are a lot less enthused than some of the B-team models like the ARW and NSSL models. I haven't tracked the verification scores on those NSSL models either...so it could be that they all more or less follow the leader. 

Even the robust models quickly wind down the threat NE of the Potomac - but counties adjacent continue to be worth monitoring. 

The image I posted above if it were 70s-80s degrees and moist would scream "line of supercells" to me...but think things might be overdone on that. 

[Eskimo Joe]

39 minutes ago, Kmlwx said:

In all seriousness - I still continue to expect nothing more up here than gusty showers. It's worth noting,  however, that some of the NSSL models (experimental?) bring better parameters into parts of the closer-in metro areas tomorrow in the 17z-20z timeframe. While I concur with SPC (of course) that the best threat is well south of us like SEVA and into NC...I've continually been saying that dynamic systems can surprise. 

The 1730z Day 2 Outlook from SPC even mentions "strong tornado" potential in the enhanced area! While nothing like that will be realized this far north - my eyes will be on subsequent 3km NAM runs and the HRRR even once it's more in range. For now, the NAM and NAM nest are a lot less enthused than some of the B-team models like the ARW and NSSL models. I haven't tracked the verification scores on those NSSL models either...so it could be that they all more or less follow the leader. 

Even the robust models quickly wind down the threat NE of the Potomac - but counties adjacent continue to be worth monitoring. 

The image I posted above if it were 70s-80s degrees and moist would scream "line of supercells" to me...but think things might be overdone on that. 

Don't sleep on setups like this. We had a marginal risk for severe weather in February just before covid kicked off that yielded numerous wind reports and several tornadoes after just an hour or two of sun:

https://www.spc.noaa.gov/exper/archive/event.php?date=20200207

[Stormchaserchuck1]

The northern, marginal, part of the storm threat today isn't happening so far.. they are more south. Don't know if that carries into tomorrow, temps are a little bit warmer today in the east than projected. 

[Hank Scorpio]

1 hour ago, Eskimo Joe said:

Don't sleep on setups like this. We had a marginal risk for severe weather in February just before covid kicked off that yielded numerous wind reports and several tornadoes after just an hour or two of sun:

https://www.spc.noaa.gov/exper/archive/event.php?date=20200207

Lots of damage photos on X from that day:

https://x.com/search?q=Leesburg tornado until%3A2020-02-10 since%3A2020-02-07&src=typed_query

[midatlanticweather]

1 hour ago, Hank Scorpio said:

Lots of damage photos on X from that day:

https://x.com/search?q=Leesburg tornado until%3A2020-02-10 since%3A2020-02-07&src=typed_query

I was in the drive-thru at McDonald's when that thing ripped through! I was shocked by the heaviness of the rain and the winds. I thought that if it were summer, I would wonder if a tornado or downburst hit. I traveled in the opposite direction from where the tornado touched down but was not surprised when I learned one had hit. 

[wasnow215]

18z models looked way more interesting for tomorrow. 

[StormyClearweather]

I don't hate this look. 

3K NAM has it pushing through a couple of hours later. 

[SnowenOutThere]

30 minutes ago, wasnow215 said:

18z models looked way more interesting for tomorrow. 

0z 3k Nam looks even more intense

[high risk]

Pretty remarkable CAM agreement on an intense line rolling through the area in the early afternoon tomorrow.   (The NAM Nest is a bit later than any other guidance, but it has a notorious slow bias on convective timing.)   The reflectivities look amazing, but is there really any severe potential with it in the DC area?    The wind fields are amazing, and if we had even 500 j/kg of sfc-based cape, we'd be looking at widespread damaging winds and QLCS tornadoes.    But there really isn't any instability shown by any model.  Maybe the HRRR squeezes out 50-100 j/kg, but it looks warmer than most other guidance.     So, I have to wonder if this will be just  a short period of torrential rain followed by stratiform.    Before I totally poo-poo the threat, however, it's worth noting that sometimes the incredible shear and overall dynamics can drive severe weather with a forced line in an environment with basically no cape, so I won't rule out a damaging event with an isolated brief pinup, but I don't think that it's likely.

The better environment actually establishes itself over northern VA and areas to the north and northwest in the evening hours, as the very cold air aloft arrives, steeping lapse rates.    Go look at sfc-based cape fields for the early evening hours.   The values aren't awesome, but they're notably higher than during the early afternoon event.    Wind fields are still decent, so any cells would likely be supercellular have hail and wind potential.    Unfortunately, the upper system arrives just a bit too late, and nighttime sfc cooling with reduce the potential as the evening goes on.    The best severe threat with this round will be over eastern WV, northwestern VA, and up into PA.   Maybe an isolated cell can pop across the DC metro area, and it would have severe potential if it did, but the threat appears low there at this time.