2025 Severe Weather General Discussion

[yoda]

8 hours ago, high risk said:

Oh, what the hell!    Let's fire up the SVR thread for perhaps its last hurrah of 2025.  MRGL for tomorrow - the shear/instability combo isn't great, but I could see a few decent wind gusts.   Will be very happy with thunder and heavy rain.   The CAMs today mostly favored DC and points south, but the HRRR has kicked off the evening suite by favoring generally north of DC.

3 straight days of MRGL per SPC... today through Thursday 

[yoda]

Chance of maybe an isolated spinner today?  Morning AFD from LWX 

The first wave of showers and thunderstorms look to exit mid to late
morning allowing the atmosphere to reload for the afternoon and
evening ahead. Some uncertainty remains into how much clearing that
we do see given the morning activity and incumbent trough/surface
cold front nearby. Even with that said, the added lifting mechanism
of the trough/front and leading shortwave energy should aid in
higher convective chances this afternoon. The Storm Prediction
Center has a Marginal Risk (Level 1 out of 5) for severe weather
today east of the Allegheny Mountains. The main threat is damaging
winds and heavy rainfall with a secondary threat of an isolated
tornado. CAPE values look to sit between 1000-2000 j/kg with deep
layer shear around 40 to 50 kts. This should lead to some
organization if storms are to materialize (i.e line segments or even
a supercell or two). The NAM3km/NSSL/ARW remain the aggressors when
it comes to curved hodographs with 0-1 SRH values up around 200-250
m2/s2. The RAP/HRRR show less values and less of a curved signature.
With that said, the tornado threat would remain isolated (i.e via
supercell or most likely in a QLCS type of scenario) with a focus
east of US-15. Greatest concern for severe weather if it were to
occur would be between 4-8pm as the front crosses. Once again the
threat will be highly dependent upon cloud cover and how quickly
things can reload after this morning`s rainfall. Afternoon high`s
will reach into the upper 70s and low 80s (upper 60s and low 70s
mountains).

[high risk]

Tough to do severe here (from non-TC events) in mid October, but Sunday evening has some potential, especially if we look at the ECMWF solution of a deepening surface low over western PA.  Instability is always a limiting factor at this time of year, and the timing of the system isn’t perfect, but it’s a strong trough with good wind fields.  

[George BM]

2 hours ago, high risk said:

Tough to do severe here (from non-TC events) in mid October, but Sunday evening has some potential, especially if we look at the ECMWF solution of a deepening surface low over western PA.  Instability is always a limiting factor at this time of year, and the timing of the system isn’t perfect, but it’s a strong trough with good wind fields.  

Schumacher actually has much of the area in 15% for Sunday.

https://schumacher.atmos.colostate.edu/hilla/csu_mlp/csu_severe.php?date=20251016&version=2021&day=4&product=severe_ml_day4_gefso&day_str=1020&init=00

[yoda]

2 hours ago, high risk said:

Tough to do severe here (from non-TC events) in mid October, but Sunday evening has some potential, especially if we look at the ECMWF solution of a deepening surface low over western PA.  Instability is always a limiting factor at this time of year, and the timing of the system isn’t perfect, but it’s a strong trough with good wind fields.  

SPC is monitoring 

Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0347 AM CDT Thu Oct 16 2025

   Valid 191200Z - 241200Z

   ...DISCUSSION...
   ...Sunday/Day 4 and Monday/Day 5...
   A large-scale mid-level trough and an associated cold front are
   forecast to move through the Ohio and Tennessee Valleys on Sunday.
   Thunderstorms will likely be ongoing across the central Gulf Coast
   states and Tennessee Valley at the start of the period. This
   convection should have a negative impact on instability across the
   much of the moist sector during the day. In areas that are not
   impacted, weak instability is forecast to develop ahead of the front
   from Georgia and the Carolinas into the central Appalachians. The
   instability combined with strong large-scale ascent and moderate to
   strong deep-layer shear will likely result in a severe threat. A
   potential for wind damage and a few tornadoes will be possible. At
   this time, uncertainty is substantial as to exactly where the
   greatest severe potential will occur. As new runs come in, an
   upgrade to Slight may be needed.

   A mid-level low is forecast to move across the Northeast on Monday,
   as the associated trough moves into the western Atlantic.
   Thunderstorms with an isolated severe threat will be possible in
   parts of southern New England during the late morning and early
   afternoon before the front moves offshore.

[wxmeddler]

This is one heck of a front, dynamics look great, just need moisture.

[Kmlwx]

7 hours ago, wxmeddler said:

This is one heck of a front, dynamics look great, just need moisture.

