2025 Severe Weather General Discussion

[Kmlwx]

Still out in the long range...but the GFS would seem to suggest the doldrums may be coming to an end. CIPS is also starting to latch onto increased severe potential out beyond 200 hours. The 06z GFS run had decent parameters on SEVERAL days out in the long range.

[yoda]

On 5/8/2025 at 8:24 AM, Kmlwx said:

Still out in the long range...but the GFS would seem to suggest the doldrums may be coming to an end. CIPS is also starting to latch onto increased severe potential out beyond 200 hours. The 06z GFS run had decent parameters on SEVERAL days out in the long range.

Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0400 AM CDT Sat May 10 2025

   Valid 131200Z - 181200Z

   ...DISCUSSION...
   Medium-range guidance indicates that a generally amplified, split
   mid/upper flow will persist across the mid-latitude Pacific through
   North America next week.  It appears that this will include at least
   a couple of significant troughs digging inland of the U.S. Pacific
   Coast.  The first may already be in the process of developing
   eastward across the Intermountain West early in this period
   (Tuesday), before progressing across the Rockies, Great Plains and
   Mississippi Valley during the middle through latter portion of next
   week.  This may be followed by another significant trough digging
   inland of the Pacific coast by early next weekend.

   The lead trough will be relatively close on the heels of the
   remnants of an initially broad quasi-stationary/cut-off low, which
   may only slowly progress east of the Mississippi Valley through
   Atlantic Seaboard during the early to middle portion of next week. 
   Low-level moisture return, in the wake of this perturbation and
   ahead of the mid-level trough emerging from the West, may continue
   to be impacted across at least parts of the Great Plains into mid
   week.  Thereafter, there appears a general consensus that there will
   be a better coupling of large-scale forcing for ascent, aided by
   surface cyclogenesis, with a notable increase in low-level moisture
   and destabilization across the lower Missouri Valley into the Upper
   Midwest and lower Ohio Valley by late next Thursday into Thursday
   night.  In the presence of strong shear, it appears that this
   environment could become supportive of supercells and/or one or two
   organizing severe storm clusters.

   Machine learning output and other guidance suggests that potential
   for strong to severe thunderstorms could persist and potentially
   become more widespread across the Ohio Valley into Mid Atlantic, and
   southern Great Plains, next Friday and Saturday.  However,
   uncertainties remain too large at this time to introduce greater
   than 15 percent severe probabilities.

   ..Kerr.. 05/10/2025

[yoda]

Next Friday into the weekend looks intriguing per afternoon AFD from LWX 

After a short reprieve, the system later in the week will have a lot
more fuel to work with. As high temperatures on Friday are expected
to rise into the mid/upper 80s (coupled with dew points approaching
70 degrees), instability should be plentiful. Some strong to severe
thunderstorms are possible as this system tracks through on Friday
into early next weekend. Details hopefully become more apparent in
the next few days.

 

[yoda]

@Kmlwx @Eskimo Joe  @high risk

this sounds great for now lol (from the afternoon AFD from LWX)

As we move toward the end of the week, a deep upper low and
attendant strong surface low will slowly track eastward into the
Upper Great Lakes. As this occurs, rich low-level moisture will be
drawn north and east from the Gulf into the Ohio Valley and Mid-
Atlantic. Simultaneously, a strong belt of mid-level flow (35-50
knots in the 700-500 hPa layer) will spread overtop that rich low-
level moisture, advecting a remnant elevated mixed layer plume
eastward as it does so. Rich low-level moisture, steeper than
climatology mid-level lapse rates, and strong mid-level flow will
result in an environment on Friday, and potentially even Saturday as
well, characterized by both strong instability and strong deep layer
shear. The EPS and GEPS ensemble means have 2000-3000 J/kg CAPE
along with 35-50 knots of 0-6 km bulk shear. The GEFS show lesser
instability and similar shear values, but have a well-know low bias
when it comes to instability. This type of parameter space raises
concerns for severe thunderstorms. While the parameter space being
advertised at the moment by models is toward the higher end of what
we typically see in this part of the country, we`re still at day 6
and 7, and there is plenty of time for things to change, especially
when an upper level low is involved (which models notoriously
struggle with in the long range). With an elevated mixed layer
involved, there are also signs of stronger capping than we typically
see, so that could complicate things as well. For now, the end of
the week is a period to monitor for potential severe thunderstorms,
with the expectation that the forecast can and will change this far out.

