Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 202342

Area Forecast Discussion
National Weather Service La Crosse WI
642 PM CDT Thu Apr 20 2017

.SHORT TERM...(This evening through Friday)
Issued at 318 PM CDT Thu Apr 20 2017

At 3 PM, a trough was located across central Wisconsin and
central Minnesota. The combination of this trough and 950 to
900 mb lapse rates greater than 8 C/km kept instability showers
going across central Wisconsin. In addition, cloudy skies (due to
the cyclonic flow aloft) only allowed temperatures to range from
the mid 40s to lower 50s.

For tonight and Friday morning, cyclonic flow aloft will keep
skies mostly cloudy across western Wisconsin and for the counties
along the Mississippi River in southeast Minnesota and northeast
Iowa. With 900 to 950 mb lapse remaining greater than 8 C/km,
expect scattered instability showers to continue through 10 PM in
central and north-central Wisconsin. The combination of this
cloud cover and northwest winds around 10 knots will limit the
cooling and frost potential tonight. Low temperatures on Friday
morning will be in the mid and upper 30s.

On Friday afternoon, skies will become sunny across the region.
High temperatures will range from the mid 50s to lower 60s. Some
MOS guidance even suggests the potential for some mid 60s in the
Mississippi River Valley.

.LONG TERM...(Friday night through Thursday)
Issued at 318 PM CDT Thu Apr 20 2017

From Friday night into Saturday, high pressure will provide mainly
clear skies. As the high drifts overhead on Friday night, the
winds will become light and variable. This in combination with dry
dew points will allow temperatures to fall into mid and upper 20s
in central Wisconsin and in the lower and mid 30s across the
remainder of the forecast area. At this time, the only susceptible
vegetation to freezing temperatures are located along the
Mississippi and Wisconsin river valleys. Fortunately, temperatures
in these areas will be mainly in the mid-30s, so at this time
only expecting some scattered frost.

On Saturday night and Sunday morning, a Canadian cold front will
move south through central Minnesota and central Wisconsin.
Soundings show that much of the lift with this system will go into
saturation and not into generating precipitation. As a result,
only expecting some clouds with this front.

On Sunday afternoon and night, this front will then lift north as
a warm front. With there only being a shallow moisture, no
precipitation is expected.

A series of short wave troughs will then move through the region
on Monday night and Wednesday. Like the past couple of days, the
CAPE is rather limited, so only expecting some showers from it.
The GFS soundings would support the potential of snow showers in
southeast Minnesota and north of Interstate 94 in Wisconsin on
Tuesday night and Wednesday


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 642 PM CDT Thu Apr 20 2017

An area of low pressure was over lower Michigan late this
afternoon with a trough of low pressure extending back to the
northwest across northern Wisconsin. A large area of low level
cyclonic flow was in place around these two features with lots of
clouds in this pattern extending well back into the Dakotas. As
the night progresses, the cyclonic flow should relax as high
pressure builds in from the northwest, so the main concern becomes
when will the clouds break up. Given the large extent of the
clouds currently, have played this on the pessimistic side and
kept the MVFR ceilings in place well into the overnight hours at
KRST and until early Friday morning at KLSE. Once the clouds break
up, VFR conditions then expected for the rest of the period as the
high builds in over the region.


.HYDROLOGY...through Monday
Issued at 318 PM CDT Thu Apr 20 2017

Dry weather through Monday will allow the minor flooding along the
Yellow, Black, and Trempealeau rivers to slowly recede.




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