Area Forecast Discussion
Issued by NWS La Crosse, WI

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658
FXUS63 KARX 162358
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
658 PM CDT Wed Aug 16 2017

.SHORT TERM...(Tonight through Thursday Night)
Issued at 152 PM CDT Wed Aug 16 2017

GOES water vapor has an impressive/vigorous mid-level low churning
through western Nebraska. At the surface, a deepening area of low
pressure was moving northeast into northwest IA/southwest MN. Radar
showed numerous showers and embedded thunderstorms pushing northeast
ahead of the low across portions of central MN into central IA.
Otherwise, a fairly nice day across our forecast area with
temperatures in the middle 70s to the lower 80s.

For this afternoon into this evening, looking for that low to
continue deepening over southern MN as the attendant cold front
swings northeast toward the area. RAP/NAM build MUCAPE into the 1000-
2000J/kg range with 0-3km bulk shear of 25-35kt and 0-1km bulk shear
20-25kt. So, there is a small chance of a few strong to severe
storms occurring from late this afternoon into this evening. The main
threat would be gusty winds and hail. Another facet of this storm
system is the amount of precipitable water it pulls into the area.
1.5 to 2.0 inches is indicated by the NAM/RAP through this evening.
So, this means that any storm will be capable of torrential
downpours and perhaps some localized ponding of water. Widespread
flooding is not expected due to the progressive nature of this storm
system.

Breezy/cooler/mostly cloudy conditions will be experienced Thursday
along with scattered showers on the backside of the departing low.
Removed most of the thunder from the area except across north
central WI where steeper lapse rates will exist. Otherwise, plan on
highs in the 70s with those breezy west winds of 15 to 25 mph.

Scattered showers will slowly come to an end Thursday night as the
low pulls northeast into southern Ontario Canada. Look for lows in
the 50s.

.LONG TERM...(Friday through Wednesday)
Issued at 152 PM CDT Wed Aug 16 2017

Will be watching a weak mid-level trough drop through the region
Friday into Friday night for a chance of showers/isolated storms.
Looks dry then for the weekend as a weak ridge of high pressure
drifts across the region. Plan on highs in the upper 70s to the
middle 80s.

A chance of showers and isolated thunderstorms returns for Sunday
night through Tuesday as another trough drops southeast across the
region.

Wednesday looks dry with slightly cooler than normal as Canadian
high pressure sinks southward into the Upper Mississippi River Valley
Region.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 659 PM CDT Wed Aug 16 2017

Not much change was made to the updated 00Z TAFs. A period of RA
and isolated TSRA will be around the TAFs for the next hours, but
then the activity should push northeast. As an area of low
pressure moves east from MN>WI overnight, low clouds will move in
from the west and these are likely to be in the IFR or lower MVFR
range. Some SHRA may accompany these in the morning as northwest
winds kick in.

Refinement to CIGS and VSBYS for the 09Z+ TAF period will occur
in the next TAF issuance /06Z/ when a bit higher confidence on
the outcome can be harnessed.
&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...DAS
LONG TERM...DAS
AVIATION...Baumgardt



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