Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 250240

Area Forecast Discussion
National Weather Service La Crosse WI
940 PM CDT Sat Jun 24 2017

.SHORT TERM...(Tonight through Sunday Night)
Issued at 150 PM CDT Sat Jun 24 2017

Scattered showers and thunderstorms moving across parts of southeast
MN at this time ahead of a potent mid-level PV-anomaly pushing
southeastward through central MN. Latest RAP shows lobe of 700-300
PV-advection pushing in with this wave and is expected to continue
fueling shower/thunderstorms into early this evening. Will be
watching for a few stronger storms capable of small hail and sub-
severe wind gusts in the 40-50 mph range as RAP also showing decent
30-35kt bulk shear along/south of I-90 with MUCAPE in the 500-
1000J/kg range. Look for a diminishing trend later this evening and
pretty much precipitation-free by midnight with loss of surface
heating and as we get on the subsident side of the passing wave.
Otherwise, rest of tonight looks to be a chilly one with lows
dipping into the mid 40s to near 50.

Another round of scattered showers and isolated thunderstorms
expected to develop by late Sunday morning, lasting into the evening
with lingering cold cyclonic flow aloft. In addition, models bring
another mid-level trough through. Bulk of these showers/isolated
storms expected to be east of the Mississippi River and most
concentrated northeast of I-94, closer to the better mid-level
forcing and steeper lapse rates. Otherwise, plan on significantly
cooler than normal highs Sunday only in the 60s with lows Sunday
night in the middle 40s to near 50.

.LONG TERM...(Monday through Saturday)
Issued at 150 PM CDT Sat Jun 24 2017

Cool cyclonic flow continues through Monday for lingering small-end
shower/isolated thunder chances, mainly east of the Mississippi
River. Look for highs in the 65-70 degree range.

High pressure builds across the region for Monday night through
Tuesday for dry/warmer conditions. Temperatures still look to be
some 5 to 10 degrees below normal, but do not think there will be
any complaints as highs Tuesday top off in the 70s.

Latest GFS/ECMWF in good agreement in pushing an area of low
pressure and cold front into/through the region Tuesday nigh through
Thursday night for the likelihood of showers and thunderstorms. Will
have to keep an eye on the possibility for strong to severe storms
centered on Wednesday. The GFS shows fairly boisterous MUCAPE in the
2000-3800J/kg range while the EC only shows 500-1500J/kg. Plenty of
available Bulk Shear in the 35-45kt range.

Westerlies aloft bring a couple more short wave trough across the
region Friday through Saturday for continued shower/thunder chances.
Otherwise, no big warm-ups on the horizon with fairly high-zonal
flow. Looks like highs in the middle 70s to lower 80s Thursday and
in the 70s Friday/Saturday.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 940 PM CDT Sat Jun 24 2017

Cigs: Modeled RH fields and current satellite imagery show an area
of mvfr/vfr cigs sinking southeast across nd/northern MN - with the
models bringing it across the TAF sites by 12z Sun (or so). Should
get a little diurnal bump as Sunday wears on, and likely scattering
out Sunday evening.

WX/vsby: Another round of shra/ts similar to today for Sunday, as a
shortwave/favorable low level lapse rates/instability work on the
available moisture. Perhaps a bit better chances east of the
Mississippi river. Main threat time would be from 19-00z.

See some threat for valley fog at KLSE for the first part of the
overnight tonight - especially if winds remain decoupled. Clouds
coming in from the north and 10 kts or greater winds just off the
deck will be limiting factor. Shallow? Will leave P6SM for the
moment, but trends will monitored.

Wind: west northwest through Sunday. Will stay up mostly tonight,
although could stay decoupled at KLSE until sunrise, then increase
some on Sunday. Expect some gustiness by late morning, with again
enhanced gusts around any stronger shower/storm.




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