Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
FXUS63 KARX 142101

Area Forecast Discussion
National Weather Service La Crosse WI
300 PM CST Tue Nov 14 2017

.SHORT TERM...(Tonight and Wednesday)
Issued at 300 PM CST Tue Nov 14 2017

Messy forecast for this evening, but luckily temperatures are all
above freezing so any precipitation should remain liquid. Main
challenge for this evening will be dense fog potential, especially
west of Mississippi River.

Approaching mid level trough continues to hold area in warm air
advection regime, with hints of a warm front laid up across
northeast Iowa as of 19z. Along and ahead of this front visibilities
have been limited, especially across parts of northeast Iowa into
southern Minnesota as higher dew points trying to advect in.

While visibilities have fluctuated somewhat, and vary from area to
area, short term guidance, including latest HRRR surface visibility
fields, suggest parts of southeast Minnesota and northeast Iowa
could actually worsen before improving this evening. Some of this
depends on where precipitation increases at as wave approaches. If
bulk of that stays north and east of fog area, see no reason why fog
would magically improve. Will include an advisory for the evening
hours and perhaps later shifts can ajust as needed.

Meanwhile, short term guidance consistent with idea of light
precipitation this evening, but varies in exact area coverage.
Probably a mix of drizzle or rain, with better chance for just rain
further east.

As main wave slides through early Wednesday, precipitation chances
will end from west to east, even as colder air begins to filter in.
Secondary short wave dropping through western Great Lakes, could
also generate a little additional light precipitation /mix of rain
and snow/ along and north of Interstate 94.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 300 PM CST Tue Nov 14 2017

Quiet weather settles in for a bit mid week, with ridge passage
Wednesday night. If winds settle for a bit and skies clear at all,
could see low temperatures bottom out in bog areas of central
Wisconsin so lowered them a bit.

Otherwise attention turns to next wave late in the week, with
initial warm air advection possible already Thursday night. Not
expecting any significant impact with precipitation but warmer air
Friday should transition any threat over to mainly rain. Have
continued to trend rain threats higher as energy phases with trough
passage by Friday night.

Colder air returns on Saturday so exiting precipitation could
briefly switch over to light snow or flurries before ending, with
blustery, northwest winds setting the stage for a chilly weekend.

Lots of variability in medium range guidance for next week.
Models have been hinting at more of a blocking, high amplitude
pattern setting up which could mean extended cool and dry period.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday noon)
Issued at 1119 AM CST Tue Nov 14 2017

A very moist lower level airmass, trapped under an inversion near
900mb, will remain over the area this afternoon into Wed morning.
The present MVFR/IFR and lcl LIFR cigs with areas of MVFR/IFR vsbys
in BR are going to persist thru the afternoon. Deeper moisture and a
a round of lift will spread across the area tonight. Periods of -RA
are expected at the taf sites, mainly 00-08z at KRST and 02-10z at
KLSE. The -RA should help keep cigs/vsbys from dropping to VLIFR at
sites like KRST and LIFR at sites like KLSE during the later evening
and overnight hours. A cold front is set to push across the area
later tonight, moving thru KRST around 09z and KLSE around 12z.
Behind front will be a switch to brisk/gusty NW winds and an influx
of drier air.

Cigs/vsbys will improve behind the front and thru Wed morning, but
question remains how long will bkn/ovc MVFR cloud decks hold on.
Model soundings/x-sections showing plenty of lower level moisture to
remain trapped under the inversion well into Wed afternoon. For now
trended a bit optimistic with the lower cloud decks becoming sct
around 15 at both sites, but confidence not overly high with this.


MN...Dense Fog Advisory until Midnight CST Tonight for

IA...Dense Fog Advisory until Midnight CST Tonight for



AVIATION...RRS is the U.S. government's official web portal to all federal, state and local government web resources and services.