Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 242350
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
650 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
chances.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 650 PM CDT Mon Apr 24 2017

The cold front over western Minnesota will slide east and is
expected to be eastern Minnesota into western Iowa by late Tuesday
afternoon. A weak area of low pressure should form along the front
Tuesday afternoon over Iowa and move into southern Minnesota by
late in the day. There will be a gradual return of moisture into
the area ahead of these systems, but only look for ceilings to
gradually come down and for the most part staying VFR through the
period. The exception to this may be at KRST where a MVFR ceiling
could move into late Tuesday afternoon if showers develop ahead of
the front. However, this is a low confidence forecast as the
24.18Z NAM and almost all the meso-scale models suggest the
showers will initially be behind the cold front closer to the
upper level low and main short wave trough that will still be back
over the western Dakotas. The winds will diminish this evening as
the low level inversion develops but remain rather strong just
above the inversion. The NAM continues to suggest there will be
enough speed difference for some low level shear at KLSE into the
overnight hours and will maintain this in the forecast.

&&

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

$$

SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...04



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