[Kmlwx]

If nothing else - instability looks better than prior events so far this year. Still so far out - we'll see. (my famous two words)

[andyhb]

The 12z UK is a must check for shits and giggles for this region.

[Kmlwx]

Would fit well with our little local "tornado alley" down near EZF and across the bay into the La Plata/Southern Maryland area. Seems some of the guidance (not that it matters much at this range) wants to push the main threat to our south. That AI convective NCAR page is honking a bit for the Fri-->Sat timeframe though. 

[high risk]

6 hours ago, Kmlwx said:

Would fit well with our little local "tornado alley" down near EZF and across the bay into the La Plata/Southern Maryland area. Seems some of the guidance (not that it matters much at this range) wants to push the main threat to our south. That AI convective NCAR page is honking a bit for the Fri-->Sat timeframe though. 

 Fri/Sat is definitely worth watching, but there is a lot of disagreement on whether we get decent height falls or if they're focused more north of here.    Any modest height falls would probably bring a severe threat, given the good moisture in place and good wind fields.

[yoda]

Morning AFD from LWX on the threat 

By Fri, another ULL will track eastward toward the Great Lakes. At
the surface, a notable moisture return will occur from the Gulf of
America into the Ohio Valley and Mid-Atlantic Fri into Sat. This
will be coupled with some of the warmest temperatures of the spring
thus far (mid to upper 80s both days), resulting in modest
instability. The combination of low-level moisture, steep low-level
lapse rates, steep for the Mid-Atlantic mid-level lapse rates, and
strong flow will yield the potential for strong to severe
thunderstorms. Depending on timing of cold front, Saturday may be
the more active day, or it may be to the south of the area. Will
continue to monitor. Regardless, the end of the week could yield a
couple days of severe weather. High pressure may briefly move in
Sun, but uncertainties with frontal positioning and the next
shortwave over the Ohio Valley exist.

[Kmlwx]

Cherry picked but just for lulz - it's one of those panels from the NCAR AI convective site. That site seemingly tends to run overly robust to say the least. 

https://www2.mmm.ucar.edu/projects/ncar_ensemble/ainwp/?fbclid=IwZXh0bgNhZW0CMTAAAR3_KcoSRHWhY1lxCTCfOqSNC0AD8SUSmL_c7R_N8rtpvo-PsNNvuY3vuI4_aem_Stpgx3ntIqB8IVErFY76cQ

[frd]

The Northern US cools off over next 5 days as extreme heat in Texas builds and moves North. Interesting boundary may set up for large storms. 

 

 

 

[Kmlwx]

The CFS weeklies with this look could be interesting for us

[yoda]

Some unheard of values for our region showing up on some of the 00z NAM soundings re SHIP... seeing 2.5 to 3.5 values.  Supercell composite lights up quickly Friday afternoon and evening... and lots of significant hail showing up in the SARS, especially some 2" to 4" ones 

June 9 1990 00z IAD 3.50" is one of them

@high risk @Kmlwx @Eskimo Joe

[high risk]

12 minutes ago, yoda said:

Some unheard of values for our region showing up on some of the 00z NAM soundings re SHIP... seeing 2.5 to 3.5 values.  Supercell composite lights up quickly Friday afternoon and evening... and lots of significant hail showing up in the SARS, especially some 2" to 4" ones 

June 9 1990 00z IAD 3.50" is one of them

@high risk @Kmlwx @Eskimo Joe

  Friday is certainly interesting.    To start, several models show some sort of early morning MCS.    The NAM in particular has some steep lapse rates, which likely explains the signals for big hail.    I'm not sure what the trigger would be for afternoon storms to form and take advantage of some positive factors, but it's definitely worth tracking.

