Area Forecast Discussion
Issued by NWS La Crosse, WI

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931
FXUS63 KARX 211110
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
610 AM CDT THU JUL 21 2016

.SHORT TERM...(Today through Friday)
Issued at 336 AM CDT Thu Jul 21 2016

Problems galore in the short term today. Models have done a terrible
job of depicting the convective potential with this obvious QLCS
squall line moving through MN. Even with convection ongoing across
ND near the 00z init time of the models, most had no clue. But the
positive side of things...the action is going on in the best areas
as diagnosed via conventional mass field analysis. As such, do
anticipate that the ongoing convection will continue southeast
through the northern third of the forecast area this morning, which
was not accounted for in the previous forecast. The rain cooled air,
clouds, and resultant cold pool will throw a huge monkey wrench into
the heat forecast. Still feel there will be a chance for the
atmosphere to recover, and it will still get pretty warm. And the
rain may even add more low level moisture to the equation. But the
cold pool may take some time to overcome, so our actual air
temperature may not end up quite as warm as previously forecast. In
fact, our going temps were 2-7 degrees above the warmest of the
guidance values. So did lower temperatures some. The resulting heat
index values did come down some as well, and some areas may not hit
the actual Excessive Heat Warning criteria. But it will be close,
and will likely still be well into Advisory range. So will just hold
on to the headlines as they are at this point.

Adding further to the story...the few model solutions that actually
have some convection are suggesting that this line may run all the
way down into southern WI and eastern IA. Perusal of other model
fields suggests there should be a lull in the action for a time this
afternoon, so will continue to hold onto that idea. Which also
allows me to keep the rest of the forecast somewhat intact. But if
that actually does happen, temps/sky and the heat headlines are all
in trouble.

This all dovetails into tonight and even Friday as well. Based on
the convection and the strength of the short wave trough that is
causing all of this as it moves into the western Great Lakes, the
surface front is now shown to be down into Iowa by the models. Some
depict more convection along it. If that indeed is where the front
ends up, and we get more rain, we probably are too high for temps
tonight into Friday as well. Lots for the day crew forecasters to
look at, with several significant changes perhaps needed.

.LONG TERM...(Friday night through Wednesday)
Issued at 336 AM CDT Thu Jul 21 2016

The front is expected to lift north again Friday night in advance of
the next short wave that will send a surface low and cold front
through the region for the weekend. Indications are that some
convection will fire along this boundary, but it may be south and
west of the forecast area. The best chance for storms will come
Saturday afternoon and night. There will be a severe risk with these
storms due to ample shear and instability.

A brief respite Monday before another disturbance spreads showers
and thunderstorms into the region for late Tuesday into Wednesday.
Not much time to really dig into this given all of the short term
concerns.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 610 AM CDT Thu Jul 21 2016

Primary concern for aviation interests today is the convective
potential this morning. Good squall line passing across northern
WI, but it appears it will stay north of both airfields. But those
who want to fly north or east this morning will have some
circumnavigation to deal with. Outside of this, expect warm and
muggy conditions once again today. Various short term models
suggest a cold front will drop into the region by evening, so
there could be some isolated convection that forms during the
evening. But the chances appear so small at this point that it
doesn`t even warrant mention. But will definitely have to monitor
trends later today.

&&

.ARX Watches/Warnings/Advisories...
WI...Excessive Heat Warning from noon today to 7 PM CDT Friday for
     WIZ032>034-041>044-053>055-061.

     Excessive Heat Warning from noon today to 10 PM CDT this evening
     for WIZ017-029.

MN...Excessive Heat Warning from noon today to 7 PM CDT Friday for
     MNZ079-086>088-094>096.

IA...Excessive Heat Warning from noon today to 7 PM CDT Friday for
     IAZ008>011-018-019-029-030.

&&

$$

SHORT TERM...MW
LONG TERM...MW
AVIATION...MW



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