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.

Tropical Cyclone formation is not expected during the next 5 – 7 days.

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 MARGINAL risk for severe thunderstorms for Sat. and Sun. The following graphics are linked to their outlooks:
DAY 2 OUTLOOK:
DAY 3 OUTLOOK:
SPC DAY 4 – 8 OUTLOOK: 
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 SLIGHT risk for severe thunderstorms in the current DAY1 Outlook: FOR THE TEXAS
PANHANDLE AND NORTHWEST TEXAS INTO SOUTHWEST OKLAHOMA…

…SPC SUMMARY…
Thunderstorms with large to very large hail and severe gusts are
possible late this afternoon into the evening in parts of the
southern High Plains.

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:
…Southern High Plains…
Model forecast soundings show relatively cool 500-mb temperatures
(near -14 deg C) with steep low- to mid-level lapse rates later this
afternoon. Strong heating will locally erode appreciable remaining
convective inhibition and widely scattered thunderstorms will likely
develop by late afternoon. Although westerly flow will likely
remain modest (20 kt from 600 to 200 mb), strongly veering flow will
result in 25-30 kt effective shear, supporting supercells initially.
Large to very large hail will be possible with the more intense
updrafts. Increasing storm coverage during the evening will tend to
promote some upscale growth into a linear cluster with severe gusts
becoming more prevalent. The risk for severe gusts (60-80 mph) may
focus during the 00-03 UTC period before a gradual waning in
coverage/intensity by late evening.

…Central Gulf Coast States/Ohio and Tennessee Valleys...
Models generally show weak
buoyancy (500-1000 J/kg MLCAPE) and skinny CAPE profiles and
tempered lapse rates (reference the Nashville and Birmingham 12 UTC
raobs). However, models show some enhancement/strengthening of
925-500 mb flow moving northeastward across MS/AL into TN through
the mid-late afternoon. As a result, some enlargement of hodographs
will likely occur during the diurnal heating cycle and a few weak
supercell structures will probably develop. Yet, the ongoing
thunderstorm band over eastern MS may be ill timed as it moves
northeastward across western/northern AL through midday.
Nonetheless, an isolated risk for a tornado seems possible over much
of this general region. A risk for isolated damaging gusts may also
accompany some of the stronger thunderstorms before this activity
wanes by the early evening.

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, the current forecast severe weather indices call for a moderately to very unstable atmosphere within the SLIGHT risk outline over Texas, and the 15%  HATCHED HAIL OUTLINE.,  and a mostly moderately unstable atmosphere over the TN Valley region. The main severe risk as of analysis this morning is the possibility of damaging thunderstorm winds / gusts, LARGE to VERY LARGE hail, and the possibility of TORNADOES.  The tornado risk is at 2% over the SLIGHT risk area for Texas and the TN Valley. Any tornadoes that occur should be weak (EF0 – EF1)

The hatched areas you occasionally see in the graphics are referred to as a CIG (Conditional Intensity Grouping), and is explained in the links below:

The following is from the SPC and NWS explaining this feature:
https://www.spc.noaa.gov/exper/conditional-intensity-information/
https://www.weather.gov/news/262402-spc

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

DEW POINT FORECAST

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, MLCAPE and 0 -1 km SRH are used for tornado development.  The highest SRH values do not always fall within ample, highest MLCAPE values for the best probability of tornado activity. Supercell EHI values should be regarded as to how strong supercells may become, and not the reference of tornado intensities listed.  Tornadic EHI should be used to determine the probable strength of any tornadoes.  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.  

If there is a lack of sufficient 0 – 1 km SRH, effective (EFF.) SRH will be used in calculation of tornadic EHI.  From research: (Effective Layer SRH: Recent research suggests using “effective layer” SRH (usually 1250-2250m AGL) as a superior substitute for 0-1 km SRH, as it better represents the inflow layer for supercells).

EHI INDICES are for the guidelines listed above.  Listed indices will always pertain to the area(s) located within the highest SPC risk outlines, based mainly on SBCAPE indices, and / or 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.

The indices listed on the left this morning will pertain mainly to the the area of Texas, where the strongest hail threat is outlined.  Some indices for the TN Valley outline have been added on the right.

The following were the forecast parameters and indices analyzed this morning within the SLIGHT risk outline and the 15% HATCHED HAIL OUTLINE:  
SBCAPE: 1500 – 3500 j/kg-1……….750 – 3000 j/kg-1                    
MLCAPE: 1500 – 2500 j/kg-1…….. 500 – 2000 j/kg-1                   
MUCAPE: 1500 – 3500 j/kg-1………750 – 3000 j/kg-1                
SRH 0 -1 km: <100 m2/s2…………….100 – 225 m2/s2              
SRH 0 -3 km: 100 – 150 m2/s2………100 – 350 m2/s2        
SRH EFFECTIVE: 50 – 100 m2/s2…….100 – 200 m2/s2          
L. I.: -6 to -10                                              
SCP: 2 – 7
STP: 0.1 – 0.7
0 -6 km SHEAR: 30 kts – 35 kts                  
EFF. SHEAR: 25 kts – 30 kts                        
MID LEVEL LAPSE RATE: 8.5C – 9.5C……..5.0C – 6.0C
DEWPOINT: 57F – 64F                                   
SUPERCELL EHI : 0.9 – 2.3……..1.1 – 1.3
TORNADIC EHI : 0.8 – 0.9………..0.7 – 1.3                          
TOTAL TOTALS INDEX: 59C……..51C         
K INDEX: 24C to 36C                                          
SWEAT INDEX: 540 – 570……..430 – 495                  
THOMPSON INDEX: 27 to 45   
CRAVEN – BROOKS INDEX: 10,000 – 30,000……..5,000 – 20,000      

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 MAY 22 – 11:00 P.M. CDT MAY 22

NAM 3KM STP FORECAST 1:00 P.M. CDT MAY 22 – 11:00 P.M. CDT MAY 22

NAM 3KM RADAR SIMULATION 1:00 P.M. CDT MAY 22 – 11:00 P.M. CDT MAY 22

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