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 evening everyone!

The Storm Prediction Center (SPC) has issued a SLIGHT risk for severe thunderstorms in the current DAY 3 Outlook: FROM THE ARKLATEX ACROSS THE OZARKS AND INTO PARTS OF THE MIDDLE TO LOWER MISSISSIPPI AND OHIO VALLEYS…

…SPC SUMMARY…
Scattered severe thunderstorms are possible Saturday across parts of the Ark-La-Tex, Ozarks, mid Mississippi and lower Ohio Valleys. A few tornadoes, damaging winds and hail will be possible
SPC DAY 3 SEVERE THUNDERSTORM OUTLOOK (LINKED)

The following is the current CSU – MLP severe weather forecast map:
CSU – MLP DAY 1 FORECAST (CLICK FOR LARGER IMAGE)

DAY 3 PROBABILITY CONVERSION TABLE

SPC DISCUSSION EXCERPT
Considerable uncertainty exists regarding the degree of severe storm potential on Saturday, with a range of model solutions regarding trough speed, early day precipitation and air mass quality. At the very least, a broad Slight Risk remains reasonable given these uncertainties.

While low-level moistening combined with cooling aloft will generally lead to increasing instability, several models indicate early/ongoing thunderstorm potential roughly from OK into MO and IL. At the very least, this activity should generally become more organized as the cold front strengthens with increasing large scale ascent, leading to wind damage potential. If the less-amplified solution verifies, potentially strong instability could build during the day, with more of a supercell risk along with tornado/hail potential.

The following maps will not be available until Saturday.
00Z NADOCAST TORNADO PROBABILITY (CLICK FOR LARGER IMAGE)

NADOCAST SIGTOR PROBABILITY (CLICK FOR LARGER IMAGE)
Based on my analysis of the severe weather indices, the forecast calls for a moderately unstable atmosphere at the moment  Indices indicate all severe threats are probable.  Currently, tornadoes are possible, however I am not expecting any strong tornadoes at the moment.  Any tornadoes that occur should be EF0 – EF1.  I do not expect large hail at the moment, unless there are some changes in the indices by Sat.  Damaging thunderstorm gusts are probable as well.

Based on analysis of model animations and the current outlook, strong storm initiation should occur approximately around 3:00 p.m. to 4:00 p.m. CDT.

Regarding the severe indices and EHI values for this synopsis minimum values currently represent the area east and NE of central Arkansas, and higher values from near central Arkansas, westward to the Oklahoma border and extreme eastern Oklahoma.

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

The following were the forecast parameters and indices analyzed this evening.  Bear in mind, 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: 1000 – 2500 j/kg-1                  
MLCAPE: 1000 – 2000 j/kg-1                   
MUCAPE: 1000 – 2500 j/kg-1                
SRH 0 -1 km: 50 – 100 m2/s2               
SRH 0 -3 km: 100 – 200 m2/s2        
SRH EFFECTIVE: 100 – 200 m2/s2          
L. I.: -3 to -6                                                       
SCP: 2 – 6                                                
STP: 1.0 – 2.0     
0 -6 km SHEAR: 50 kts – 60 kts                  
EFF. SHEAR: 40 kts – 50 kts                        
MID LEVEL LAPSE RATE: 7.0C – 7.5C   
DEWPOINT: 60F – 67F                                    
EHI: 0.94 – 1.9                                               
TOTAL TOTALS INDEX: 46C – 47C                        
K INDEX: 32C – 36C                                          
SWEAT INDEX: 250 – 300                             
THOMPSON INDEX: 35 – 42                      
CRAVEN – BROOKS INDEX: 10,000 – 30,000      

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

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 OCT 18 – 10:00 P.M. CDT OCT 18

NAM 3KM STP FORECAST 1:00 P.M. CDT OCT 18 – 10:00 P.M. CDT OCT 18

If possible, I will try to have another update on Saturday.

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)

IF A TORNADO WARNING IS ISSUED FOR YOUR AREA, IMMEDIATELY TAKE STURDY AND SAFE SHELTER
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 any special weather statements, hazards or advisories for your area.
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)
CARIBBEAN RADAR (CLICK IMAGE TO ACCESS ANIMATION)

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

Have a blessed evening!

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