Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 222047

Area Forecast Discussion
National Weather Service La Crosse WI
347 PM CDT Wed Mar 22 2017

.SHORT TERM...(This evening through Thursday)
Issued at 345 PM CDT Wed Mar 22 2017

At 3 PM, a 1037 mb surface high was centered over central Lake
Michigan. East and southeast winds on the back side of this high
continues to bring very dry air into the Upper Mississippi River
Valley. Dew points ranged from 5 to 15F. Temperatures ranged from
30 to 35F north of Interstate 94 and 35 to 41F across the
remainder of the area. Meanwhile further west, weak to moderate
800 to 600 mb frontogenesis was producing some a light wintry mix
of precipitation from southwest Minnesota southeast into central

The 22.12z models continue to show that an elevated warm front
will move east across southeast Minnesota and northeast Iowa
late tonight and Thursday morning and across western Wisconsin on
Thursday afternoon. The HRRR continues to show that maybe some
elevated showers may develop across western Wisconsin overnight
ahead of this warm front. However with the low levels (sub-cloud
layer) remaining very dry, this precipitation may not make it to
the ground. As a result, kept the forecast dry for the overnight.

During the day Thursday, BUFKIT soundings show that the air mass
will gradually saturate as moisture surges ahead of an approaching
front from the northwest. This will result in the development of
rain across the region. The highest chances will be during the
afternoon. With very dry air still advecting into the area during
the morning, there may be the potential for a light wintry mix at
the onset. However this looks to be brief and should not cause any

.LONG TERM...(Thursday night through Wednesday)
Issued at 345 PM CDT Wed Mar 22 2017

From Thursday night into Sunday, a slow moving upper level low
will move from the Southern Plains into the Ohio River Valley. A
deformation band of rain on the north side of this low will slowly
move south across the forecast area. This deformation band will be
mainly along and north of Interstate 90 from Thursday night into
Friday night, and along and south of Interstate 90 from Friday
night into Sunday. It continues to look like the much of the
instability will remain south of the forecast area. As a result,
kept the mention of thunder out of the forecasts. Rainfall amounts
from this system will likely range from 1 to 1.5 inches. With this
rain spread out of over a long-period of time, only anticipating
in bank rises on area rivers.

With the potential that the southern part of the forecast area
could enter the warm sector of this system on Friday, the
temperatures forecast is rather tricky. The ECMWF ensemble is
showing standard deviations of 4 to 6. For the time being, just
staying close to the ensemble mean. However with that said there
could be potential for a large bust in the temperature forecast
for areas along and south of Interstate 90.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1233 PM CDT Wed Mar 22 2017

Main taf concerns through the taf period are southerly winds
increasing tonight...then ceilings lowering into MVFR after 12z
Thursday. High pressure over eastern Wisconsin builds east of the
area and allows pressure gradient to tighten across the area late
this afternoon and evening. This will increase the winds to 10 to
15 knots...possibly to around 20 knots after 12z
both RST and LSE taf sites this evening/tonight. With the
southerly winds...low levels of the atmosphere will begin to
saturate after 09z Thursday and ceilings are expected to lower to
MVFR at both RST/LSE taf sites after 14z Thursday. The increasing
moisture will also provide a small chance for light rain mainly
west of the Mississippi river after 15z Thursday...however the
higher chances will occur after 18z Thursday. For now...will leave
mention of light rain out of tafs.


.HYDROLOGY...(Thursday night through Wednesday)
Issued at 345 PM CDT Wed Mar 22 2017

It continue to look like the area will be in a prolong wet period
from Thursday night into Sunday as a thin ribbon of Gulf of Mexico
moisture is brought northward into the region. Precipitable water
values continue to be 2 to 3 standard deviations above normal.
Rainfall totals will likely be in the 1 to 1.5 inch range. However
with this rain spread out of over a long-period of time, only
anticipating in bank rises on area rivers.



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