Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 142040
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
240 PM CST Tue Feb 14 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 240 PM CST Tue Feb 14 2017

An upper low was evident via water vapor imagery dropping
southeastward towards Lake Superior early this afternoon. A
secondary cold front has been sliding south across the region, but
the stronger 925 mb cold advection has been farther north through
early afternoon. As a result, it`s been another mild day with
highs reaching the 40s in quite a few areas.

A few isolated rain or snow showers will remain possible into the
early evening within steeper low level lapse rates as the upper
wave swings through, mainly along and east of I-94, but the window
for showers will be short as large scale subsidence increases
behind the upper wave. A very transitory cooler air mass behind
the cold front will drop across the region this evening and
tonight with temps falling back closer to seasonal averages. Lows
tonight will be in the teens to low 20s with highs in the 20s to
mid 30s on Wednesday.

Winds will remain on the gusty side into the evening with the
cold advection, steep low-level lapse rates and a relatively
tight pressure gradient. Winds will subside heading into Wednesday
as surface ridging passes over the area.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 240 PM CST Tue Feb 14 2017

An extended period of tranquil and increasingly spring-like weather
still is on tap late this week through the weekend. Mid/upper level
ridging will spread into the Northern Plains and Upper Midwest and
remain largely in place through the weekend. Steady low-level warm
advection will kick in and persist through Friday as 850 mb temps
climb from -2C to -8C Wednesday evening to around 11C to 13C by
Friday evening. These 850 mb temps would represent standard
anomalies of +2 to +3. Corresponding surface temps should rise
from the 30s and 40s on Thursday into the 50s for many areas on
Friday.

An upper level shortwave trough will pass across southern Canada
Friday night bringing a weak surface boundary into the region.
However, this should have minimal impact in terms of sensible
weather, with no precip and no drop off in temps as broad upper
ridging persists. Highs should remain in the 50s through the
weekend across much of the area, with 60 possibly in reach with
little snow cover in many areas.

A progressive upper trough ejecting out of the Rockies early next
week and associated frontal system will lead to increasing rain
chances later Mon/Mon night. A rumble or two of thunder is even
possible given some modest instability. Increasing low-level
return flow will help transport plentiful moisture ahead of the
system with temps continuing to be more typical of early to mid
April ahead of this system. As moisture/thermal advection
increases ahead of the approaching frontal system Sunday night
into Monday, temps may begin the day on Monday near or above 40 in
many areas. This will set the stage for another very warm day on
Monday, but timing of clouds and precip may impact high temps.
Temps will cool on Tuesday behind the front, but remain well above
average.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday noon)
Issued at 1141 AM CST Tue Feb 14 2017

A low will drop SE across Ont today then into the eastern great
lakes tonight. Winds are going to gradually swing from W to NW and
NNW this afternoon and tonight. Deeper diurnal warming/mixing this
afternoon is expected to produce winds of 12-20kt G22-30kt at the
TAF sites (stronger at higher elevation sites like KRST), with these
winds quickly diminishing to around 15kts with sunset. N-NW winds of
10-15kts then expected later tonight/Wed morning.

Bigger concern is lower clouds/moisture expected to wrap south
across the area tonight. Consensus of models spread in the lower
moisture and cloud decks in the 2500-3500 ft range late tonight and
for Wed morning. Again today at mid-day per obs and vis imagery,
models look too robust with the moisture/clouds upstream of the area
in Man/northern MN. Given lower confidence in lower cloud decks
later tonight/Wed morning, for now carried sct030-050 clouds tonight
with some bkn035 decks after 10-13z and thru much of Wed morning.

&&

.HYDROLOGY...
Issued at 306 AM CST Tue Feb 14 2017

Warmup looks on track for Thursday into the weekend. Daytime highs
are expected to warm from the 30s/40s on Thursday into the 40s/50s
for Friday into the weekend. These temperatures are expected to melt
much of the existing snow pack across the area. This snowmelt
combined with a frozen layer of ground is expected to cause runoff
into area streams and rivers. Right now, no flooding is expected but
within bank rises are likely along with the potential for a few ice
jams. Those with interests along streams and rivers will want to
keep up with the latest forecasts.

&&

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

$$

SHORT TERM...JM
LONG TERM...JM
AVIATION.....RRS
HYDROLOGY....DAS



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