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Severe Weather Threat April 1-4

CheeselandSkies

CheeselandSkies

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Pretty good signal in the models now for some severe weather each of these three days, although nothing particularly high-ceiling at this time. Today-Tuesday can still be discussed in the general seasonal thread.
 
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Honestly, I'm not getting up in the RRFS hype of Thursday for reasons but condolences to @CheeselandSkies due to the fact this setups in his backyard and he has to fly out to OK for chase tour.

I still think a ceiling for discrete cells capable of a strong tornado or two. Due to the lack of any more robust return on the EURO or NAM, I'm gonna hold my guard and not get caught up just yet. We've seen setups like this before, particularly one in 2020 that most of you may remember.... Not saying that Thursday will be anything like that but just important to note to not get caught up in these model runs regardless of their potent solutions. Right now though, this day has seemingly uptrended out of nowhere.
 
998 mb low centered in Colorado around 03z with partially discrete convection merging into a QLCS later on. Some issues regarding storm mode and what it will be on Wednesday but a better ceiling for strong tornadoes may be realised if more discrete. If mode is linear then it's QLCS spam. 00z NAM is in for Thursday, we will see how it goes
 
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Not much of a volatile run, SW surface winds perhaps affecting the magnitude of low level shear, would need a bit more backing to take place. Run is far more conducive to discrete cells with a tornado threat though, and we'll see how that trends
 
WeathermanLeprechaun said:
Not much of a volatile run, SW surface winds perhaps affecting the magnitude of low level shear, would need a bit more backing to take place. Run is far more conducive to discrete cells with a tornado threat though, and we'll see how that trends
Click to expand...

0Z RRFS-A not so impressive either, with minimal instability (although of course it manages to blow up quite a few simulated storms with UH swaths). Seems both models have shifted towards a more strung-out low on this set of runs.
 


Only been public for about a month but from what I've seen these storm-net medium range probabilities are very skillful. I recommend going through the account and looking through the examples.



Models to seem to be split currently between an ECM/UKMET scenario - which in my opinion would be a tornado outbreak, including intense tornadoes, and scenarios where the shortwave ejects slightly too quickly and the strongest windfields don't align with the instability axis, and the majority of storms occurr further East (NAM, GFS). Will just be a case of watching the trends and seeing what happens.

1774946169969.png1774946252883.png

But that being said, I'm extremely surprised the SPC has only gone for a Marginal Risk at Day 3 (for the current focus area).
 
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day3otlk_0730.png
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE MIDWEST AND GREAT LAKES...

...SUMMARY...
Bands of strong to severe thunderstorms are expected across portions
of the Midwest and Great Lakes regions Thursday afternoon. The
primary hazard will be severe gusts, but a tornado or two will also
be possible.

...Synopsis...
A surface cyclone is forecast to deepen as it accelerates
northeastward towards the upper MS Valley in tandem with an upper
trough through the day Thursday. Residual thunderstorms will likely
be ongoing across the Ozarks and will track northeast within a
strengthening wind field. Re-intensification appears likely by
mid-afternoon from lower MI southwestward into IL and IN. Additional
thunderstorm development is anticipated along a trailing cold front
across the mid-MS Valley through the afternoon. Elsewhere, more
loosely organized convection is expected across the lower MS Valley
and along the Appalachians.

...Midwest/Great Lakes...
A combination of northward moisture advection and diurnal heating
will likely support a re-intensification of residual convection
emanating out of MO by mid-afternoon. Winds through the 925-850 mb
layer are forecast to increase to 45-55 knots through the day, which
will support organized convective lines with an attendant threat for
damaging/severe gusts. Additionally, forecast soundings generally
depict strong veering above 1 km AGL, which coupled with hodograph
elongation through the lowest 1-3 km, will support effective SRH
values on the order of 250-350 m2/s2 and a tornado threat with the
more intense/robust lines. That said, the degree of destabilization
ahead of this activity remains uncertain with guidance generally
depicting MLCAPE values on the order of 500 J/kg. While somewhat
meager, the strong flow fields will likely compensate and support a
severe wind threat. 15% probabilities were introduced from eastern
IL northeastward into MI where confidence in the overlap of strong
low-level flow and MLCAPE near 500 J/kg is highest.

Further to the west, additional thunderstorm development is
anticipated along the primary synoptic cold front across the
mid/upper MS Valley. As with the activity further east, this
convection will develop within a modestly buoyant, but strongly
sheared environment that should favor a damaging wind threat.
Confidence in destabilization is somewhat more limited owing to
uncertainty on how quickly early-morning showers/thunderstorms will
exit the region and allow for adequate diurnal destabilization.
 
day4prob.gif

...DISCUSSION...
Severe weather potential will persist through the remainder of the
work week and into parts of the weekend as an amplified upper wave
and attendant surface low traverse the country. The cold front
associated with the late-week storm system will most likely push
south into the Gulf by Sunday as high pressure builds across the
eastern two-thirds of the country and short-wave ridging builds
aloft. This will likely limit the potential for widespread severe
thunderstorms for the early portion of next week.

...D4/Friday - Lower Missouri Valley into the southern Plains...
The approach of an upper wave into the central U.S. will support
steady intensification of a surface low across eastern KS and into
the lower MO River Valley through the day Friday. This will support
a northward flux of low to mid 60s dewpoints through the day, which
should yield SBCAPE values on the order of 2000 to perhaps 3000 J/kg
across northern OK into eastern KS and far western MO by late
afternoon based on a consensus of model solutions. Thunderstorm
development is expected as a cold front slowly begins to push
southeast and overtakes a surface trough/dryline. Deep-layer shear
vectors and storm motions off the boundary should promote initially
discrete cells, though upscale growth is anticipated by the evening
hours amid persistent ascent along the front. Regardless, long-range
guidance has shown a consistent signal for a robust convective
environment over the past 48 hours, and the favorable alignment of
both deterministic and ensemble guidance lends high confidence in a
severe threat emerging across this region Friday afternoon and
evening.
 
