Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 191110

Area Forecast Discussion
National Weather Service La Crosse WI
610 AM CDT Sun Mar 19 2017

.SHORT TERM...(Today and tonight)
Issued at 225 AM CDT Sun Mar 19 2017

Main forecast concerns today are on whether any showers or isolated
thunderstorms will develop this afternoon into this evening and
breezy southerly winds late this morning through around mid

High pressure exits the region today as a cold front and
shortwave approach from the Northern Plains. A tight pressure
gradient develops across the area today ahead of the front. Plan
on southerly winds of 15 to 20 mph with gusts to around 30 mph at
times in open areas. The cold front then slides in mid afternoon
through mid evening possibly bringing some showers or perhaps
isolated thunderstorms to the area. Atmospheric moisture is a
problem with this feature and there isn`t much to work with. 850
mb moisture transport noses into the area from the west this
afternoon and if we are going to see any shower activity it should
be developing along this feature. Forecast models really struggle
to saturate and the shortwave moving through is pretty weak.
Looking at the NAM and RAP forecast soundings across the area an
air parcel would have to be lifted from around 800 mb to get any
convection/thunderstorms to develop. With only weak forcing moving
through it probably won`t be enough for thunderstorms to develop
but cannot rule it out. Will confine thunderstorms changes to
portions of northeast Iowa and far southwest Wisconsin where
stronger moisture transport is in place this evening and some
mesoscale models are also developing convection in this area.
There is a better signal in the mesoscale models for the
thunderstorms to develop just south of the area. Will have to keep
a close eye on moisture return today, especially in the 850 to
800 mb level. If its stronger, a line of showers and embedded
thunderstorms would move through the area. Any showers and storms
that develop should quickly exit the area by mid to late evening.

.LONG TERM...(Monday through Saturday)
Issued at 225 AM CDT Sun Mar 19 2017

Dry high pressure builds into the region Monday through Wednesday
with dry weather expected with the potential for some lower
relative humidity values at times possibly leading to fire weather
concerns. See Fire Weather Discussion for details. A fast moving
shortwave just clips northeast Iowa and far southwest Wisconsin
late Monday night into Tuesday possibly bringing some light rain
or snow to northeast Iowa. Will keep a low precipitation chance
over this area but if model trend further south, this will not be

The high departs the region late Wednesday as a deep trough develops
over the southwest conus and lifts northeast towards the Upper
Mississippi River Valley. The first wave of precipitation looks to
arrive late Wednesday night into Thursday morning and with some
colder air near the surface and a warm layer aloft, we could see
some mixed precipitation type concerns across portion of central
into north-central Wisconsin. Confidence wasn`t high enough to
include exact details on precipitation types but will have to keep a
close eye on this timeframe. Precipitation chances continue through
Saturday as the low looks to continue impacting the region.
Depending on the low track, we may see some precipitation type
concerns again.  The the Thursday-Saturday timeframe will be a
period that bears close watching the next few days.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
night) Issued at 610 AM CDT Sun Mar 19 2017

High pressure over eastern WI early this morning will continue to
move east today, with a tighter pressure gradient and S-SE low level
flow increasing across the area. Brisk S/SE winds (14-20kt G22-28kt)
expected by late morning thru mid afternoon. Winds decrease a bit by
later afternoon with approach of a weak sfc trough/front across MN.
Moisture also increases ahead of this front, as some weak energy
aloft would be approaching. By late afternoon and for the early
evening hours, higher-based widely sct -SHRA are possible, with most
of the moisture/instability and lift above 850mb. Included a VCSH
mention at both KRST/KLSE for now, roughly 21z-02z. The sfc trough/
front to pass during the overnight hours, with winds becoming NW to
N toward the end of the taf period. May yet be a little BR behind
the passing trough/front late tonight, but the high pressure coming
in behind the front is quite dry in the lower levels with subsidence
and anti-cyclonic flow, so left conditions VFR into Mon morning.


.FIRE WEATHER...Monday through Wednesday
Issued at 225 AM CDT Sun Mar 19 2017

Dry Canadian high pressure builds into the region Monday through
Wednesday bringing low relative humidity values to the area. Winds
look to be fairly light through this period so not expecting Red
Flag conditions at this time. Monday: Areas north of Interstate 90
across much of western into northern Wisconsin will have the lowest
relative humidity values in the 20 to 30 percent range. Tuesday:
Much of western into central Wisconsin will see afternoon relative
humidity values fall into the 20 to 30 percent range again. It`s
possible they will go even lower across central Wisconsin. Tuesday
will have a little more wind to contend with. Expect northwest winds
of 12 to 13 mph with gusts up to 20 mph possible during peak
heating. Wednesday looks to have the lowest relative humidity
values, ranging from 20 to 30 percent for areas along and east of
the Mississippi River, including central Wisconsin. Again central
Wisconsin could see values drop into the teens. Winds will be fairly
light on Wednesday as the high settles overhead.




SHORT TERM.....Wetenkamp
LONG TERM......Wetenkamp
FIRE WEATHER...Wetenkamp is the U.S. government's official web portal to all federal, state and local government web resources and services.