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.

The forecast center is closed on Sunday.  Please return to this site however and use the SPC homepage link, and the mesoscale discussions and watches maps for updates.

The Storm Prediction Center (SPC) has issued an ENHANCED risk for severe thunderstorms in the current DAY 3 Outlook: OVER MUCH OF THE CAROLINAS…VIRGINIA…AND EXTENDING NORTHWARD INTO SOUTHERN PENNSYLVANIA…

…SPC SUMMARY…
Widespread damaging winds and several tornadoes are forecast on Monday for parts of the Mid Atlantic and Southeast.

HATCHED AREAS depict the probability of  SIGNIFICANT SEVERE WEATHER
SPC DAY 3 SEVERE THUNDERSTORM OUTLOOK (LINKED FOR OUTLOOK TEXT)


The following is the current CSU – MLP severe weather forecast map and NSSL ML probability forecast:
CSU – MLP DAY 3 FORECAST (CLICK FOR LARGER IMAGE)


DAY 3 SPC DISCUSSION EXCERPT:
A large and deepening upper trough will eject east/northeastward out of the MS/OH/TN Valleys and across the Appalachians and into the Mid Atlantic/Northeast on Monday, with an expansive area of strong wind fields aloft. A surface low move from Lower MI into southern Quebec, with a deep pre-frontal trough extending southward across eastern PA, VA, and NC by around 21Z. Ahead of this trough/front, southerly winds will bring 60s F dewpoints as far north as southeast PA.

There are model differences regarding the speed/position of the cold front, as well as the degree of instability. Regardless, damaging winds over a large area appear likely, along with at least a few tornadoes. Depending on the degree of destabilization, a strong tornado or two may occur especially over parts of the Carolinas and Virginia during the late afternoon. Many models forecast 300-500 m2/s2 SRH, along with pockets of SBCAPE over 1000 J/kg, which is clearly favorable for tornadic supercells.

CURRENT SPC DAY 2 OUTLOOK SYNOPSIS
The Storm Prediction Center (SPC) has issued an ENHANCED risk for severe thunderstorms in the current DAY 2 Outlook: IN THE ARK-LA-TEX/ARK-LA-MISS TO THE WABASH/LOWER OH VALLEYS…

…SPC SUMMARY…
Scattered to widespread damaging winds along with tornadoes should develop on Sunday afternoon, persisting through Sunday night across a large portion of the South-Central/Southeast States into the Midwest/Ohio Valley. The greatest strong tornado and significant severe wind threats appear to be from the Ark-La-Miss to the Lower Ohio Valley on Sunday evening.
SPC DAY 2 SEVERE THUNDERSTORM OUTLOOK (LINKED FOR OUTLOOK TEXT)

TORNADO PROBABILITY

Probability of a tornado within 25 miles of a point.  Hatched Area: 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-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.

The following is the current CSU – MLP severe weather forecast map and NSSL ML probability forecast:
CSU – MLP DAY 2 FORECAST (CLICK FOR LARGER IMAGE)

NSSL ML DAY 2 SEVERE PROBABILITY 

DAY 2 PROBABILITY CONVERSION TABLE

SPC DISCUSSION EXCERPT:
…South-Central/Southeast States to the Midwest…
By late afternoon, an extensively long QLCS should become established from IL south-southwestward. Semi-discrete supercell development appears most favored along the southern portion of the broader convective plume near the front and downstream within a strengthening warm/moist conveyor. This should support potential for large hail and a couple strong tornadoes before supercells become absorbed within the broader QLCS during the evening. This scenario should also yield an increasingly pinched-off warm-moist sector from the Mid-South to TN Valley. Despite this aspect, substantial strengthening of 700-mb winds on either side of the front, initially across the Mid-South vicinity and expanding to the OH to TN Valleys, will yield a setup conductive for scattered to widespread damaging wind swaths through the evening.

On Sunday night, the northern extent of the severe threat should become more sporadic as surface-based instability becomes/remains minimal. But the very fast lower-level wind fields may yield persistence of some damaging wind/brief tornado potential eastward in the OH Valley/southern Great Lakes. Farther south, there are increasing signals for renewed low-level warm conveyor convective development across the central to northeast Gulf Coast vicinity early Monday morning. Deep-layer shear profiles will be conducive to semi-discrete supercells just ahead of/merging into the progressive QLCS. This should foster a period of increased large hail/sustained tornado potential. Otherwise, damaging winds will remain favored from at least the FL Panhandle to the southern Appalachians.

NADOCAST maps will not be available until the SPC DAY 1 outlook.  You may access the maps using the following link: http://data.nadocast.com/

Based on my analysis of the preliminary severe weather indices, the forecast calls for high end moderately unstable atmosphere to borderline very unstable.  Indices and current outlook maps indicate ALL severe weather threats are possible, with possible severe hail, severe wind gusts, and strong tornadoes.  The bulk of any tornado activity appears it should be in the (EF2 -EF3) range within the 5% HATCHED TORNADO outline, with the probability of an isolated (EF4 – EF5) within the 10% HATCHED TORNADO outline.  Currently, strongest severe weather indices should be within these outlines. Some indices will most likely change between issuance of this synopsis, and by the onset of the DAY1 outlook, so this forecast should not be taken as absolute.  
CAPE VALUES FORECAST

DEW POINT FORECAST

Based on analysis of model animations, the current outlook, and analysis of indices, the strongest convection and indices should occur by late afternoon through late evening on Sunday, with model animations suggesting the strongest storms to occur between 4:00 p.m. – 11:00 p.m. CDT.  

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

The following were the forecast parameters and indices analyzed this afternoon from the 12Z run of the NAM 3km and current runs of the other listed models.  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: 500 – 2000 j/kg-1                  
MLCAPE: 250 – 1500 j/kg-1                   
MUCAPE: 500 – 2000 j/kg-1                
SRH 0 -1 km: 150 – 300 m2/s2               
SRH 0 -3 km: 200 – 500 m2/s2        
SRH EFFECTIVE: 200 – 400 m2/s2          
L. I.: -1 to -6                                                      
SCP: 2 – 12                                             
STP: 0.1 – 1.4  
0 -6 km SHEAR: 40 kts – 50 kts                  
EFF. SHEAR: 30 kts – 40 kts                        
MID LEVEL LAPSE RATE: 7.5C – 8.5C   
DEWPOINT: 55F – 68F                                    
EHI: 0.3 – 4.7                                         
TOTAL TOTALS INDEX: 52C                      
K INDEX: 28C – 36C                                          
SWEAT INDEX: 475 – 560                             
THOMPSON INDEX: 29 – 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
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 MAR. 15 – 3:00 A.M. CDT MAR. 16

NAM 3KM STP FORECAST 1:00 P.M. CDT MAR. 15 – 3:00 A.M. CDT MAR. 16

NAM 3KM RADAR ANIMATION 1:00 P.M. CDT MAR. 15 – 3:00 A.M. CDT MAR. 16

I have provided the SPC homepage link below, so you may get the updated information regarding any changes to the outlook:
SPC HOMEPAGE
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…SEEK STURDY AND SAFE SHELTER IMMEDIATELY!
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 forecasts, 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)
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