Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 192338

Area Forecast Discussion
National Weather Service La Crosse WI
638 PM CDT Sat May 19 2018

.SHORT TERM...(This evening through Sunday)
Issued at 339 PM CDT Sat May 19 2018

At 3 PM, a weakening low pressure system was located near Slater,
Iowa. Some sunshine ahead of this system has allowed mixed layer
CAPES to climb into the 500 to 1000 J/kg across eastern Iowa,
northwest Illinois, and southwest Wisconsin. This has allowed
showers and scattered thunderstorms to develop across central
Iowa. The meso models are in general agreement that the 0-6 km
effective shear will remain weak, so not anticipating any severe
weather. However, cannot rule out some gusty winds across parts
of northeast Iowa and southwest Wisconsin between 5 PM and 8 PM.

For late tonight and Sunday morning, another weakening trough will
produce showers and isolated storms as it moves northeast Iowa
and southwest and central Wisconsin. With weak shear and limited
CAPES, not anticipating any severe storms.

On Sunday afternoon, the meso models are trending drier across
the area. As a result, the rain chances were lowered some. If this
trend continues, the rain chances may be removed.

.LONG TERM...(Sunday night through Saturday)
Issued at 339 PM CDT Sat May 19 2018

From Sunday night through Monday night, the models continue to
show that a short wave trough will eject out of the Central
Plains and this system then move northeast through the Upper
Mississippi River Valley. With little instability, just went with
scattered showers. The combination of clouds and rain will result
in high temperatures in the lower and mid 60s on Monday.

From Tuesday night through Thursday, the 500 mb ridge will build
north into the region. While there is agreement with this, the
models continue to struggle with the placement of the warm front
during this time frame and this greatly impacts the amount of
instability across the region on Wednesday and Thursday. The GFS
has 2-3K CAPES on Wednesday and Thursday. Meanwhile, the ECMWF
holds these higher CAPES until Thursday. While the CAPES will be
increasing, the shear remains weak, so other than the possibility
on an isolated pulse severe storm no organized severe weather is


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 638 PM CDT Sat May 19 2018

MVFR ceilings continue at RST but should gradually rise to VFR
into late evening as drier air continues to work down across the
area, while LSE should see a thicker VFR cloud deck (around 4kft,
give or take) arrive the next few hours, holding firm for all
areas overnight. Can`t rule out a few showers developing northward
toward the I-90 corridor later tonight through Sunday morning, but
confidence not nearly high enough to include more than a
`vicinity` mention at this time. We should see some clearing work
from north to south for the afternoon at both LSE and RST, with
the loss of a ceiling expected at both sites by midday, though
that timing could slip a little based on real-time cloud trends
tomorrow. Winds gradually shift to a north/northeast direction
this evening and then a more easterly one for Sunday, mainly in
the 10-15 knot range, though some gusts to 20 knots are possible
at RST.




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