 

[Eskimo Joe]

9 hours ago, yoda said:

Some unheard of values for our region showing up on some of the 00z NAM soundings re SHIP... seeing 2.5 to 3.5 values.  Supercell composite lights up quickly Friday afternoon and evening... and lots of significant hail showing up in the SARS, especially some 2" to 4" ones 

June 9 1990 00z IAD 3.50" is one of them

@high risk @Kmlwx @Eskimo Joe

Yea I'm definitely intrigued about Friday's potential. 

[Kmlwx]

If there is in fact morning activity on Friday, it could be one of those days where the morning stuff lays down boundaries to serve as focuses for afternoon storms to trigger. I wonder if Friday is an example of a type of day where coverage may be quite low but the storms that do form will have A LOT of energy all to themselves. Narrow swath of serious hail under a supercell sort of day? 

It's seeming like by Saturday the front might be too far beyond most of us to serve as a 2nd severe day - maybe for eastern areas? 

[frd]

Eastern areas ?

 

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Saturday looks to be the day to monitor for any severe weather.
Forcing strengthens with an incoming potent shortwave digging from
the Great Lakes. At the surface, an area of low pressure slides by
to the north Saturday into Saturday Night, with a cold front
advancing towards and eventually through the region. Temperatures
will climb into the 80s and it will feel quite muggy ahead of the
front. Instability looks to be on the order of around 1000 J/kg with
relatively favorable shear. Thinking any showers and thunderstorms
will come in the afternoon and evening as the front arrives. Main
concern would be damaging wind gusts and heavy downpours, but still
a good amount of uncertainty being a few days out. Coverage in
showers and thunderstorms diminishes into the night with the loss of
daytime heating and passage of the front.

[yoda]

12z NAM continues with the significant hail in the SARS... probably overdone with SBCAPE - suggesting 4000 J/KG... but 21z Friday near DCA is 88/73

Then it really lights up again around 09z SAT... ML Lapse rates are near 8 C/KM and hodos quickly become curved and elongated 

[yoda]

Someone broke the 12z NAM Nest soundings at the end of its run

5000-6000+ SBCAPE because DPs are in the upper 70s

[Kmlwx]

13 minutes ago, yoda said:

Someone broke the 12z NAM Nest soundings at the end of its run

5000-6000+ SBCAPE because DPs are in the upper 70s

I'll go with the under lol...by a lot. 

[Kmlwx]

15 minutes ago, yoda said:

Someone broke the 12z NAM Nest soundings at the end of its run

5000-6000+ SBCAPE because DPs are in the upper 70s

It seems to have that pocket of upper 70s dewpoints to the south of DC in the area surrounding the Tidal Potomac. The dewpoints outside of that little pocket seem more realistic - and subsequently CAPE values seem more realistic as well (and even then may still be on the high side. 

[high risk]

15 minutes ago, Kmlwx said:

It seems to have that pocket of upper 70s dewpoints to the south of DC in the area surrounding the Tidal Potomac. The dewpoints outside of that little pocket seem more realistic - and subsequently CAPE values seem more realistic as well (and even then may still be on the high side. 

        The NAM is doing its usual thing with too high dewpoints, BUT it is forecasting very steep lapse rates for Friday which might be real and would certainly contribute to higher CAPE and a legit large hail threat.    As noted, however, triggers look to be minimal right now, but a high-impact isolated cell or two still seems possible.

[yoda]

10 minutes ago, high risk said:

        The NAM is doing its usual thing with too high dewpoints, BUT it is forecasting very steep lapse rates for Friday which might be real and would certainly contribute to higher CAPE and a legit large hail threat.    As noted, however, triggers look to be minimal right now, but a high-impact isolated cell or two still seems possible.

What do you think of the MCS complex and increasing MLLR/hodographs early Saturday morning the 12z NAM comes up with?