Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 251651

Area Forecast Discussion
National Weather Service La Crosse WI
1151 AM CDT Sun Sep 25 2016

Issued at 715 AM CDT Sun Sep 25 2016

Flash flood watch has been cancelled. Radar/surface observations showing
generally less than 1/10 inch amounts in shower activity moving
into/across the area. Although scattered showers and isolated
thunderstorms are still expected today, this latest radar trend
and CAM trends into today show the potential for heavier rainfall
and threat of flash flooding has diminished significantly.


.SHORT TERM...(Today and tonight)
Issued at 354 AM CDT Sun Sep 25 2016

Main forecast concerns today are on brief heavy rain potential
through early afternoon. Focus then turns to windy conditions
developing tonight into Monday.

Showers and isolated thunderstorms have been working east across
southeast Minnesota and northeast Iowa early this morning. This
activity will continue to spread east into western and central
Wisconsin during the morning hours. Rainfall amounts have been on
the lighter side generally around 1/4 inch or less. Some pockets of
brief heavier rain noted over central Iowa early this morning but
this activity has really waned with the loss of CAPE due to
nocturnal cooling. Precipitable water values remain high at 1.4 to
1.9 but with very little CAPE to work with, these higher values
most likely won`t result in heavy rain. The precipitation this
morning across the local area has mainly been on the leading edge
of 850 mb moisture transport working through the region. The
moisture transport then pushes east after 12Z. Showers and storms
should then meander east across the area through the rest of the
morning hours ahead of a cold front. The front then looks to push
into western Wisconsin by early this afternoon. The 06Z NAM has
slowed the front progression and if this solution verifies we will
have to keep an eye on the potential for thunderstorm development
along the front. The latest CAMS suggest the thunderstorms develop
just east of the forecast area along the front. With shear
starting to catch up to the front, a few of the storms could be
strong to severe with the potential for large hail and damaging
winds. At this point it appears the main threat for heavy rain
would be confined to portions of northeast Iowa into far
southwest Wisconsin. Given the cold front has to pass through the
area yet, we cannot rule out some brief heavy rain along it.
Confidence is not high that we will see rainfall rates or amounts
high enough to produce flash flooding concerns but given how
vulnerable we are with the saturated grounds and ongoing river
flooding, will continue the flash flood watch. The main missing
ingredient is instability or CAPE to utilize the high precipitable
water values.

The cold front then pushes east of the area tonight as a vigorous
trough dives into the region. A tightening pressure gradient and
steepening lapse rates will lead to strong northwest winds of 10
to 20 mph with gusts of 30 to 35 mph possible. Winds will be
even stronger on Monday in open areas.

.LONG TERM...(Monday through Saturday)
Issued at 354 AM CDT Sun Sep 25 2016

Main forecast concerns in the long term are on windy conditions on
Monday along with chances for rain showers through Tuesday.

Strong northwest winds are expected across the area on Monday and
this may lead to some uprooting of weakened trees due to the very
wet soil conditions. Also, Winds speeds of 15 to 25 mph with
gusts to 40 mph are possible. We may even see some gusts to 45 mph in
the open areas of southeast Minnesota and northeast Iowa. Rain
showers are likely on Monday, especially along and north of the
interstate 94 corridor. It will be much cooler Monday into Monday
night with the upper low settling in. Plan on highs on Monday in the
upper 50s to around 60 with lows Monday night falling into the 40s.
Breezy conditions continue into Tuesday along with some rain showers
across central into northern Wisconsin as the upper low meanders
south over Lake Michigan. The low looks to finally exit the region
by late Wednesday with high pressure building in from the west. High
pressure will then dominate the weather pattern from Thursday into
Saturday with dry and quiet weather expected. Plan on highs mainly
in the upper 60s to around 70 with lows in the in the upper 40s to
lower 50s.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1151 AM CDT Sun Sep 25 2016

Late this morning the cold front was thru the KRST area with west
winds and rising/improving cigs. Front was approaching KLSE and will
move thru around 18z. Cigs at KLSE to then improve to VFR between 19-
21z as deep westerly/drying flow spreads across the area. Would then
expect good VFR at both sites thru the rest of the TAF period,
however, area of MVFR/VFR wrap-around strato-cu spreading southeast
across MN on the back side of the sfc-700mb trough axis. these
clouds to spread into KRST around 19z then southeast across the rest
of the area thru the afternoon. Drying/mixing slowly raising the
cigs hgts in this cloud area but did linger some bkn025 clouds at
both KRST/KLSE thru 22-23z. Improvement then thru the late
afternoon/early evening as deeper drying/subsidence from the Dakotas
spreads into the region. Good VFR expected from mid evening thru Mon
as deeper layered/dry NW flow spreads across the region.

NW gradient winds 15-25KT G25-35KT at the TAF sites by later Mon
morning and for Mon afternoon. This with a tighter pressure gradient
over the region and deeper diurnal warming/mixing to around 850mb,
where winds in the top half of the mixed layer will be 30-35kts.


Issued at 354 AM CDT Sun Sep 25 2016

Flash flooding is looking less likely across the area the rest of
this morning as showers and isolated thunderstorms work through the
region. There remains the possibility of rainfall amounts of 1/4
to locally 3/4 of an inch along a cold front moving through the
are this morning into early this afternoon. Given the saturated
soils and ongoing flooding cannot rule out some localized flash
flooding if any thunderstorms would repeat over the same
locations. River flooding continues for many locations today
however most rivers have crested and will continue to fall into
the work week.




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