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Area forecast discussion 
National Weather Service La Crosse WI
510 PM CST Thursday Mar 5 2015

Short term...(tonight through Friday night)
issued at 213 PM CST Thursday Mar 5 2015

Ridge of high pressure dead overhead this afternoon with clear skies
and very chilly temperatures in the upper single digits and lower
teens above zero.

For tonight...the ridge of high pressure will shift east of the area
as a warm front approaches from the northern plains. This sets up
warm air advection overnight on increasing southerly winds. Plan on
temperatures to dip into the single digits below/above zero this
evening...then starting a slow rising trend overnight.

Warm front makes passage through the area on Friday with 925mb
temperatures increasing some 10c from Thursday into the -8 to -2c
range. There will be some increase in middle-level cloud...but not
enough to keep the sun from having its affect in combination with
the warm air advection. As a result...look for temperatures to
moderate into the upper 20s to the middle 30s.

For Friday night...northwest flow aloft brings a wave of low
pressure across southern Canada/Lake Superior. Appears better
precipitation chances associated with the forcing of this wave will
stay north of the area...but maintained a small chance north of I-
94. Otherwise...low temperatures look to be in the upper teens to
lower 20s.

Long term...(saturday through thursday)
issued at 213 PM CST Thursday Mar 5 2015

Focus in the long term will be possible accumulating snow Saturday
night into Sunday morning...then quiet with a warming trend into
next week.

Will have to contend with a lingering small snow chance across the
north...north of Highway 29 Saturday morning as a middle-level trough
swings across that area. Otherwise...looking like a partly sunny day
with highs in the middle 30s to near 40.

Latest 05.12z European model (ecmwf)/Gem in good agreement in bringing a fairly
vigorous middle-level trough/weak surface low across southern
Minnesota/southern WI Saturday night into Sunday morning. Moderately strong
dynamics for forcing despite low-end available moisture. The ec
shows right entrance region of 105-110kt 300mb jet and moderate 850-
700mb frontogenesis. As such...thinking there will be a fairly
tight/focused area of snow south of the I-94 corridor in Wisconsin.
Right now..looks like 1-2 inches of snowfall will be possible late
Saturday night into Sunday morning...before the wave departs to the
southeast by afternoon. Will have to keep an eye on this forcing as
it could squeeze out a bit more moisture and therefore more
snowfall. For now...bumped probability of precipitation into higher chance category since
GFS/NAM are fairly dry yet. Looks like this snow will be melting
going into Sunday afternoon as highs warm back into the middle
30s/around 40.

For Monday through Thursday...latest 05.12z GFS/European model (ecmwf) continue to
show building height/upper level ridging taking place over the
central Continental U.S.. this will lead to warming temperatures with highs
Monday looking to be in the upper 30s to the middle 40s...and into
the middle 40s/middle 50s by Wednesday. Going highs on Thursday
right now cool back into the upper 30s to the middle 40s...but feel
they may have to be bumped up as well with models coming into better
agreement on ridge amplification.

&&

Aviation...(for the 00z tafs through 00z Friday evening)
issued at 510 PM CST Thursday Mar 5 2015

A surface high will continue to slip southeast tonight...with a
tightening pressure gradient replacing it. Winds will be on the
increase through the night as a result...and should stay breezy
through Friday morning. The strongest winds will likely occur in the 08-
14z time frame. Low level wind shear is a concern as rap/nam12 BUFKIT soundings
suggesting 40+ kts of wind by 2 kft roughly from 08-13z. Bigger
concern for klse which will have a bit less surface wind compared to
krst.

The NAM points to increasing near surface moisture on Friday...which
would result in at least an MVFR deck of clouds. Its likely the
result of anticipated snow melt. The GFS is drier. No evidence of
this on satellite or via surface observation...and not much for snow pack in the
source region of the wind /at least until you get into northern IA/.
Will stick with VFR clouds - if any - for now.

&&

Arx watches/warnings/advisories...
WI...none.
Minnesota...none.
Iowa...none.
&&

$$

Short term...das
long term...das
aviation...rieck

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