Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KARX 200328

Area Forecast Discussion
National Weather Service La Crosse WI
1028 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 06Z TAFS through 06Z Sunday night)
Issued at 1028 PM CDT Sat May 19 2018

Weak upper level low pressure just to our south will slowly spin
northeast and weaken through the coming day, maintaining
widespread cloud cover mainly in VFR range but with some potential
for MVFR ceilings at times to work in from the east overnight.
Ahead of that feature, some showers are very much possible at LSE
and RST overnight and into Sunday morning, though confidence in
how widespread they will be remains low. Will maintain a
"vicinity" wording for now but will have to watch trends as some
briefly heavier showers can`t be ruled out. Will also have to
watch the northern extent of cloud cover by later tomorrow as
drier air erodes the northern edge of the cloud deck, with the
potential for LSE to scatter out while RST likely sits just on the
edge, though still with mainly just VFR ceilings. Winds will be
from the east to northeast, generally 10-15 knots but occasionally
higher at RST.




AVIATION...Lawrence is the U.S. government's official web portal to all federal, state and local government web resources and services.