Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 160448

Area Forecast Discussion
National Weather Service La Crosse WI
1148 PM CDT Sat Oct 15 2016

Issued at 534 PM CDT Sat Oct 15 2016

Forecast updated to reduce precipitation chances across much of
the area. Latest indications are that any isolated showers would
mainly be confined to portions of northeast Iowa and extreme
southwest Wisconsin. While some pockets of drizzle cannot be ruled
out elsewhere, most of the area will see little or no rain for
the rest of the evening hours. Latest mesoscale models indicated
showers and storms will develop late tonight but will be just
southeast of the forecast area across portions of eastern Iowa
through southeast Wisconsin. The potential remains for some dense
fog late tonight into Sunday morning for areas where skies clear.
Will continue to monitor cloud trends closely for the evening into
the overnight.


.SHORT TERM...(Tonight through Sunday Night)
Issued at 227 PM CDT Sat Oct 15 2016

Surface map has deep low pressure over western Ontario with a cold
front trailing south-southwestward through central MN. Very moist
southerly flow in advance of this cold front was producing
widespread stratus and areas of drizzle across the forecast area.
This southerly flow was also producing mild temperatures with
readings at 2 pm in the 60s.

Look for the cold front to slip southeast through the area this
evening...then more or less stalling out across northern IL into
southern IA overnight. 0-3km mucape fairly limited in the 400-
800J/kg range with bulk shear decreasing from 25-35kt at 00z to 20-
25kt by 06z. 850mb moisture transport also bends over into northern
IL/southeast WI. Based on this...threat of stronger thunderstorms is
very limited. Otherwise, expecting scattered showers/few storms
ahead of the cold front this evening as it comes through with
overnight lows ranging from the upper 40s across northern WI to the
lower 60s across far northeast IA/southwest WI. Could see some fog
development as well toward morning, especially where breaks occur in
cloud cover.

Skies will range from partly sunny north of I-94 to mostly cloudy
south on Sunday with highs topping off in the upper 60s to the
middle 70s.

Shower and thunderstorms become likely Sunday night as another wave
of low pressure moving across the Northern Plains pulls a warm front
into the area. Increasing 850mb moisture transport/isentropic lift
over this frontal boundary expected to focus shower/storm activity
mainly along/north of I-90. There will also be a marginal severe
threat as elevated mucape increases into the 1500-2500J/kg range
with 0-3km bulk shear in the 30-40kt range. Appears a few strong to
severe storms with large hail would be the main threat. Otherwise,
with warm air advection overnight, lows in the 60s will be some 20-
25 degrees above normal with a few new record warm lows possible.
See climate section below for details.

.LONG TERM...(Monday through Friday)
Issued at 227 PM CDT Sat Oct 15 2016

For Monday through Tuesday...

Main impact will be shower and thunderstorm chances continuing
Monday into Monday night as low pressure and a cold front push
through the area. Will have to keep an eye on a few stronger storms
on Monday with cape pooling along the frontal boundary and decent 0-
3km bulk shear values around 40kt. Otherwise...rather warm
temperatures expected Monday with highs well into the 70s.  Cooler
day Tuesday behind departing low and cold front. Look for highs
dropping into the 60s.

For Wednesday night through Saturday...

Good model agreement and consistency of a longwave trough amplifying
to the west and moving into the area by Thursday. As the trough
moves in temperatures will begin to cool to more seasonable values
with highs in the 50s. Models then diverge on Friday with the 15.12Z
GFS consistently cutting off a low somewhere in the southern CONUS,
though exact location has been changing run to run, and the 15.00Z
ECMWF sliding the trough through rather quickly. The 15.12Z ECMWF is
a bit more in line with the GFS as far as moving the trough through,
though does not completely cut off the low. The 15.12Z runs of the
GFS and ECMWF keep the area mainly dry through the period, though
this could change as future model runs get a better handle on if and
where the low cuts off.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1148 PM CDT Sat Oct 15 2016

MVFR conditions are possible for the overnight in stratus and BR.
If skies go completely clear, we may see some dense fog at the TAF
sites later tonight into early Sunday morning. Otherwise, VFR
conditions return by mid morning on Sunday. Stratus then moves
back into the TAF sites for Sunday evening with MVFR conditions
expected. Will have to keep an eye on LLWS potential as winds
increase to 30 to 38 kts from 1-2kft.


.CLIMATE...(for Monday October 17)
Issued at 227 PM CDT Sat Oct 15 2016

            Record Highest Low   Year Established   Forecast Low

La Crosse           64                 1994              65
Rochester           62                 1953              64




LONG TERM....DAS/Aegerter
CLIMATE......DAS is the U.S. government's official web portal to all federal, state and local government web resources and services.