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!
I wanted to mention again, for those of you that receive my forecasts, they may not directly apply to you or your area.  However, I have no way of knowing whether or not you have family, or friends that may reside in the affected areas, hence the receipt of the forecasts.

The Storm Prediction Center (SPC) has issued a SLIGHT risk for severe thunderstorms in the current DAY 1 Outlook: ACROSS WESTERN PORTIONS OF WASHINGTON/OREGON… and a MARGINAL risk for the TEXAS LOWER RIO GRANDE RIVER VALLEY.

…SPC SUMMARY…
Severe thunderstorms are expected across parts of the Pacific Northwest this afternoon and evening, with supercells possible west of the Cascades across Oregon into Washington. These storms may produce large hail, perhaps a tornado or two, and strong wind gusts.
SPC DAY 1 SEVERE THUNDERSTORM OUTLOOK (LINKED)

TORNADO PROBABILITY

Probability of a tornado within 25 miles of a point.
HAIL PROBABILITY

Probability of one inch diameter hail or larger 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.
The following is the current CSU – MLP severe weather forecast map:
CSU – MLP DAY 1 FORECAST (CLICK FOR LARGER IMAGE)


DAY 1 PROBABILITY CONVERSION TABLE

SPC DISCUSSION
…Pacific Northwest… Satellite imagery this morning shows an upper low approaching the coast with mostly sunny skies over much of the region. A 100 kt 500-mb speed max will rotate through the base of the trough and overspread coastal OR/WA by mid evening as the upper low shifts east. An associated cold front should arc from off the Washington Coast to southward along the Oregon Coast by evening.

Cold-air advection in the mid levels and diurnal heating will contribute to steepening lapse rates, and the development of weak to locally moderate buoyancy (250-1500 J/kg SBCAPE) by mid-late afternoon. Strengthening large-scale forcing for ascent and negligible CINH will favor isolated thunderstorms developing by mid-late afternoon and increasing in coverage through the early evening. Forecast hodographs indicate supercells are likely with the stronger, more persistent updrafts. Large hail (1-2 inches in diameter) will be possible. The elongated and perhaps locally augmented hodograph in the vicinity of terrain favored areas (i.e., near the Columbia River with a modest easterly component) may enable a short-duration tornado risk. Severe gusts are also possible with the stronger cores and outflow surges as convection matures during the evening and gradually diminishing late.

…Texas Lower Rio Grande River Valley…
A weak disturbance will approach the Rio Grande through mid afternoon with a cirrus shield expected to persist through peak heating. A moist boundary layer sampled by morning area raobs and some filtered heating will promote widely scattered to scattered storms developing this afternoon. Relatively weaker flow in the low to mid levels will limit overall storm organization, but transient supercell/multicells are possible. The stronger storms may be capable of a localized hail/wind threat.

…Southwest IA…
A strengthening warm-air advection regime overnight from KS into MO/IA will likely lead to the development of widely scattered showers/thunderstorms in the vicinity of a warm front. Forecast soundings show elevated instability (1000 J/kg MUCAPE) developing as the profile moistens near 850 mb. A stronger storm capable of small to marginally severe hail cannot be ruled out, but the threat appears too limited to introduce low-severe probabilities.

The following map indicates the probability for tornadoes for today and this evening.
NADOCAST TORNADO PROBABILITY (CLICK FOR LARGER IMAGE)

Based on my analysis of the severe weather indices, the forecast calls for a marginally to weak moderately unstable atmosphere.  Indices indicated the main severe threat for the period should be the potential for hail, some possibly significant over a portion of Oregon and Washington state, with the probability of large hail over the outline in Texas.  Damaging thunderstorms winds and gusts are also probable in both outlined areas. Analysis, SRH and EHI values, along with current forecast CAPE values indicate isolated tornado activity may occur within the strongest cells, however the threat based on the SPC outline and NADOCAST forecast appears low, and if any tornado activity occurs, it should be weak. Based on analysis of model animations and the current outlook, I expect storms to initiate at approximately 1:00 P.M. PDT – 2:00 P.M. PDT over Oregon and Washington state, and between 3:00 P.M. CDT – 4:00 P.M. CDT over Texas, with the strongest period from 7:00 P.M. PDT – 8:00 P.M. PDT over the NW and 7:00 P.M. CDT – 10:00 P.M. CDT, then diminishing thereafter.

Regarding the EHI values for this synopsis, the minimum value will represent indices outside of the MARGINAL risk outlines, and maximum values within the SLIGHT risk and 5% TORNADO outline for the NW, and within the 5% hail outline for Texas.

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

The following were the forecast parameters and indices analyzed this afternoon, with the maximum values pertaining to the SLIGHT risk outline for the NW, and MARGINAL risk outline for Texas.  Bear in mind, indices recorded below are for the time of peak intensity.  Since two areas have been designated for severe weather risks, the indices on the left are for the NW, and the indices on the right are for Texas.  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 – 1750 j/kg-1                   750 – 1250 j/kg-1 
MLCAPE: 250 – 750 j/kg-1                      500 – 1000 j/kg-1 
MUCAPE: 1000 – 1500 j/kg-1                 500 – 1250 j/kg-1 
SRH 0 -1 km: 50 – 150 m2/s2                 100 – 150 m2/s2 
SRH 0 -3 km: 200 – 400 m2/s2             200 – 300 m2/s2 
SRH EFFECTIVE: 0 – 100 m2/s2           100 – 200 m2/s2 
L. I.: -1 to -4                                                       -3 to -5
SCP: 2.0 – 11.0                                                   2.0 – 7.0
STP: 0.2 – 0.8       0.5 – 1.5
0 -6 km SHEAR: 50 kts – 60 kts                   30 kts – 40 kts
EFF. SHEAR: 40 kts – 50 kts                         30 kts – 40 kts
MID LEVEL LAPSE RATE: 6.5C – 7.0C     6.0C – 6.5C
DEWPOINT: 55F – 62F                                     66F – 70F
EHI: 0.6 – 1.3                                                        0.9 – 1.4
TOTAL TOTALS INDEX: 51C                         52C
K INDEX: 31C – 33C                                           27C – 29C
SWEAT INDEX: 375 – 400                              400 – 495
THOMPSON INDEX: 32 – 37                        30 – 34
CRAVEN – BROOKS INDEX: 10,000        10,000 – 25,000

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 and HRRR 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. PDT – 8:00 P.M. PDT

NAM 3KM STP FORECAST 1:00 P.M. PDT – 8:00 P.M. PDT

HRRR 3KM SCP FORECAST 1:00 P.M. PDT – 8:00 P.M. PDT

HRRR 3KM STP FORECAST 1:00 P.M. PDT – 8:00 P.M. PDT

NAM 3KM SCP FORECAST 3:00 P.M. CDT MAR. 26 – 1:00 A.M. CDT MAR. 27

NAM 3KM STP FORECAST 3:00 P.M. CDT MAR. 26 – 1:00 A.M. CDT MAR. 27

HRRR 3KM SCP FORECAST 3:00 P.M. CDT MAR. 26 – 1:00 A.M. CDT MAR. 27

HRRR 3KM STP FORECAST 3:00 P.M. CDT MAR. 26 – 1:00 A.M. CDT MAR. 27

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 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 day!

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