Tomorrow. @CheeselandSkies may want to add April 1.


..SOUTHERN KANSAS INTO OKLAHOMA AND NORTHWEST TEXAS

INITIATION ALONG THE DRYLINE APPEARS LIKELY DURING THE 21-00 UTC
PERIOD ACROSS WESTERN OK INTO NORTHWEST TX AS A COMBINATION OF
DIURNAL HEATING AND INCREASING SYNOPTIC ASCENT ACT TO ERODE
INHIBITION. ELONGATED HODOGRAPHS FEATURING EFFECTIVE BULK SHEAR
VALUES BETWEEN 35-45 KNOTS WILL SUPPORT INITIALLY DISCRETE
SUPERCELLS CAPABLE OF LARGE/VERY LARGE HAIL AND TORNADOES (THOUGH
UNCERTAINTY PERSISTS REGARDING LOW-LEVEL SRH THROUGH EARLY EVENING).
UPSCALE GROWTH IS ANTICIPATED AT SOME POINT DURING THE EVENING
HOURS, THOUGH THERE IS SOME UNCERTAINTY ON WHEN THIS TRANSITION WILL
OCCUR AND THE PRIMARY THREAT BECOMES SEVERE WIND. REGARDLESS, AN
INCREASE IN THE NOCTURNAL JET WILL ENLARGE LOW-LEVEL HODOGRAPHS AND
MAINTAIN THE TORNADO POTENTIAL INTO THE LATE EVENING HOURS.

..EASTERN KANSAS AND WESTERN MISSOURI

LATEST GUIDANCE SHOWS FAIRLY STRONG CONSISTENCY IN THE DEVELOPMENT
OF SEMI-DISCRETE CONVECTION ALONG THE LIFTING WARM FRONT ACROSS
EASTERN KS INTO WESTERN MO DURING THE LATE AFTERNOON/EVENING HOURS -
LIKELY OWING TO WEAKER CAPPING AND FOCUSED LOW/MID-LEVEL WARM
ADVECTION THAT IS NOTED IN MOST FORECAST SOUNDINGS. VEERING WINDS
WITHIN THE WARM FRONTAL ZONE WILL SUPPORT EFFECTIVE SRH VALUES ON
THE ORDER OF 200-300 M2/S2, AND SURFACE-BASED LCLS NEAR OR BELOW 1
KM WILL LIKELY SUPPORT A TORNADO THREAT IN ADDITION TO LARGE/VERY
LARGE HAIL. WHILE THE POTENTIAL FOR ROBUST SUPERCELLS IS NOTED, THE
WEAK CAPPING AND FOCUSED ASCENT MAY PROMOTE THUNDERSTORM CLUSTERING
AND UPSCALE GROWTH (AS HINTED BY 00Z HRRR/RRFS SOLUTIONS) THAT COULD
LIMIT THE LONGEVITY OF THESE THREATS; HOWEVER, THE STRONG SIGNAL IN
GUIDANCE FOR DEEP CONVECTION WITHIN A FAVORABLE ENVIRONMENT WARRANTS
AN EXPANSION OF PROBABILITIES.
 
Normally I'd throw out the RRFS but it hasn't been entirely atrocious this year, I suppose. I still am not going to hold it to a higher regard like I do the HRRR. An uptrend on the RRFS to me is simply just an increase in the possible ceiling of the event - but I will say Thursday definitely has a shot at being a solid severe weather outbreak with tornadoes.
 
I agree with the D3 by the SPC. All of these RRFS spam posters I've seen on X is wild. Unless I see a adequate trend to support it elsewhere, Thursday is currently a low confidence day. As for tmrw, E KS and SW OK are of interest. Mode may be more discrete then expected by 03z or it may be clusters. Should a more spaced out mode take place, strong tor threat would be higher. If it clusters, several embedded tornadoes likely. Strong tornadoes maybe becoming more probable on the front in E KS.

I might receive backlash on this one, but so far, Thursday is a split scenario and there's no really way to certify how it will go. I will edge on the side of caution here.

Maybe a tad bit surprised since the NAM does suggest some window after dark for a discrete cell or two in IL with tor threat (possibly strong) but not anything widespread. I probably would've extended the Slight since the NAM solution and Euro solution isn't entirely a all nothing for Central IL.
 
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slenker said:
Normally I'd throw out the RRFS but it hasn't been entirely atrocious this year, I suppose. I still am not going to hold it to a higher regard like I do the HRRR. An uptrend on the RRFS to me is simply just an increase in the possible ceiling of the event - but I will say Thursday definitely has a shot at being a solid severe weather outbreak with tornadoes.
Click to expand...
Agree on all counts. Though I'll just say that the RRFS did pretty well with 3/10. Outside of that though I wouldn't trust it nearly as much as other CAMs. Especially this far out.
 
WeathermanLeprechaun said:
As for tmrw, E KS and SW OK are of interest. Mode may be more discrete then expected by 03z or it may be clusters. Should a more spaced out mode take place, strong tor threat would be higher. If it clusters, several embedded tornadoes likely. Strong tornadoes maybe becoming more probable on the front in E KS.
Click to expand...

In my honest opinion, as of right now, tomorrow looks to have a better shot for tornadoes as a whole. The environment at play is supportive of strong tornadoes and a more discrete mode, or even semi-discrete would have the potential for several strong tornadoes and an intense tornado or two wouldn't be out of the question either.

My eye right now is mainly on SW OK. If cells can stay discrete enough and mature then strong tornadoes are a plausible outcome.
 
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