Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 120916

Area Forecast Discussion
National Weather Service La Crosse WI
316 AM CST Sun Nov 12 2017

.SHORT TERM...(Today and tonight)
Issued at 316 AM CST Sun Nov 12 2017

09Z water vapor loop shows a well defined short-wave across
central SD. At the surface, an inverted trough extends from MO
into IA. Regional radars show widespread rains across much of IA
into IL with the northern extent of this precipitation impacting
the southernmost counties of the forecast area. Temperatures and
dewpoints have generally been steady between 32 and 34 degrees,
meaning rain should continue to be dominant p-type. That said,
could still see a few slick spots on cold untreated surfaces. This
rain will continue to move south and east early this morning,
exiting the forecast area by around 15Z.

Clearing skies north of I-90 may allow for areas of fog to
develop through sunrise, some of which could become locally
dense. Rochester and Austin, MN have flirted with 1/4 mile in fog
at times this morning, but increasing high clouds should help
limit additional fog development and reductions in visibility
across southeast MN.

For the rest of today, high pressure will build across the region.
Clouds across the south will slowly push east, although another
area of clouds currently across eastern ND and northern MN will
drop south across portions of the forecast area. While there could
be breaks of sun between these two cloud masses through the day,
partly sunny to mostly cloudy skies will be the rule. Afternoon
highs will top out in the mid 30s to lower 40s with light
northwest wind. Dry conditions will continue into tonight with
temperatures dependent on cloud cover. In general, most areas will
drop into the lower to mid 20s.

.LONG TERM...(Monday through Saturday)
Issued at 316 AM CST Sun Nov 12 2017

Surface high pressure drifts eastward on Monday, with southerly
return flow developing across the region. Skies will be partly
sunny with highs rising into the lower to mid 40s.

Low-level moisture advection and isentropic lift increase Tuesday
ahead of the next wave aloft. This could result in periods of
light rain or drizzle through the day, but with model soundings
showing no ice aloft, morning surface temperatures will need to
be watched closely for possible freezing impacts. Temperatures
warm enough into the afternoon for the p-type to be all rain.
Precipitation chances then increase further Tuesday night as a
surface cold front sweeps across the forecast area. Thermal
profiles continue to support rain, but deep layer moisture is
still lacking, so overall rainfall amounts will likely be on the
low-side, generally a tenth of an inch or less. Afternoon highs
Tuesday will top out in the 40s for most locations.

Dry conditions return Wednesday into Thursday with a progressive
surface high moving across the Upper Midwest. Temperatures in the
40s on Wednesday will drop a bit into Thursday with highs from the
mid 30s to lower 40s.

Still watching a strong Eastern Pacific trough for late in the
week. Model timing, strength, and placement differences persist
resulting in various surface low tracks and thermal profiles. Will
continue to follow a model consensus, keeping POPs generally in
the 30 to 70 percent range Thursday night through Friday. No
matter the model, the system looks to be east of the area by
Saturday, with a return to drier, but colder conditions.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1135 PM CST Sat Nov 11 2017

Cigs: tricky forecast. Northern edge of the current cloud deck sits
nearly on top of KRST/KLSE per latest fog/stratus satellite imagery.
Sfc obs point to sites mostly sub 3 kft. Meso models suggest the
edge will slip slowly south overnight, resulting in sct-bkn vfr
conditions. Given the southeast tack of the responsible shortwave
trough, that still seems reasonable - although it might take until
12z for KLSE.

Next concern is the mass of low clouds across eastern ND/northern
MN. Fog/Stratus satellite imagery shows it making very slow progress
south-southeast, not nearing the TAF sites (if it holds together and
keeps current direction) until early Sun afternoon. NAM/RAP low
level RH still favoring bringing this mass across the TAF sites -
especially KLSE - pulling east late in the evening. The GFS keeps it
just north/east, with minimal impact (especially KRST). Conundrum.
Low level ridge building in from the west could serve to shunt the
cloud mass far enough east by the afternoon to avoid any impact at
KRST...maybe even KLSE. Confidence not high in how this will play
out. If you like one set of models, there will be several hours of
MVFR for the afternoon. If you like another, its VFR through much of
the day.

For now, going to play some cig impacts at KLSE for the afternoon.
Will continue to monitor at update as needed.

Clouds will clear (if around) Sunday evening as high pressure builds

WX/vsby: see some threat for mvfr br at KRST with weaker gradient
building in, although some high clouds to contend with. Will add a
tempo group in with vsby restrictions showing just to their west at
late evening.

Winds: light south/vrb winds tonight should become more
northwesterly Sunday, still staying relatively light.




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