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.