Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 271740

Area Forecast Discussion
National Weather Service La Crosse WI
1240 PM CDT Thu Oct 27 2016

Issued at 1102 AM CDT Thu Oct 27 2016

Classic late October stratus day out there once again with
plentiful moisture stuck beneath a gradually building inversion
through the afternoon. We do see some breaks in the lowest clouds
working toward the I-35 corridor, though plenty of mid clouds and
even a few light showers streaming overhead will be enough to
maintain mainly cloudy conditions through the rest of the day.
Given that setup and based on the time of year, have lowered going
highs by about 5 degrees in many areas, though western spots could
see a small window to "warm up" by very late in the afternoon.

Pending cloud trends through tonight, fog does appear to be a
potentially more significant issue than earlier discussed. As the
925-850mb ridge axis crests the area through the evening, we will
increasing warm into the existing stratus deck, likely helping to
erode the lowest clouds from southwest to northeast all while we
moisten the still-rather-cool boundary layer in advance of low
pressure working into the northern Plains. Given what occurred to
our south overnight with widespread dense fog, do have some
concern that at least areas along/west of the Mississippi stand a
risk for dense fog development, mainly after the 03-06Z time frame
tonight. Will need to evaluate late afternoon cloud trends to get
a better feel, but have already increased wording for fog in the
forecast, with an advisory not out of the question at some point
later tonight.


.SHORT TERM...(Today through Tonight)
Issued at 343 AM CDT Thu Oct 27 2016

Current GOES IR imagery showing the region engulfed in widespread
stratus in the wake of low pressure over northern Indiana. GOES
cloud thickness product indicating this stratus varying from 800-
1200ft thick, so not expecting any clearing overnight as a ridge of
high pressure builds overhead by daybreak. In fact, this stratus
looks to be be pretty stubborn today with perhaps some breaks west
of the Mississippi. With anticipated cloud cover, temperatures will
suffer some with highs ranging from the middle and upper 40s along
and northeast of I-94 to the lower/middle 50s elsewhere.

Southerly winds pick up through the night tonight as low pressure
moves into the Dakotas. NAM bufkit along with majority of hi-res
models showing the potential for more stratus/fog across the area
tonight as fetch of moisture moves north out of the Southern
Plans/Gulf in this southerly flow. Have partly to mostly cloudy
going across the area, along with patchy fog mention west of the
Mississippi River. Hopefully fog doesnt get too out of hand given
the very moist ground/lower boundary layer...something to keep an
eye on. Overnight lows look to be near 40 across central the
middle 40s west of the Mississippi River.

.LONG TERM...(Friday through Wednesday)
Issued at 343 AM CDT Thu Oct 27 2016

Friday could potentially be a bit tricky given potential for stratus
in moist southerly flow. Better potential for boundary layer
mixing/sunshine will be across northeast IA/far southwest WI. Rest
of the area looks to be in the stratus. This will have a definite
impact on temperatures. Right now...going for lower 60s across
central WI to the the upper 60s across northeast IA/far southwest
WI but this may be a bit optimistic if more stratus materializes.
Also of note will be gusty south winds in the 15-25 mph range with
gust around 35 mph across the bluff tops along the Mississippi River
and the more open areas of northeast IA/southeast MN.

A cold front oozes slowly southward across the area Friday night
into Saturday setting up a zone of baroclinicity. Meanwhile...the
NAM/GFS/ECMWF all show a weak mid-level trough working on this
baroclinic zone Saturday into Saturday night for a chance of
showers. Otherwise, looks mostly cloudy through Saturday night with
highs Saturday ranging from the lower/middle 50s across northern WI
to the lower/middle 60s across northeast IA/far southwest WI.

High pressure moves in Sunday for a pleasant autumn day. Look for
highs right around normal in the 50s.

Rain chances return Monday/Monday night as a rather strong low
pressure system moves east out of the Dakotas and across Lake
Superior. This system has the potential to pull some unseasonably
warm air northward into the region Monday. Right now...looking at
highs Monday ranging from the upper 50s across northern WI to the
middle/upper 60s across the rest of the area.

After what looks to be a quiet Tuesday under high pressure, look for
rain chances again Wednesday as a weak Mid-level trough ripples
northeast out of the Central Plains toward the region.
Otherwise...temperatures look to be a few degrees above normal with
highs well into the 50s.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1240 PM CDT Thu Oct 27 2016

Widespread stratus continues to encompass much of the region, but
should slowly erode from the south and west into the evening and
early overnight hours as southerly flow increases. Current
ceilings in the IFR to MVFR range will very slowly rise through
early evening, with the expectation that lower stratus will
completely exit LSE and RST by 05Z, though ultimately that timing
could end up being a little slower. With moistening though the
boundary layer taking place overnight in advance of low pressure
over the northern Plains, the fog threat continues to increase,
especially for RST where skies will be clearest for longer.

Have really kicked the fog idea into high gear with a period of
LIFR conditions roughly 10-14Z, though the exact timing of that is
still a bit in question. Farther east for LSE, not entire sure
just how low visibility will go given the later clearing skies,
but there is some smaller risk for LIFR conditions for a time
centered on sunrise. Any fog (and maybe a little additional
stratus) should erode by mid morning, leaving gusty southerly
winds at 15-25 knots heading into midday Friday.


Issued at 343 AM CDT Thu Oct 27 2016

Minor flooding continues along the Cedar River in southeast
MN/northeast IA, as well as along the Turtle Creek near Austin MN.
Minor flooding is also forecasted for the Trempealeau River in west-
central WI. See the latest Flood Statements for the specific river
forecasts. Other rivers...streams and creeks also have rises but
will remain below flood stage.




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