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April 14-17 Severe Prospects


Indystorm

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I think we are close enough now to begin to raise consideration of possible svr in the area from Quincy to Quad Cities to Chicago on Saturday evening and in Illinois and Indiana on Sunday. Obviously strong concerns exist Sat for a plains tornado outbreak at least per European model, but as I look at GFS parameters in today's (Tues) a.m. and afternoon runs I am getting concerned for Illinois.

Temps around 70, dp low 60's, CAPE 1500. low LCL's and minimal CIN, -5 LI, 80-90 knots at 500 mb and 50 knot 850 begin to raise my concerns. Tonight's run and SPC extended outlook Wed. will be very interesting.

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I think we are close enough now to begin to raise consideration of possible svr in the area from Quincy to Quad Cities to Chicago on Saturday evening and in Illinois and Indiana on Sunday. Obviously strong concerns exist Sat for a plains tornado outbreak at least per European model, but as I look at GFS parameters in today's (Tues) a.m. and afternoon runs I am getting concerned for Illinois.

Temps around 70, dp low 60's, CAPE 1500. low LCL's and minimal CIN, -5 LI, 80-90 knots at 500 mb and 50 knot 850 begin to raise my concerns. Tonight's run and SPC extended outlook Wed. will be very interesting.

Warm front might produce in a big way for IL/WI on Saturday. Early to tell specifics but boy does it need to be watched.

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I'm supposed to be at Skilling's seminar on Saturday...

I have 3 choices on Saturday, paintball, FermiLab, or chasing with a coworker. Having never gone storm chasing before, leaning toward that, but wondering if we'll get called into work on a day off if the threat is close enough to the LOT cwa.

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From the Central/Western forum regarding the early weekend threat.

Here is an overlay I have of 0-4 km theta-e lapse rates and 300 mb jet speed. Generally speaking the overlap in the two is good for severe weather.

This is the 11/06z GFS run, and it is the first to really show the overlap along the warm front in Iowa into Illinois. Between 70 and 90 knots on the southern fringe of the main jet core over the top of -4 to -5 deg/km would be more than sufficient for warm frontal action.

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12z GFS looks pretty good in warm frontal zone into northern IL, LI's below -5 in NW IL, CAPE over 1000 J/kg, more than sufficient deep layer and low level shear, nice backing of winds from 850 down to surface. http://beta.wxcaster.com/cgi-bin/parse_skewt_trace_all.cgi?model=GFS&STATIONID=KMLI. Really impressive hodograph at hour 84 at Moline, and a lot of the parameters on the sounding look good, though the warm nose at 750 mb and the lack of low level CAPE could be problematic. Sunday looks interesting for severe prospects along the warm front as well on the 12z GFS.

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FRIDAY THROUGH SUNDAY...EPISODES OF SHOWERS AND EMBEDDED NON-SEVERE

THUNDERSTORMS SUGGESTED ATTM WITH SLOW MOVING FRONT AND SEVERAL SHORT

WAVES MOVING ALONG AND AHEAD OF THIS BOUNDARY AS LARGE UPPER LOW

MOVES EAST NORTHEAST INTO AREA FROM SW CONUS. HIGHS MOSTLY IN THE

60S ON FRIDAY AND 65 TO 75 ON SATURDAY AND SUNDAY. ORGANIZED AREAS

OF SHRA AND SOME TSRA TO RESULT IN DAILY MOSTLY MODERATE RAIN TOTALS.

BEST CHANCE OF HEAVIEST RAINS MAY OCCUR SUNDAY WITH SURFACE LOW

ARRIVING FROM WEST WITH GREATEST FORCING. MINS IN THE 50S TO NEAR 60

DEGREES IN THE SOUTH. POPS...MOSTLY IN THE LIKELY CATEGORY OF 60-70

PERCENT ATTM AS TIMING A LINGERING QUESTION. PW VALUES OF ~1 UP TO

1.5 INCHES SUGGESTED FOR MODERATE TO LOWER END HEAVY RAIN AMOUNTS

EACH DAY UNTIL FRONT PASSES.

KDVN afd this afternoon stresses heavy rain threat over the weekend and non severe t storms. Not sure I agree with that.

Quad City sounding for Sat. evening posted in the central/west thread is rather ominous.

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I am becoming increasingly concerned for my area around Saturday/Sunday [Kankakee IL/KVAA area]...some impressive shear and low LCL's. The problem will be, for fans of severe weather, the CAPE. It's hard to predict about 3/4 days out but I am watching intently.

Welcome to the board! I find this forum very helpful and informative for svr weather and winter storm discussions especially. With a scenario as complex and widespread geographically as this one is with multiple day concerns we will have to take it one day at a time since boundaries and mesoscale features won't be known almost till nowcasting time.

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Welcome to the board! I find this forum very helpful and informative for svr weather and winter storm discussions especially. With a scenario as complex and widespread geographically as this one is with multiple day concerns we will have to take it one day at a time since boundaries and mesoscale features won't be known almost till nowcasting time.

Thank you! And I was thinking about this being a possible nowcasting event. As a survivor of an EF-2 tornado in Richton Park [windows shaking, apartments demolished within walking distance of me, freight train noises] in 2008...tornadoes get me shaken up a bit. But I do like weather forecasting.

Back ON topic, I do find it a bit of a relief that the SPC hasn't had us in risk areas [so far] for days in advance.

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