It's really one of those times when I might be "in" just purely based on the dynamics. Even without moisture it has the feels of one of those very gust shower lines...and more upside potentially. 

I think there was a really potent storm system in like November 2006 that did some fun stuff around these parts

[Kmlwx]

1 minute ago, Kmlwx said:

It's really one of those times when I might be "in" just purely based on the dynamics. Even without moisture it has the feels of one of those very gust shower lines...and more upside potentially. 

I think there was a really potent storm system in like November 2006 that did some fun stuff around these parts

Found this screen cap I took. It was Nov 16, 2006. Haven't looked at H5 yet so it may not even be a close match - but anecdotally that's my high water level for Oct/Nov severe potential. 

[George BM]

41 minutes ago, Kmlwx said:

Found this screen cap I took. It was Nov 16, 2006. Haven't looked at H5 yet so it may not even be a close match - but anecdotally that's my high water level for Oct/Nov severe potential. 

I remember this day very well. One of a few times during my grade-school years when there was a thunderstorm during school hours (5th grade). The good stuff was to my east but there was heavy rain and occasional lightning and it was really dark blue outside.

[Kmlwx]

1 hour ago, George BM said:

I remember this day very well. One of a few times during my grade-school years when there was a thunderstorm during school hours (5th grade). The good stuff was to my east but there was heavy rain and occasional lightning and it was really dark blue outside.

Here's the LWX disco from that day 

 

.MESOSCALE...
 WATER VAPOR LOOP EARLY THIS MORNING PLACES A STRONG UPPER LOW ACROSS 
 THE TENNESSEE VALLEY...MOVING TO THE NORTHEAST. A PRONOUNCED DRY 
 SLOT IS PENETRATING WEST VIRGINIA AND SOUTHWEST VIRGINIA FROM THE 
 WEST. 13Z SURFACE MESOANALYSIS PLACES A 993MB OCCLUDED CYCLONE IN 
 SOUTHERN INDIANA...WITH THE OCCLUDED/COLD FRONT CUTTING THROUGH 
 CENTRAL WEST VIRGINIA SOUTHEAST THROUGH THE CENTRAL CAROLINAS. A 
 WARM FRONT IS PUNCHING NORTH INTO CENTRAL VIRGINIA...STALLING IN THE 
 VICINITY OF THE WEST COAST OF THE CHESAPEAKE BAY.
 
 RUC MODEL INDICATES TONGUE OF RICH PRECIPITABLE WATER VALUES IS 
 MOVING NORTH ALONG THE BLUE RIDGE (INCREASING FROM 12Z RAOB VALUES 
 OF 1.3" TO 1.7"). MEANWHILE...DRY SLOT ALOFT IS OVERRUNNING RICH 
 BOUNDARY LAYER MOISTURE...WHICH SHOULD INCREASE INSTABILITY AND 
 CONVECTIVE UPDRAFT STRENGTH. GIVEN RICH PRECIPITABLE WATER VALUES 
 AND DEWPOINTS JUST BEHIND THE OCCLUDED/COLD FRONT...CURRENT THINKING 
 IS STRONG CONVECTIVE LINE WILL DEVELOP ALONG THE BOUNDARY WEST OF 
 CURRENT PRECIPITATION. ROTATING STORMS WILL BE POSSIBLE IN SOUTH TO 
 NORTH LINE SEGMENTS AHEAD OF THE COLD FRONT.
 
 SHEAR INDICES ARE QUITE HIGH TODAY. WIND PROFILES OBSERVED ON KLWX 
 WIND PROFILE INDICATE SOUTHEAST WINDS 25 KNOTS AT 1KFT...INCREASING 
 TO 60 KNOTS FROM THE SOUTH AT 3KFT. 06Z GFS BUFKIT FORECAST 
 SOUNDINGS INDICATE 0-1 HELICITY GREATER THAN 200 M2/S2 AND 0-1KFT 
 SHEAR OF 40 KNOTS THIS AFTERNOON...ESPECIALLY ACROSS CENTRAL 
 VIRGINIA AND LOWER SOUTHERN MARYLAND.
 
 GIVEN ABOVE...THINKING THERE IS A POSSIBILITY FOR MULTIPLE TORNADOES 
 ACROSS THE REGION THIS AFTERNOON. LOCALLY DAMAGING WINDS WILL OCCUR 
 IN VICINITY OF STRONGEST UPDRAFTS. ANOMALOUSLY HIGH PRECIPITABLE 
 WATER VALUES MAY PRODUCE LOCALIZED FLASH FLOODING.
 
 GFS IS PREFERRED MODEL AT THIS TIME GIVEN RECENT ISSUES WITH THE NAM 
 (OVER-DEEPENING TROUGHS IS SLOWING DOWN TIMING OF COLD FRONT). 
 
