SLIGHT RISK OF SEVERE THUNDERSTORMS SYNOPSIS…ISSUED APR. 30, 2022…10:10 EDT

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(T. F. “Storm” Walsh)

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Please be aware, even though I do not post every night, rest assured I am continuously monitoring various areas for any significant weather.  I will be taking Sundays off (family time), unless we have active systems that may be posing a threat (i.e. Tropical, Winter Weather, Coastal Storms, etc.).

I will reiterate, my forecasts are based on the available information at the time of analysis, and are only as accurate as the information analyzed and the solutions provided.

I will try to update this evening on tomorrows DAY 2 outlook of an ENHANCED risk for severe thunderstorms.

The Storm Prediction Center (SPC), has issued a SLIGHT RISK OF SEVERE THUNDERSTORMS in the current DAY 1 outlook: From the MID-MS VALLEY/MIDWEST TO THE ARK-LA-TEX…

…SPC SUMMARY…
Scattered severe thunderstorms are anticipated this afternoon and evening across portions of the Mid-Mississippi Valley/Midwest towards the Ark-La-Tex. Several tornadoes, damaging winds, and large hail will be possible.

…SPC Synopsis…
Closed mid/upper low over the Mid-MO Valley will drift into the Upper MS Valley through early Sunday, with an attendant occluded surface cyclone taking a similar track. The T-intersection of the surface occlusion is expected to move across the IA/IL/WI border vicinity this afternoon and across far southern WI this evening. The surface cold front will arc to the south-southwest from roughly the Saint Louis area to the Ark-La-Tex in the late afternoon. Trailing portion will then arc west-southwest, bisecting central TX, and become quasi-stationary by evening.

SPC DAY 2 CONVECTIVE OUTLOOK LINK:
https://www.spc.noaa.gov/products/outlook/day1otlk.html

SPC DAY 1 CONVECTIVE OUTLOOK

TORNADO PROBABILITY

HAIL PROBABILITY
DAMAGING THUNDERSTORM WIND PROBABILITY

Based on my analysis of the SPC DAY 1 Outlook, the thermodynamic setup will allow for all hazards.  Analysis of the forecast setup tends to indicate the higher tornado threat may lie within the northern portion of the slight risk area, over portions of the upper Midwest from early afternoon to early evening.  Further south over the ARK-LA-TEX area, the main threat is forecast to be large hail, however analysis of tornado indices indicate a probability for an isolated tornado or two.

Based on my analysis of both the NAM-WRF model from F5 DATA, and the NAM 3 km model, the following forecast severe and tornado indices were analyzed and values represent a blend of both models:
SBCAPE: 1500 – 3000 j/kg
MLCAPE: 1000 – 1500 j/kg
SRH: 200 – 250 m2/s2
L. I.: -2 to -4
SWEAT: 325 – 375
EHI: 1 – 2
VGP: 0.2 – 0.6
STP: 1 – 4

STP EXPLAINED:
A majority of significant tornadoes (F2 or greater damage) have been associated with STP values greater than 1, while most non-tornadic supercells have been associated with values less than 1 in a large sample of RAP analysis proximity soundings.

SCP EXPLAINED
A multiple ingredient, composite index that includes effective storm-relative helicity (ESRH, based on Bunkers right supercell motion), most unstable parcel CAPE (muCAPE) and convective inhibition (muCIN), and effective bulk wind difference (EBWD). Each ingredient is normalized to supercell “threshold” values, and larger values of SCP denote greater “overlap” in the three supercell ingredients. Only positive values of SCP are displayed, which correspond to environments favoring right-moving (cyclonic) supercells.

VGP: The VGP (Vorticity Generation Parameter) is meant to estimate the rate of tilting and stretching of horizontal vorticity by a thunderstorm updraft. Values greater than 0.2 m s^-2 suggest an increasing possibility of tornadic storms.

The following sites will explain most of these values, and will give you an idea of what to expect:
ENVIRONMENTAL INDICES AND PARAMETERS NWS
https://www.weather.gov/lmk/indices

THE WEATHER PREDICTION
http://www.theweatherprediction.com/severe/indices/

The following outlined areas indicate where the modeling suggests the best / highest probabilities for the strongest severe weather and tornadoes could occur.  The strongest of the indices will be located where the SPC has the 5% area probability for tornadoes, with analyzed indices indicating the more stronger values being over the upper Midwest.  Based on analysis of the indices, the values begin to increase at around 1:00 p. m. CDT, and reaching their peak around 4:00 p. m. CDT.  Based on the NAM 3km STP and SCP animations, activity decreases after 4:00 p. m. CDT near 7:00 p. m.  The animations will also show you where the strongest index values lie, within the outlined maps.
F5 DATA NAM – WRF 1:00 P. M. CDT

4:00 P. M. CDT

7:00 P. M. CDT

The following NAM 3km animations indicate the locations and strength of the forecast STP (Significant Tornado Parameter) index, and SCP (Supercell Composite Parameter) index.
NAM 3km STP ANIMATION (1:00 P. M. CDT APR 30 – 7:00 P. M. CDT APR 30)

NAM 3km SCP ANIMATION

Please use the following maps for all days, which should update automatically, for Mesoscale Discussions and Convective Watches.  You may have to refresh your browser, or click on the graphics.  I am also providing the SPC homepage link, so you may get the updated information regarding any changes to the outlook:
SPC MESOSCALE DISCUSSIONS (CLICK IMAGE FOR UPDATES)

SPC CONVECTIVE WATCHES (CLICK IMAGE FOR UPDATES)

SPC HOMEPAGE LINK
https://www.spc.noaa.gov/classic.html
IF A TORNADO WARNING IS ISSUED FOR YOUR AREA, IMMEDIATELY TAKE STURDY AND SAFE SHELTER

The following NWS Watch / Warning map will provide local NWS information for your area.  Click the image, then once it refreshes, click on your area of interest to view any special weather statements, hazards or advisories for your area.
NWS WATCH / WARNING DISPLAY (LINKED…CLICK MAP, THEN YOUR AREA)

WSI DOPPLER RADAR LOOP (LINKED)

RAP RADAR (CLICK IMAGE THEN RADAR SITE)
You may direct any questions by contacting me personally, ANYTIME, at: twalsh22000@yahoo.com

Have a blessed weekend!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST