Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 250452

Area Forecast Discussion
National Weather Service La Crosse WI
1152 PM CDT Mon Apr 24 2017

.SHORT TERM...(Tonight through Wednesday)
Issued at 230 PM CDT Mon Apr 24 2017

Currently, upper level shortwave driving areas of mostly light
showers across MN at mid afternoon. Meso models suggest some of
these showers could work across the local area later this afternoon-
tonight. Awfully dry sfc/near sfc air though - per obs and bufkit
soundings. Rain is going to have a hard time winning out against the
dry air - especially light rain. Going to keep the forecast dry for
now and will monitor.

That said, rain looking likely for most of the region over the next
couple days, although locally the area could be spared the heavier
rainfall (a good thing considering the already soggy grounds and
high running rivers).

Piece of upper level energy kicking out of a 500 mb trough over the
southern rockies Tue, lifting northeast across the Upper Mississippi
River Valley Tue afternoon/night. The shortwave will give a sfc cold
front a bit of a push east, more or less running north-south along
the mississippi by 06z wed. Some low level warm air advection with
the upper level wave with some additional lift suggested by the left
exit region of a 300 mb jet streak. The bulk of the saturation lies
along and west of the cold front though, where the best lift is also
expected. Modeled QPF follows, with the greater amounts progged over
MN into northwest WI.

The mean 500 mb trough slides east Wed, with the axis into the local
area Thu morning. The cold front stays ahead of the trough, moving
across mich by this time. Decent frontogenetic forcing with the
boundary - especially by Wed night as shortwave energy lifts
northeast with the upper level trough. Right entrance region of
another 300 mb jet streak will also lend a hand in the lift Wed
night. The favored rain (and qpf) area will coincide with this mix
of lifting mechanisms, with the models favoring far eastern IA/Ill
into eastern WI.

Fairly confident that the entire area will see some rain Tue-Wed.
Model trends though pointing to keeping the heavier rains just west
and east.

Thunder risk looks low/none. What minor CAPE indicated in the
GFS/NAM for Tue night lies outside of the higher rain threat - far
northeast IA/southwest WI. Instability axis shifts east on Wed. Will
hold onto those small chances across the south Tue night for now.

.LONG TERM...(Thursday through Monday)
Issued at 230 PM CDT Mon Apr 24 2017

Fairly active, wet weekend in store for the region, although the
details and timing for the best pcpn chances is unclear with
differences between the GFS and EC continuing. Pieces of upper level
shortwave energy move northeast out of a deepening 500 mb trough
over the desert southwest, with that trough/closed 500 mb low
eventually lifting across the region sun-mon. Bands of pcpn result.
Despite the differing opinions in the models, they both agree on
periods of rain from Friday night through Sunday - potentially into
Monday. Going to let consensus solution dictate rain chances for now.

The clouds and pcpn will keep temps cool...with highs mostly in the
50s. At this time doesn/t look cold enough to warrant any mixed pcpn


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1152 PM CDT Mon Apr 24 2017

A cold front extended from central Minnesota into eastern Nebraska
late this evening. This front will continue to move slowly east
through Tuesday evening and is expected to reach western Wisconsin
and eastern Iowa. Moisture will continue to return to the region
ahead of the cold front which will allow for the ceilings to
gradually come down during the day Tuesday, but should remain VFR.
The 24.00Z NAM and the meso-scale models continue to show almost
all the rain remaining behind the front Tuesday closer to the
upper level low and short wave trough that will be back across the
Dakotas. The exception to the this looks to be a wing of showers
that works from south to north across the area from late morning
into the middle of the afternoon that could bring a couple hours
of rain to KRST. As the upper level low and short wave trough
catch up with the front Tuesday evening, the showers should then
become more widespread and start to move out ahead of the front as
well. As this occurs, the ceilings should go down to MVFR for both
airports with some reductions to the visibility also possible.




LONG TERM....Rieck
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