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!

As we enter into the Atlantic Hurricane Season (June 01), forecasts will transition over to Tropical Weather.  Severe weather updates will still be issued for SLIGHT risks and above, only until the Hurricane Season begins to pick up.  IF severe weather is not pressing, then I will be tracking Tropical Waves. 

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 ENHANCED risk for severe thunderstorms for Sun. and Mon.  There is a SLIGHT risk forecast for Tue. 

Based on the current CSU-MLP probabilities forecast, and text of the current DAY 2 outlook, a possible upgrade to a MODERATE risk for Mon. cannot be ruled out at this time. 

ALL graphics are linked to their outlooks:
DAY 2 OUTLOOK:

DAY 3 OUTLOOK:

SPC DAY 4 – 8 OUTLOOK: 

CURRENT DAY1 SEVERE WEATHER OUTLOOK
The Storm Prediction Center (SPC) has issued an ENHANCED risk for severe thunderstorms in the current DAY1 Outlook: ACROSS PARTS OF THE CENTRAL HIGH PLAINS…

There is a SLIGHT risk for severe thunderstorms in the current DAY1 Outlook: ACROSS PARTS OF THE OHIO VALLEY……SPC SUMMARY…
Severe thunderstorms capable of producing large to very large hail, severe/damaging winds (some 75+ mph), and a few tornadoes should occur this afternoon and evening across parts of the central Plains into Iowa.

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:
…Central High Plains to Iowa..
An increase in convective coverage and intensity is anticipated as this activity spreads eastward across the central High Plains late this afternoon and evening, aided by at least moderate instability and deep-layer shear. While some supercell potential will exist, along with a threat for large to isolated very large hail, most guidance continues to suggest that an intense bowing cluster will develop and spread eastward along/near the surface boundary across southern NE/northern KS through the evening. A greater threat for severe winds, some of which could be significant (75+ mph), remains apparent, as steep low/mid-level lapse rates aid in efficient downward momentum transfer within the convective cluster. A modest expansion has been made to the Enhanced Risk to account for the potential of a slightly larger cluster.

A separate area of robust convective development should also occur farther east this afternoon/evening across parts of IA and vicinity along/near the surface front. This activity will likely be aided by strengthening low-level warm advection this evening, and it may persist through much of the night. The presence of steep mid-level lapse rates, increasing low-level moisture, and daytime heating all suggest that moderate to locally strong instability will likely be in place by late afternoon along/south of the front. While westerly mid-level flow should only be modestly enhanced, sufficient deep-layer shear is forecast to support supercells initially. Large to very large hail (isolated 2+ inches) appears possible within the first couple hours of initiation, before thunderstorm mergers/interactions occur and the overall mode becomes messy. Some increase in the severe/damaging wind threat may develop if a more organized cluster can emerge and spread east-southeastward through the evening and early overnight hours.  A few tornadoes also appear possible through the evening with any sustained supercells. This potential should remain focused along/near the front where backed low-level easterly winds may locally enhance 0-1 km SRH.

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 extremely unstable atmosphere within the ENHANCED and SLIGHT risk outline over Kansas, Nebraska, and Iowa, and the 15% – 30% HATCHED HAIL OUTLINE.  The main severe risk as of analysis this morning is the possibility of damaging thunderstorm winds / gusts in excess of 65 kts, LARGE to SIGNIFICANT hail, and the possibility of  TORNADOES.  The tornado risk is at 5% over the ENHANCED risk area, and a portion of the SLIGHT risk area according to the SPC forecast.  Any tornadoes that occur may range from ( EF1), to an isolated (EF2) (based on the current CIG)

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 animations, current radar, the current outlook, and analysis of indices, the strongest storms 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, 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 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 following were the forecast parameters and indices analyzed this morning within the ENHANCED and SLIGHT risk outline and the 15% – 30% HATCHED HAIL OUTLINE:  
SBCAPE: 1500 – 4000 j/kg-1                  
MLCAPE: 1500 – 3000 j/kg-1                   
MUCAPE: 1500 – 4000 j/kg-1                
SRH 0 -1 km: <100 m2/s2               
SRH 0 -3 km: 100 – 250 m2/s2        
SRH EFFECTIVE: 100 – 200 m2/s2          
L. I.: -4 to -10                                              
SCP: 2 – 15                                   
STP: 0.2 – 2.5
0 -6 km SHEAR: 40 kts – 50 kts                  
EFF. SHEAR: 30 kts – 40 kts                        
MID LEVEL LAPSE RATE: 8.0C – 8.5C 
DEWPOINT: 52F – 72F                                   
SUPERCELL EHI : 0.9 – 4.7
TORNADIC EHI : 0.9 – 3.3                          
TOTAL TOTALS INDEX: 60C                
K INDEX: 22C to 42C                                          
SWEAT INDEX: 615 – 670                   
THOMPSON INDEX: 26 to 52  
CRAVEN – BROOKS INDEX: 10,000 – 50,000     

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 16 – 11:00 P.M. CDT MAY 16

NAM 3KM STP FORECAST 1:00 P.M. CDT MAY 16 – 11:00 P.M. CDT MAY 16

NAM 3KM RADAR SIMULATION 1:00 P.M. CDT MAY 16 – 11:00 P.M. CDT MAY 16

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