Disclaimer:  This site is not affiliated with the National Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National Weather Service.  ALL forecasts herein are the result of my analysis, (to which you will see me at times, insert excerpts from various agencies due to the nature of the importance of the information) and I am solely responsible for the content.  As ALWAYS, follow the National Hurricane Center, National Weather Service, and your local Emergency Management officials for emergency decisions.  In addition, this is strictly a FORECAST OFFICE.  I CANNOT make decisions regarding travel plans, etc.  My purpose, is to provide you the information, based solely on information I analyze, and the accuracy of the information at hand of the time of analysis, so you may make informed decisions.
(T. F. “Storm” Walsh)

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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.

Good day everyone!

The forecast center is closed on Sunday’s.  Please visit this site on Sunday in order to access SPC products for any severe weather threat.

The Storm Prediction Center indicates a risk for severe weather on Fri. and Sat., with a MARGINAL risk.  ALL graphics are linked to their outlook:
DAY 2 OUTLOOK:

DAY 3 OUTLOOK:

SPC DAY 4 – 8 OUTLOOK: (LINKED TO OUTLOOK)

For a little clarity on the “new” BLACK HATCHED areas, the SPC has added them as CIG or Conditional Intensity Groups.  The higher the category, the stronger that particular weather risk is forecast to be.  The following links explain this new feature, along with a video from the SPC:
NWS 
https://www.weather.gov/news/262402-spc

SPC
https://origin-west-www-spc.woc.noaa.gov/about/outlooks/#:~:text=The%20SPC%20will%20represent%20these%20intensity%20forecasts,product%2C%20replacing%20the%20current%20operational%20’SIGN’%20label.

IF 1300Z SPC DAY 1 outlook graphics are utilized, please check the SPC site for any updates to the outline risks when they are issued.  The next update is issued at 1630Z (12:30 p.m. EDT) 

CURRENT DAY1 SEVERE WEATHER OUTLOOK
The Storm Prediction Center (SPC) has issued a MARGINAL risk for severe thunderstorms in the current DAY1 Outlook: ACROSS PARTS OF TEXAS AND COASTAL/SOUTHERN LOUISIANA…

…SPC SUMMARY…
Thunderstorms with isolated large hail and gusty winds will be possible mainly this evening and tonight across parts of southwest/south-central Texas towards the middle Texas Coast, and this afternoon across coastal/southern Louisiana.

1300Z SPC DAY 1 SEVERE THUNDERSTORM OUTLOOK (LINKED FOR OUTLOOK TEXT)

TORNADO PROBABILITY

Probability of a tornado within 25 miles of a point.  Hatched area: a 10% or greater probability of  EF2 – EF5 tornadoes within 25 miles of a point
HAIL PROBABILITY

Probability of one inch diameter hail or larger within 25 miles of a point. Hatched area: a 10% or greater probability of 2.0 inch diameter or larger hail within 25 miles of a point 
DAMAGING THUNDERSTORM WIND PROBABILITY

Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.  Hatched area: a 10% or greater probability of 65 kt+ winds within 25 miles of a point

CSU – MLP DAY 1 AND 2 FORECAST PROBABILITIES (CLICK FOR LARGER IMAGE)

NSSL ML DAY 1 PROBABILITY

CSU – MLP 6 PANEL PROBABILITIES DAY 3 – DAY 8 FORECAST (CLICK FOR LARGER IMAGE)


DAY 1 PROBABILITY CONVERSION TABLE

SPC DISCUSSION EXCERPT:
…Texas…
Strong westerly mid-flow will be maintained across the southern Plains into the Southeast today, as a mid/upper-level low currently off the coast of Baja California quickly moves eastward through the period. A surface front is currently stalled across parts of south TX, and most of the thunderstorms forecast to develop across TX through tonight are expected to remain elevated. Ascent preceding the shortwave trough should eventually encourage convection to develop near the TX Big Bend late this evening, and spread eastward towards the middle TX Coast through early Friday morning. Sufficient MUCAPE and strong cloud-layer shear will support an isolated threat for severe hail with any elevated supercells that can develop. Strong to locally damaging winds may also occur as supercells encounter greater instability across south-central to coastal TX late tonight, even if they remain slightly elevated. Overall confidence in coverage of severe convection remains too low to include greater severe hail probabilities and a Slight Risk with this update.