 &&

 

[midatlanticweather]

Not much - but something

[high risk]

We're now into the range where we can start to see what this looks like in terms of hi-res simulated reflectivity.  Both the NAM Nest and HiResW FV3 at 60 hours have an intense line to our west.   We'll need a speed-up to boost severe potential locally, but a strongly-forced convective line will likely cross the entire region after dark.    Any severe threat, or even lightning potential, will be low due to a loss of diurnal instability, but the dynamics will ensure that both threats are non-zero.  And again, if this speeds up by 3-6 hours,  the threats for lightning and severe will ramp up accordingly.

[Kmlwx]

I always mention this - but anecdotally these convective lines are well know for coming in a bit earlier than progged at range. 

[yoda]

Like the term squeegee line lol... also since when did NWS utilize Nadocast?   Afternoon disco from LWX 

SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
A potent trough of low pressure will move into the northern/eastern
Great Lakes Sunday morning while it`s associated cold front pushes
east from the Ohio River Valley. Meanwhile, high pressure will
reside off the southeast U.S coast leading to increased southerly
flow across the region. With the tightened pressure gradient between
the departing high and incoming front/trough of low pressure expect
a windy end to the weekend.

Dry and windy conditions are expected for most of the day as
moisture steadily increases across the region. Mid and high level
clouds will spread west to east from the Alleghenies Sunday morning
into Sunday afternoon. Some filter breaks of sun will be observed
early east of the I-81 corridor with any rain activity likely
holding off until after sunset. 06Z/12Z CAMS have slowed a bit from
previous model solutions. As it stands now, shower activity looks to
develop west of the Alleghenies/I-81 corridor late Sunday afternoon
before spreading east toward the metros late Sunday evening into
Sunday night. Most guidance illustrates a frontal passage within the
2z-8z/10pm-4am window for areas east of I-81 and toward the I-95
metros. This is the time of greatest moisture surge and perhaps some
subtle instability as the trough axis takes on a negative tilt. CAPE
values look to remain less than 300 j/kg with bulk effective shear
values running between 40-50 kts+. Forcing will be strong especially
along the front. This will allow for both strong background winds
and a strong wind field aloft to mix down to surface with any
convective elements that form along the front.

06z/12z guidance continues to develop a line of gusty moderate to
heavy showers that push from west to east across the area late
Sunday afternoon into Sunday night. A few thunderstorms cannot be
ruled out as well, especially west of I-95 where slightly better
instability noted. SPC has expanded it`s Day 2 Marginal Risk (Level
1 out of 5) to encompass the entire area Sunday afternoon. The main
threat is damaging wind gusts although an isolated tornado cannot be
ruled out given low level SRH 0-1km values around 100-200 m2/s2 and
potential meso-low overhead. Both CSU, CIPS, and NSSL probabilities
focus 5 to 15 percent probs for damaging winds as a squeegee line of
gusty showers push through late Sunday afternoon into Sunday night.
Nadocast has 2 percent probs over northern and central MD mainly
covering the pre-dawn hours of Monday morning.

Additional showers are possible through Monday morning behind the
cold front as the negatively tilted upper-level trough passes
through. This activity will likely be short-lived with dry air
working back in as high pressure builds from the south Monday
afternoon into Monday evening.

[high risk]

MRGL for most of the area which seems fair.    Guidance is now in very good agreement that a strongly-forced, narrow line of heavy showers will race across the area during the evening:  9pm or so in the western burbs, 10pm in the DC-Baltimore area, and over the Bay by around 11.    Wind fields are intense with some low-level shear, but instability will be negligible.    Lightning therefore seems unlikely, and while winds will be gusty, severe gusts will be difficult to achieve.   That said, I still can't completely rule out lightning or a few higher end gusts, and it's also possible that we end up with a tornado warning for someone for a brief couplet.

[WxUSAF]

1 hour ago, high risk said:

MRGL for most of the area which seems fair.    Guidance is now in very good agreement that a strongly-forced, narrow line of heavy showers will race across the area during the evening:  9pm or so in the western burbs, 10pm in the DC-Baltimore area, and over the Bay by around 11.    Wind fields are intense with some low-level shear, but instability will be negligible.    Lightning therefore seems unlikely, and while winds will be gusty, severe gusts will be difficult to achieve.   That said, I still can't completely rule out lightning or a few higher end gusts, and it's also possible that we end up with a tornado warning for someone for a brief couplet.

Looks like it will be a fun 7-12 minutes lol 

[ravensrule]

3 minutes ago, WxUSAF said:

Looks like it will be a fun 7-12 minutes lol 

Definitely more than you are used to. Enjoy.