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April 2nd - April 5th Severe Weather


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When I see grammatical and other lanuguage mistakes in NWS AFD discussions of svr wx it tells me that the author is getting nervous about the situation. Have seen this on other occasions for an interesting psychological twist.

It was probably just a bad mistake. I have made many myself. In a hurry and need to get products out--unfortunately spell check doesn't correct for improperly used words.

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SOUTHWEST WINDS CONTINUE TO ADVECT WARM MOIST UNSTABLE AIR INTO EASTERN KANSAS...WHILE DRIER AIR IMPACTS NORTH CENTRAL KANSAS WHERE RED FLAG WARNING WILL BE ISSUED. SOME AGREEMENT IN INITIATING CONVECTION RIGHT AROUND THE 0Z HOUR ACROSS EAST CENTRAL AND NORTHEAST KANSAS...AND WITH CAPE VALUES 2000+ J/KG AND SUCH STRONG WINDS IN THE COLUMN EXPECT PRIMARILY A HAIL AND WIND THREAT FROM SEVERE STORMS THAT DEVELOP. TURNING OF THE WINDS IN THE LOW LEVELS NOT AS CONDUCIVE TO TORNADIC DEVELOPMENT...BUT WITH GOOD AMOUNT OF CAPE IN THE LOWER 2KM AND AN INCOMING BOUNDARY IT REMAINS A CONCERN TO BE MONITORED.

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CLE

THE MODELS ARE FINALLY LOOKING MORE IN AGREEMENT ON MONDAY WITH THE

TIMING OF THE FRONT....WHICH SHOULD CROSS NORTHWEST OHIO DURING THE

MIDDAY HOURS AND BE EAST OF THE FORECAST AREA BY EVENING. TIMING IS

EVERYTHING AS TOO HOW UNSTABLE IT CAN GET AND HOW WARM IT CAN GET.

WE COULD GET TO 70F BUT THE FRONT IS A LITTLE FASTER THAN I WOULD

LIKE TO SEE FOR MAXIMUM HEATING. WILL STICK WITH A FORECAST

GENERALLY IN THE MID 60S FOR HIGHS. I SUSPECT THE SEVERE WEATHER

THREAT WILL DEPEND A LOT ON THE AMOUNT AND COVERAGE OF THE SHOWERS

AHEAD OF THE FRONT. THERE SHOULD BE PLENTY OF JET/DYNAMIC FORCING

AND SHEAR BUT THE INSTABILITY MAY BE HARD TO MAXIMIZE. THERE IS THE

POTENTIAL FOR A BIG SEVERE WEATHER DAY BUT IT IS TOO EARLY TO TELL.

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Low level shear looks much better to me on the GFS compared to the NAM, but the GFS has less instability. The GFS has a tendency to underdo instability though. If we can match the wind fields from the GFS to the instability of the NAM then we may really have some fun.

Here's a GFS sounding for near Princeton Illinois late tomorrow.

GFS_3_2011040218_F30_41.5000N_89.5000W.png

GFS_3_2011040218_F30_41.5000N_89.5000W_HODO_SM.png

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If we take this run seriously, the cap could be broken as far south as nrn or ctrl OK. Isolated storms could yield some great structure shots for chasers.

Noticed that in the CINH plots. I can't say I can remember a good chase day in April with such a sheared-out, positive-tilt trough, but if a storm does somehow initiate and sustain itself around sunset in the pre-dryline environment, I imagine impacts will be significant.

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I gotta give SPC props...I was doubtful last night when they were hitting the tornado threat but it appears to be very real.

Oh it's real alright...something gets going along that warm front rooted near the sfc and there will be hell to pay...I'm still not 100% sold on it happening though...

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I know Janet/Janet earlier posted a caution about dewpoints verifying on the models...and with these early spring systems moisture return is historically a problem, but with the wind advisories over such a large area at present for tomorrow they might just advect north and add fuel to the fire as the models are predicting.

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I know Janet/Janet earlier posted a caution about dewpoints verifying on the models...and with these early spring systems moisture return is historically a problem, but with the wind advisories over such a large area at present for tomorrow they might just advect north and add fuel to the fire as the models are predicting.

I actually tend to think WAA is underdone most of the time.

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Oh it's real alright...something gets going along that warm front rooted near the sfc and there will be hell to pay...I'm still not 100% sold on it happening though...

I guess the big question is how strong the cap will be. Hodos look good so whatever can root near the surface might cause problems.

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I know Janet/Janet earlier posted a caution about dewpoints verifying on the models...and with these early spring systems moisture return is historically a problem, but with the wind advisories over such a large area at present for tomorrow they might just advect north and add fuel to the fire as the models are predicting.

Actually its just the opposite - since the flow in the lower levels is so veered, they are downsloping and dry. As such, the winds could in fact advect dry, not moist air across the warm sector. With such strong solar insolation progged tomorrow, that dry air would mix down to the surface, raise LCL's, and increase inhibition.

The 0Z NAM is so different in that it moistens things up a little in the low levels and thus the sfc, and weakens the EML ever-so-slightly compared to prior runs. Having moisture NOT mix out south of the IA-MO border would boost convective chances south of that area, and in fact we see NAM break out precip near KC.

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It's definitely gonna have to be some pretty impressive moisture advection tomorrow to get those 60+ dews north. Just 12-15hrs before the event the NAM shows north-central Illinois with dews in the mid to upper 20s lol.

EDIT: Just 6hrs after this the same areas are shown to have dews in the low to mid 50s. Wow.

EDIT2: We go from a dewpoint around 28 at 7am, to near 65 by 4pm.

NAM_221_2011040300_F12_DPTF_2_M_ABOVE_GROUND.png

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It's definitely gonna have to be some pretty impressive moisture advection tomorrow to get those 60+ dews north. Just 12-15hrs before the event the NAM shows north-central Illinois with dews in the mid to upper 20s lol.

EDIT: Just 6hrs after this the same areas are shown to have dews in the low to mid 50s. Wow.

NAM_221_2011040300_F12_DPTF_2_M_ABOVE_GROUND.png

A general rule is that it takes at least 24 hours for 60 degree dewpoints in Louisiana to make it up to Indiana. In this case we have 60 dews progged in OK/AR at 12z...can they make it into northern Illinois by evening?

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A general rule is that it takes at least 24 hours for 60 degree dewpoints in Louisiana to make it up to Indiana. In this case we have 60 dews progged in OK/AR at 12z...can they make it into northern Illinois by evening?

Definitely sounds far fetched, but the NAM forecasts winds at 850mb between 70-80kts over a wide swath for much of tomorrow morning. My gut feeling is it's overdone on the moisture return, but I think we'll see dews eventually make it up close to 60 by early evening.

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