…Coastal/Southern Louisiana…
A convectively reinforced surface front is draped across southern/coastal LA this morning, with thunderstorms ongoing to its north. Greater instability will exist to the south of the front across coastal LA this afternoon. Thunderstorms that develop/move across the front later today could pose some risk for locally damaging winds and marginally severe hail given weak to moderate instability and strong deep-layer shear.

The following maps are from NADOCAST for tornado and hail probabilities.  Click each image for a larger view.  
12Z NADOCAST TORNADO PROBABILITY

12Z NADOCAST SIGTOR PROBABILITY 

12Z NADOCAST HAIL PROBABILITY 

12Z NADOCAST SIGHAIL PROBABILITY 

Based on my analysis this morning of the current forecast severe weather indices, the forecast calls for a marginally unstable to moderately unstable atmosphere within the MARGINAL risk outlines and 5% HAIL OUTLINES.  The main severe risk as of analysis this morning appears to be a possibility of HAIL to isolated MARGINALLY SEVERE HAIL, and damaging thunderstorm winds / gusts. The tornado risk is less then 2% over the risk outlines.  Should any isolated tornado activity occur, it should be weak.

Based on analysis of mainly model animations, the current outlook, and analysis of indices, the strongest convection and indices should occur approximately between late afternoon through late evening.  Please visit the SPC homepage via the link provided for any changes to the forecast today.
CAPE VALUES FORECAST

DEW POINT FORECAST

Indices were analyzed from the NAM 3KM, HRRR 3KM, CIPS DETERMINISTIC, and SPC SREF model guidance.

REGARDING EHI VALUES: While EHI values are calculated utilizing MLCAPE and 0 – 3 km SRH values (MLCAPE x 0 – 3 km SRH /160,000) FOR SUPERCELL development, and MLCAPE and 0 -1 km SRH for tornado development.  The highest SRH values do not always fall within ample, highest MLCAPE values for the best probability of tornado activity. I utilize the SRH and MLCAPE values over the area that has the highest tornado risk potential.  Maximum EHI values are calculated within the area(s) that have the greatest probability for tornado activity.  

The following were the forecast parameters and indices analyzed this morning within the MARGINAL risk outlines and the 5% HAIL OUTLINES.  Surprisingly, indices were the same for both outlines, except for mid level lapse rates.  Listed indices will always pertain to the area(s) located within the highest SPC risk outlines, based mainly on indices regarding a higher tornado potential, should multiple severe risk areas appear in the SPC forecast.  Although certain indices may appear stronger on a forecast map, given the lack of other indices does not contribute to the overall severe risk.  Bear in mind, MAXIMUM indices recorded below are for the time of peak intensity.  Some indices meanings are posted below the indices themselves, and the NWS page containing a more extensive explanation can be accessed further on in the synopsis:
SBCAPE: 500 – 2500 j/kg-1                  
MLCAPE: 500 – 2000 j/kg-1                   
MUCAPE: 500 – 2500 j/kg-1                
SRH 0 -1 km: 50 – 150 m2/s2               
SRH 0 -3 km: 150 – 250 m2/s2        
SRH EFFECTIVE: 50 – 100 m2/s2          
L. I.: -3 to -6                                                
SCP: 2 – 6                                     
STP: 0.3 – 0.7
0 -6 km SHEAR: 50 kts – 70 kts                  
EFF. SHEAR: 40 kts – 50 kts                        
MID LEVEL LAPSE RATE: 6.0C – 6.5C (Louisiana)   7.0C – 7.5C (Texas)
DEWPOINT: 58F – 73F                                    
SUPERCELL EHI : 0.5 – 2.8
TORNADIC EHI : 0.2 – 0.8                            
TOTAL TOTALS INDEX: 50C                
K INDEX: 22C to 36C                                          
SWEAT INDEX: 365 – 400                   
THOMPSON INDEX: 25 to 42    
CRAVEN – BROOKS INDEX: 10,000 – 30,000     

