Area Forecast Discussion
Issued by NWS La Crosse, WI

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738
FXUS63 KARX 150532
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1132 PM CST Tue Nov 14 2017

.UPDATE...
Issued at 1058 PM CST Tue Nov 14 2017

The visibility has improved into the 1 to 3 mile range across all
of northeast Iowa and southeast Minnesota. Not expecting the dense
fog to return as the south flow has increased ahead of the
approaching cold front and as a result, the dense fog advisory was
canceled.

&&

.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 adjust 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 06Z TAFS through 06Z Wednesday night)
Issued at 1132 PM CST Tue Nov 14 2017

Widespread IFR conditions continue across the area ahead of the
approaching cold front. The front will move across the region late
tonight into early Wednesday morning switching the winds around to
the west/northwest which will clean out the surface moisture and
allow the visibility to improve to 7 miles or better. However, not
expecting the ceilings to improve that fast as forecast soundings
continue to show the low level moisture will get trapped below the
inversion which could keep MVFR ceilings in place well through the
day. Will continue to optimistically show a period of VFR for the
late morning and early afternoon at KRST before the clouds move
back south in the cyclonic flow around the surface low and bring
the MVFR back in. For KLSE, even less confident that VFR
conditions will occur and have essentially stayed with MVFR
through the day.

&&

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

$$

UPDATE...04
SHORT TERM...Shea
LONG TERM...Shea
AVIATION...04



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