Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 140817
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
317 AM CDT Sat Oct 14 2017

.SHORT TERM...(Today and tonight)
Issued at 317 AM CDT Sat Oct 14 2017

Main impactful weather concerns are on the potential for locally
heavy rainfall this afternoon and evening. Focus then turns to
strong west/northwest winds late tonight into early Sunday morning.

Dense fog will gradually improve this morning as cloud cover
increases from the south. Showers and thunderstorms become
numerous by this afternoon into this evening as low pressure
tracks through the region. There is the potential for locally
heavy rainfall across portions of northeast Iowa into far
southwest Wisconsin. Precipitable  water values climb into the
1.25 to 1.75 inch range producing standardized anomalies of +2 to
+4. Meanwhile, 850 mb moisture transport focuses into northeast
Iowa and far southern Wisconsin by mid afternoon then quickly
veers into northern Illinois and southeast Wisconsin as the low
moves in. Repeated rounds of thunderstorms could lead to localized
flooding this afternoon and evening. Confidence was not high
enough to issue a flash flood flood watch given the progressive
nature of the thunderstorms this afternoon. Will have to keep a
very close eye on this. Also, we may see other severe weather
threats mainly across far southern Wisconsin in addition to heavy
rain. This will all be heavily dependent on the position of the
surface warm front. At this time it appears the warm front will
stay just south of the local area but if it edges just a little
further north Grant County and Clayton County could see a severe
storm or two with damaging winds. An isolated tornado cannot be
ruled out closer the warm front but again this looks to stay south
of the area. Rain will taper off this evening into the overnight
as the low tracks northeast and away from the area. Thats when
strong west/northwest winds of 15 to 25 mph with gusts to around
40 mph develop. The strongest winds will be across the open areas
of southeast Minnesota and northeast Iowa as well as the ridge
tops of western Wisconsin. The winds will subside after sunrise.

.LONG TERM...(Sunday through Friday)
Issued at 317 AM CDT Sat Oct 14 2017

Main forecast concerns in the long term are on frost/freeze
potential Sunday night into Monday morning.

Windy conditions will gradually subside during the day on Sunday as
surface high pressure builds in from the west.  It will be a cool
day across the region with 850 mb temperatures ranging from 0 to
-1.5 C. This will result in high temperatures only in the upper
40s to lower 50s. This will set the stage for a rather chilly
temperatures Sunday night into Monday morning. Look for
temperatures to fall into the 30s with some mid 20s possible in
favored cold spots across central Wisconsin. Areas of frost are
expected, with more widespread frost likely along and east of the
Mississippi River. There will be a pressure gradient in place and
weak warm air advection so this may result in frost not being as
widespread across portions of southeast Minnesota and northeast
Iowa, mainly areas along ridge tops or open areas that typically
do not decouple.

Beyond Monday, it will be a rather quiet stretch of fall weather.
Broad weak ridging develops over the central CONUS.  The main
impactful weather to keep an eye on will be breezy southerly winds
at times.  With dry weather expected through the week we could see
an increased potential for a few crop/field fires with harvest
well underway. Afternoon relative humidity values don`t appear to
be particularly low, but forecast models may be overdoing
afternoon dew points after looking at the forecast soundings
during the afternoon hours. Main afternoons of concern are
Wednesday, Friday, and possibly Saturday depending on cloud trends
and potential precipitation moving in.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1146 PM CDT Fri Oct 13 2017

High pressure remains just north of the area, with earlier
clearing allowing for rapid fog development at LSE while RST
remains clear. Expect dense fog to remain in place for LSE through
about sunrise, though it may lift a little before then as winds
start to increase after 10Z/5 AM. RST should remain VFR with
mainly clear conditions the next few hours.

That all changes through late morning and this afternoon with low
stratus working back north ahead of approaching low pressure.
Expect a transition back to MVFR and eventually IFR for all areas
by late afternoon, along with periods of showers and drizzle. Some
thunder remains possible at LSE, but confidence not there to
include just yet.


&&

.HYDROLOGY...Today through This Evening
Issued at 317 AM CDT Sat Oct 14 2017

Localized flooding possible across portions of northeast Iowa into
far southwest Wisconsin this afternoon and evening. Strong
thunderstorms are possible this afternoon with the potential for
heavy rainfall of 1 to locally 3 inches. Clayton and Grant
counties have the highest chances of seeing heavier rainfall. Will
be issuing a Hydrologic Outlook to highlight this potential. At
this time it appears the main flood threat will be south and east
of the area across northern Illinois into southeast Wisconsin.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Dense Fog Advisory until 7 AM CDT this morning for WIZ029-
     032>034-041-042.

MN...Dense Fog Advisory until 7 AM CDT this morning for MNZ088-095-
     096.

IA...Dense Fog Advisory until 7 AM CDT this morning for IAZ009-010.

&&

$$

SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION...Lawrence
HYDROLOGY...Wetenkamp



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