The following are some severe weather parameters and indices explanations:
CAPE

ENERGY HELICITY INDEX

K INDEX

TOTAL TOTALS INDEX

STORM RELATIVE HELICITY

LIFTED INDEX

SWEAT VALUES

THOMPSON INDEX

Craven SigSvr Parameter:
The simple product of 100mb MLCAPE and 0-6km magnitude of the vector difference (m/s; often referred to as “deep layer shear”) accounts for the compensation between instability and shear magnitude. Using a database of about 60,000 soundings, the majority of significant severe events (2+ inch hail, 65+ knot winds, F2+ tornadoes) occur when the product exceeds 20,000 m3/s3.

A little fact on SRH values and tornadoes from NOAA / NWS
Storm Relative Helicity (m² s^-2)
SRH (Storm Relative Helicity) is a measure of the potential for cyclonic updraft rotation in right-moving supercells, and is calculated for the lowest 1-km and 3-km layers above ground level. There is no clear threshold value for SRH when forecasting supercells, since the formation of supercells appears to be related more strongly to the deeper layer vertical shear. Larger values of 0-3-km SRH (greater than 250 m² s^-2) and 0-1-km SRH (greater than 100 m² s^-2), however, do suggest an increased threat of tornadoes with supercells. For SRH, larger values are generally better, but there are no clear thresholds between non-tornadic and significant tornadic supercells.

STP ( Significant Tornado Parameter) EXPLAINED:
A majority of significant tornadoes (EF2 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 (Supercell Composite Parameter) 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.

The following are the SCP (Supercell Composite Parameter) and STP (Significant Tornado Parameter) forecast maps from the NAM 3KM model.  Generally, the higher the values and brighter the color, indicates a greater probability of strong thunderstorm and / or tornadic activity over an area:
NAM 3KM SCP FORECAST 1:00 P.M. CDT APR. 30 – 11:00 P.M. CDT APR. 30

NAM 3KM STP FORECAST 1:00 P.M. CDT APR. 30 – 11:00 P.M. CDT APR. 30

NAM 3KM RADAR SIMULATION 1:00 P.M. CDT APR. 30 – 11:00 P.M. CDT APR. 30

Please use the following maps, which should update automatically, for Mesoscale Discussions and Convective Watches.  You may have to refresh your browser, or click on the graphics.  I have provided the SPC homepage link below, so you may get the updated information regarding any changes to the outlook:
https://www.spc.noaa.gov/classic.html
SPC MESOSCALE DISCUSSIONS (CLICK IMAGE FOR UPDATES)

SPC CONVECTIVE WATCHES (CLICK IMAGE FOR UPDATES)

The following sites will explain most of the severe weather and tornado values listed above, 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 links will connect you to the Excessive Rainfall probabilities and River Flood Outlook:
EXCESSIVE RAINFALL
https://www.wpc.ncep.noaa.gov/qpf/excessive_rainfall_outlook_ero.php

SIGNIFICANT RIVER FLOOD OUTLOOK
https://www.wpc.ncep.noaa.gov/nationalfloodoutlook/index.html

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 forecasts, any special weather statements, hazards or advisories for your area.
IF A TORNADO WARNING IS ISSUED FOR YOUR AREA…SEEK STURDY AND SAFE SHELTER IMMEDIATELY!

NWS WATCH / WARNING DISPLAY (LINKED…CLICK MAP, THEN YOUR AREA)

NWS DOPPLER RADAR LOOP (LINKED, CLICK RADAR MAP)

RAP RADAR (CLICK IMAGE THEN GO TO LOOP DURATION AND PICK LENGTH OF LOOP, THEN CLICK RADAR SITE)
WUNDERGROUND RADAR SUMMARY MAP (CLICK FOR UPDATES)

PRECIPITATION TYPE (CLICK TO ACCESS ANIMATION FEATURE)

CARIBBEAN RADAR (CLICK IMAGE TO ACCESS ANIMATION)

You may direct any questions by contacting me personally, ANYTIME, at: [email protected]

Have a blessed day!

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