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(T. F. “Storm” Walsh III)
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Good day everyone!
The Storm Prediction Center (SPC) has designated the following Severe Weather Risk areas in the Day 1 Convective Outlook, as of the 1300Z issuance:
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHERN ILLINOIS AND SOUTHERN WISCONSIN INTO LOWER MICHIGAN…
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EDWARDS PLATEAU (TX) TO THE ARKLATEX THIS AFTERNOON…
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING AND IN BETWEEN THE TWO SLIGHT RISKS…
Scattered severe thunderstorms capable of hail and wind are expected from: * Northern Illinois and southern Wisconsin into Lower Michigan, with damaging winds, hail and perhaps a tornado or two. * Edwards Plateau (Texas) to the Arklatex this afternoon, with large hail and severe gusts possible.
Based on analysis of the SPC outlook, ongoing convection and thunderstorms should weaken by later this morning, over the northern slight risk area. Behind this morning activity, thermodynamics are forecast to to change by this afternoon, which can be read in the outlook. The northern slight risk area over portions of IL., IN., and MI. are forecast to be under the left exit region of a jet max within the jetstream. The following link will explain the significance of the left exit region, regarding a jet max:
Based on the current forecast sounding data from the NAM-WRF 06Z run, residents over the slight risk areas may begin to notice some change in the weather at approximately 1:00 p.m. CDT. However, current sounding data indicates the bulk of, and highest probability for the onset to be approximately 4:00 p.m. CDT, through the early evening hours. Based on forecast indices, hail and damaging thunderstorm gusts appear to be the higher of the probabilities. Earlier in the outlook, SPC had ascertained that thunderstorm activity would most likely be multicell / MCS type setup. However, based on the thermodynamic changes that should occur, some cells have the potential to become supercellular in nature.
Based on current forecast tornado indices and parameters, I do not believe at the present moment we should see anything strong, however keep abreast of the situation via local NWS statements and watches.
The following outlined maps from F5 DATA software from the NAM-WRF forecast soundings, indicated where the highest probability for experiencing severe thunderstorms and accompanying weather should occur, between 3:00 p.m. – 7:00 p.m. CDT:
F5 DATA NAM-WRF 06Z RUN
The following F5 DATA maps indicate where the NAM-WRF believes the highest probability for isolated tornadoes may occur during the same period:
F5 DATA NAM-WRF TORNADO
During the 3:00 -7:00 p.m. CDT time frame, some of the sounding values are forecast to reach the following levels:
Northern risk area:
SBCAPE: 1000 – 2000 j/kg
MLCAPE: 1000 – 1500 j/kg
LIFTED INDEX: -6 to -8
MID LEVEL LAPSE RATE: 8.5 – 9.0 C/km
SBCAPE: 2000 – 3000 j/kg
MLCAPE: 2000 – 2500 j/kg
LIFTED INDEX: -6 to -8
MID LEVEL LAPSE RATE: 8.0 – 8.5 C/km
Residents in the outlined SPC slight risk areas, should closely monitor NOAA Weather Radio, and local NWS statements for up to date information regarding any necessary actions.
IF A TORNADO WARNING IS ISSUED FOR YOUR AREA…SEEK SHELTER IMMEDIATELY!
The following graphics are linked to their respective sites. Mouse over and click on the graphics for up to date information.
Tomorrow, I am going to try and have my 2017 Hurricane Season Activity Forecast issued
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS