Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 192340

Area Forecast Discussion
National Weather Service La Crosse WI
640 PM CDT THU MAY 19 2016

.SHORT TERM...(This evening through Friday)
Issued at 345 PM CDT Thu May 19 2016

AT 3 PM, a 1022 mb surface high was centered over Lower Michigan.
With mostly to partly sunny skies, temperatures have warmed into
the mid and upper 60s north of Interstate 94 and around 70 for the
remainder of the Upper Mississippi River Valley. The combination
of deep mixing (up to 750 mb) and the clockwise circulation around
the high pressure area caused surface dew points to be 5 to 10F
lower than the MOS guidance.

With dry air over the region, temperatures will quickly fall late
this evening and overnight. By sunrise on Friday morning,
temperatures in central and north-central Wisconsin will range
from mid-30s to lower 40s. These temperatures will be cool enough
for some patchy frost, but the coverage and certainty was too low
to issue a Frost Advisory. Meanwhile the remainder of the area
will see low temperatures in the 40s tonight.

On Friday afternoon, a short wave trough, currently over eastern
Kansas, will move east northeast through the Mid Mississippi River
Valley. Soundings continue to show that the moisture will be
limited to 50 to 100 mb. Both the NAM and GFS have surface based
CAPES climbing to around 250 J/Kg. However their dew points look
to be 5 to 10F too high. As a result, these CAPE values look too
high. Due to this, opted to keep the forecast dry.

.LONG TERM...(Friday night through Thursday)
Issued at 345 PM CDT Thu May 19 2016

On Friday night and Saturday morning, a northern stream short
wave trough will move southeast through the Upper Mississippi
River Valley. Like it`s predecessor on Friday afternoon the
moisture is rather limited (25 to 50 mb). As a result, kept the
forecast dry.

In the wake of this system, a ridge of high pressure will build
across the region for the weekend. This high will provide mostly
clear to partly cloudy skies. With the 925 mb and 850 mb
temperatures warming 2 to 4C through the weekend, high
temperatures will be in the mid and upper 70s on Saturday
afternoon and near 80 on Sunday afternoon. Like the past couple of
afternoons, soundings suggest that the dew points will be about 5
to 10F drier than the MOS guidance for Saturday. This will lower
the afternoon relative humidity values into the 25 to 35 percent

From Monday afternoon into Tuesday, a short wave trough will
flatten the upper level ridge across the region. Both the GFS and
GEM show that there will be a band of showers and storms located
along and ahead of this system. Meanwhile the ECMWF continues to
hint that there could be the potential for a split in the
precipitation as it moves move through the area. This is due to
one short wave trough moving to our southeast and yet another one
moving to our northwest. If this occurs, precipitation would be
more scattered and lighter than what the GEM and GFS indicate.
Due to this uncertainty, stayed with the model consensus. With
both the 0-3 km and 0-6 km shear less than 20 knots, not
anticipating any severe weather at this time.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 640 PM CDT Thu May 19 2016

VFR conditions will continue at KRST/KLSE through 21.00Z. Clear
skies this evening and overnight will give way to VFR cumulus on
Friday in the 6000 to 7000 ft agl layer. Could see some periods of
broken ceilings, but think highest mid-level moisture plume and
more widespread ceilings will remain farther west across central/
western MN and IA. Winds will be light from the southeast,
generally 10 kts or less.


.ARX Watches/Warnings/Advisories...


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