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(T. F. “Storm” Walsh III)
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The Storm Prediction Center (SPC) has designated a SLIGHT risk of Severe Thunderstorms for Friday, Mar. 16, 2018 ACROSS PARTS OF NORTHERN LOUISIANA…ARKANSAS…MISSISSIPPI AND WESTERN TENNESSEE in the day 2 Convective Outlook…
There is a MARGINAL risk ACROSS PARTS OF LOWER TO MID MISSISSIPPI VALLEY…ARKLATEX…TENNESSEE VALLEY…AND LOWER MISSOURI VALLEY…
Scattered severe thunderstorms are possible across parts of the lower to mid Mississippi Valley including the threat of large hail, damaging winds, and perhaps a few tornadoes.
Based on my afternoon analysis of forecast sounding data from F5 DATA, utilizing the NAM-WRF solution (as SPC in their report referenced the NAM model), severe indices and parameters suggest the bulk, or main portion of the severe thunderstorms, should occur approximately within the time frame of 4:00 p.m. to 7:00 p.m. CDT. As time works into later in the evening, conditions begin to weaken, however some weaker, isolated severe incidents could linger into 10:00 p.m.CDT over the eastern portion of the SPC day 2 outlook slight risk outline. There is a discrepancy however, in that the SPC outline, and information in the NAM 12Z analysis differ as far as the outline, based on analysis of various severe weather and tornado parameters, in that the current information presented by the NAM model suggests the outline for the best probability of severe thunderstorms lies further south and west. Regardless, it may be a wise choice to “blend” the outlines to err on the side of safety.
Based on forecast sounding data, upon initiation of the severe activity, supercell thunderstorms are most probable. As evening progresses (mainly around or after 7:00 p.m. CDT), forecast sounding indices weaken, and thunderstorm activity should become more multi cell in nature. Isolated large hail and damaging thunderstorm winds appear to be the main threats, however based on various forecast tornado indices, a few tornadoes are not out of the question. Based on my analysis of the data at hand, I am not expecting any strong, long track tornadoes to develop. Keep in mind, regarding the NAM outlines, and forecast sounding data, these parameters could change by tomorrow morning, and the outlines and severe threats could change slightly.
Based on observed forecast sounding indices, the NAM-WRF suggests the BEST probability for severe weather to occur is in the following outline:
NAM-WRF 12 RUN
Based on various tornado parameters in the forecast sounding data, the NAM-WRF model indicates the best probability for tornado activity to lie within the following outlines:
NAM-WRF 4:00 P.M. CDT
NAM-WRF 7:00 P.M. EDT
Strangely enough, the NAM tornado probability areas pretty well match up with the STP (Significant Tornado Parameter) forecast from the SPC SREF model, noted by the black outline inside the red dashed outline.
SREF STP FORECAST
I have to work tomorrow and Saturday, so I will not be in the office to update you.
Residents within the risk areas should monitor NOAA Weather Radio and NWS statements throughout tomorrow.
IF A TORNADO WARNING IS ISSUED FOR YOUR AREA, SEEK SAFE, STURDY SHELTER IMMEDIATELY!
Please use the following linked maps for updated severe weather and Doppler Radar information.
SPC also indicates a MARGINAL risk for Saturday, and a probability for severe weather on Sunday.
Have a blessed evening!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS