Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 201720
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1220 PM CDT Mon Mar 20 2017

.SHORT TERM...(Today and tonight)
Issued at 254 AM CDT Mon Mar 20 2017

Main forecast concerns for today are on slight chances for light
rain showers north of Interstate 90. Drier air moving in may
produce low relative humidity values this afternoon.

Cold front has shifted south and east of the area early this morning
with widespread thunderstorm activity across northern Illinois.
Further north, some light radar returns noted across north
central Wisconsin. These are associated with a weak shortwave
moving through. Another shortwave moves in later this morning into
this afternoon and may generate some isolated to scattered light
rain showers. Thinking the bulk of this activity will track north
of the area today as there is better upper jet support across
northern Wisconsin. High pressure then builds into the Upper
Mississippi River Valley as a shortwave tracks across Nebraska and
southern Iowa. Any precipitation with this feature should remain
south of the area. With the drier air moving in today, look for
afternoon relative humidity values to fall into the 25 to 35
percent range across central into northern Wisconsin.

.LONG TERM...(Tuesday through Sunday)
Issued at 254 AM CDT Mon Mar 20 2017

Dry, cool Canadian high pressure will dominate the weather pattern
across the area Tuesday into Wednesday. Will have to keep a close
eye on low temperatures during this timeframe with the dry cool
airmass in place. Low lying areas that typically decouple may see
colder lows than what is currently forecast. On Tuesday plan on
afternoon relative humidity values once again falling into the 25
to 35 percent range across portions of western into central
Wisconsin. Wednesday looks to be the driest day as the high
settles overhead. Plan on afternoon relative humidity values
falling into the 20s and possibly teens for areas along and east
of the Mississippi River. Central Wisconsin will see the lowest
relative humidity values.

Forecast models are in good agreement bringing precipitation back
into the region late Thursday into Saturday as low pressure
tracks across the central plains and a trough works its way
through the Upper Mississippi River Valley. Warm air advection
working through the region Wednesday night may bring some light
snow to the area but the bulk of the precipitation will arrive
later on Thursday. Latest indications are that much of the
precipitation should fall in the form of rain as warm air is
pumped into the region with 850 mb temperatures warming to +3 to
+9 C. We could see a wintry mix on the leading edge of this warmer
air on Thursday but it would most likely be short-lived. The main
concern will then be rain across the area late Thursday through
Saturday. The GFS, ECMWF, and Canadian, are indicating total
rainfall amounts of 1 to 2 inches across the area with a better
signal for the higher rainfall amounts north of Interstate 90. If
these rainfall amounts are realized we could see some rises on
area rivers and streams. Since the soil moisture is rather high
across the area much of the rainfall would be runoff. Cannot rule
out a few rivers edging toward minor flood stage, but this will
all depend on how much and where the rain falls.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1220 PM CDT Mon Mar 20 2017

VFR conditions expected through the period as dry Canadian surface
high pressure gradually builds southward from Canada. Northerly
winds of 5-15 kts will diminish tonight before increasing to 10-15
kts by late morning Tuesday. Only some mid/high cloud cover is
expected at times through the period.

&&

.FIRE WEATHER...Today through Wednesday
Issued at 254 AM CDT Mon Mar 20 2017

Dry Canadian high pressure builds into the region late today into
tonight and remains over the region through Wednesday. Red Flag
weather conditions are not expected due to lighter winds.

This afternoon look for relative humidity values to drop into the 25
to 35 percent range across portions of central into northern
Wisconsin. Plan on north winds of 10 to 14 mph today.

Tuesday will be another dry day across the area with afternoon
relative humidity values falling into the 25 to 35 percent range
along and east of the Mississippi River. Winds on Tuesday will be
out of the north/northwest at 10 to 15 mph.

Wednesday is expected to be the driest day when afternoon
relative humidity values look to drop into the 20 to 25 percent
range along and east of the Mississippi River. Central and
northern Wisconsin could see values fall into the teens. The good
news is that winds will be light out of the east/southeast at 5
to 10 mph. Precipitation chances return late Wednesday night into
Thursday and higher humidity values will move back into the
region.

&&

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

$$

SHORT TERM.....Wetenkamp
LONG TERM......Wetenkamp
AVIATION...JM
FIRE WEATHER...Wetenkamp



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