Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 280720

Area Forecast Discussion
National Weather Service La Crosse WI
220 AM CDT Fri Jul 28 2017

.SHORT TERM...(Today and tonight)
Issued at 220 AM CDT Fri Jul 28 2017

Surface high pressure will be centered over Lake Superior today
and tonight, keeping the forecast area in light northeast near
surface flow. Based on latest upstream satellite observations and
model soundings, could see periodic cumulus through the day, but
mostly sunny skies will be the rule. 925 hPa temperatures by 00Z
tonight are around 1-2 degrees Celsius lower than yesterday, so
afternoon highs should be a few degrees cooler, topping out in the
upper 70s to lower 80s. Combined with dewpoints in the 50s, today
will be quite comfortable.

Mostly clear skies and light/variable wind tonight should lend
itself to possible fog development, especially in river valleys
and the cranberry bogs of west central WI. Lows will drop into the
lower to mid 50s.

.LONG TERM...(Saturday through Thursday)
Issued at 220 AM CDT Fri Jul 28 2017

With weak northwest flow aloft and persistent surface high
pressure, Saturday through Monday will be dry and pleasant. Could
see a little more cloud cover on Sunday with the passage of a weak
short-wave aloft. Otherwise, partly to mostly sunny conditions
will continue. Primary weather impact will be the potential for
morning valley/bog fog each day. GFS/NAM soundings are in good
agreement showing light winds (10 kts or less) up to 5-6 km each
morning. Skies also expected to be mostly clear. Potential limiting
factors will be degree of near surface saturation and the fact
that nights are still relatively short, but added patchy fog
through Monday morning. Daily highs will be in the upper 70s to
lower 80s with lows mainly in the 50s to near 60 degrees.

Tuesday and Wednesday, a stronger 500 hPa closed low will move
across the Hudson Bay area with a trailing cold front across the
Upper Midwest. This will result in a chance for showers and storms
mid-week. Not overly impressed with available forcing per 500 to
300 hPa potential vorticity advection progs, but PWATS do rise
to around 1.5 inches, so chance POPs seem reasonable at this
time. While instability does increase with dewpoints back into the
60s, weaker shear should preclude severe storms.

High pressure builds back across the region for Thursday with a
return to dry weather. Expect highs in the upper 70s/lower 80s
to end the work week.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1100 PM CDT Thu Jul 27 2017

Cigs: high pressure will keep skies skc/sct into Sat. The one caveat
is the potential for fog and/or stratus in the river valleys the
next couple nights. See some potential for a sub 1 kft cig at KLSE
if the scenario plays out. Not confident enough to add to forecast
at this time.

WX/Vsby: potential for river valley fog the next couple nights that
could impact KLSE. Light winds tonight favorable for the potential,
but the t/td spread of 15F at 03z is not. Deep light wind field
would also support river valley fog, but think the t/td spread will
be tough to overcome, and will keep any mention out the KLSE taf for
now. Similar setup for Sat morning, and might hold a better shot for
fog. Approaching the climatological favored time frame for valley
fog at KLSE.

Wind: north/northeast through Friday night. Mostly light, with a
little diurnal bump for Fri afternoon.




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.