NWS-La Crosse Forecast Discussion

 

						FXUS63 KARX 091744
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1144 AM CST Sun Dec 9 2018

.SHORT TERM...(Today and Tonight)
Issued at 251 AM CST Sun Dec 9 2018

Main forecast concerns in the short term are on cloud trends this
morning and the potential for patchy fog tonight.

Stratus is finally edging eastward across the forecast area this
morning and has cleared southeast Minnesota and northeast Iowa.
The stratus will be slow to exit central Wisconsin but should by
early afternoon as westerly winds in the 900 to 2kft layer persist
at 9 to 15 kts. Otherwise, the region remains under the influence
of surface high pressure as a mid level low moves southward
across eastern South Dakota into eastern Nebraska. Forecast
soundings suggest the potential for some patchy fog and perhaps
some low stratus in spots as weak low level warm air advection
moves into the region tonight. It appears locations over
northeast Iowa, southeast Minnesota, and north central Wisconsin,
could see some low cloud development, and possibly fog. Have
nudged sky cover slightly higher over these areas and included
patchy fog in the forecast. Mesoscale models also point toward
some fog over these areas, and with temperatures falling into the
teens again tonight, cannot rule out some freezing fog in spots.

.LONG TERM...(Monday through Saturday)
Issued at 251 AM CST Sun Dec 9 2018

Main forecast concerns in the long term are on precipitation chances
and temperatures.

Upper level ridging moves across the area Monday into Tuesday
providing quiet weather. The next system impacts the area Tuesday
night into Wednesday with the potential for rain and snow, and
possibly some freezing drizzle early in the day on Wednesday.
Forecast soundings late Tuesday night into Wednesday morning show
a lack of ice aloft which indicates the potential for freezing
drizzle as low level moisture increases. Saturation looks to
finally deepen enough for precipitation to switch over to snow
Wednesday morning and we could even see some rain mix in across
portions of northeast Iowa into far southern Wisconsin, if
temperaturers warm enough. Confidence on the low track and
precipitation arrival time is low during this timeframe so have
not included freezing drizzle in the forecast yet, but if trends
continue this will have to be added. Beyond Wednesday, a weak
trough moves through on Thursday, but doesn't look to produce much
if any precipitation over the region. The low we were watching
for Thursday into the weekend now looks to stay well south and
east of the region so it's likley this timeframe will be dry and
potentially a little warmer as ridging attempts to build in.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1143 AM CST Sun Dec 9 2018

Main concern will be the potential for stratus and fog
development tonight into Monday morning. Favorable conditions
would be a rather moist lower boundary layer. Less favorable will
be some mixing through the boundary layer to prevent widespread
development. Will have to keep a close eye on this balance going
into this evening. For now, have included 2-3sm br and sct006-008
in the KRST/KLSE TAFS after midnight. Will keep the scattered
stratus in after 15z but improve visibilities as boundary layer
mixes more with southwest winds 5-10kt.

&&

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

$$

SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION...DAS