Area Forecast Discussion
Issued by NWS La Crosse, WI

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277
FXUS63 KARX 271947
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
247 PM CDT Thu Apr 27 2017

.SHORT TERM...(Tonight through Friday night)
Issued at 247 PM CDT Thu Apr 27 2017

GOES Water Vapor imagery this afternoon showing the mid-level wave
responsible for snowburst east of the Mississippi River this morning
now exiting into northeast WI. Radar still showing some lingering
rain/snow shower activity across the area in steep low level lapse
rate/cold cyclonic flow. Temperatures this afternoon were chilly
with readings in the 30s. West winds 10-20 mph were adding a bite to
the chilly air.

For tonight, a ridge of high pressure builds in from southwest to
northeast for clearing skies allowing for good radiational cooling
given light airflow. Depending on how much decoupling takes place,
will likely see some freezing temperatures across the area. And,
given the advanced blooming of vegetation across some of the area,
concerned for some plant/bloom damage. As such, have frost headlines
posted for areas along the Mississippi/Wisconsin Rivers where
progression of Spring/blooming has advanced.

Models continue to show a mid-level wave/weak surface low rippling
northeast across IA/IL Friday afternoon into Friday night. Fairly
strong frontogenesis noted by the NAM/GFS centered around 700mb
sliding through the region. This should be sufficient for isolated
to scattered showers south of I-94, more numerous south of I-90.
Otherwise, looks a bit warmer for highs with readings in the upper
40s/lower 50s. Friday night may need frost headlines again for
portions of the area as temperatures dip into upper 20s to the
middle 30s.

.LONG TERM...(Saturday through Thursday)
Issued at 247 PM CDT Thu Apr 27 2017

Looks like a dry start to Saturday but then rain chances spread south
to north into the area through the day ahead of cyclogenesis over
the southern Plains. Otherwise, plan on increasing clouds with highs
in the upper 40s to the middle 50s.

Strengthening low pressure moves out of the Southern Plains toward
the region Saturday night through Monday for an increasingly wet
period. GFS and NAM still showing precipitable water values in the 1-
1.25 inch with a wide-open gulf tap. Right now, looking at rainfall
from Saturday night through Sunday in the 1/3 to 1 inch range with
potentially another 1/2 to 1 inch through Monday. See hydrology
section below for impact on area rivers. Otherwise, looks like a
cold rain with highs Sunday and Monday mainly in the 40s. Look for
mixing of the rain with snow later Monday night as column cools with
low becoming vertically stacked.

Cool cyclonic flow aloft continues through Tuesday for a chance of
showers as highs top off in the upper 40s to the upper 50s.

Temperatures slowly rebound Wednesday and Thursday with that closed
low filling/moving off to the east. Still a couple weak waves
rippling through we`ll have to keep an eye on for slight shower
chances. Right now, they don`t look too impactful.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1235 PM CDT Thu Apr 27 2017

MVFR cigs mostly 1500-2500 ft to gradually lift into the 2500-3500
ft range thru the afternoon. Then question becomes when will the
cloud decks dissipate/clear out. Latest set of model soundings and
lower level RH progs showing the clouds to linger thru the evening,
then decrease around and shortly after midnight as stronger
subsidence and a lower level ridge of high pressure builds east into
the region. Generally good VFR then expected thru the over night
hours and Fri morning with the drier sfc-700mb ridge axis over the
area. West-NW winds this afternoon will decrease late this
afternoon/early this evening, then generally be SW to NW 5-8kt or
less during the late evening thru morning hours of Fri.

&&

.HYDROLOGY...(Concerning rainfall this weekend)
Issued at 247 PM CDT Thu Apr 27 2017

Looking at another very wet weather system moving through the region
Saturday night through Monday. Right now looking at 1 to 2 inch of
rainfall through the period. Plan on river rises but not
anticipating any flooding at this time.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Frost Advisory from 1 AM to 8 AM CDT Friday for WIZ041-053>055-
     061.

MN...Frost Advisory from 1 AM to 8 AM CDT Friday for MNZ088-096.

IA...Frost Advisory from 1 AM to 8 AM CDT Friday for IAZ011-030.

&&

$$

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



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