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Area forecast discussion 
National Weather Service La Crosse WI
1058 PM CDT Wednesday Jul 23 2014

Short term...(this evening through thursday)
issued at 316 PM CDT Wednesday Jul 23 2014

Main forecast concerns in the short term are on valley fog
potential and low temperatures tonight.

High pressure will build into the forecast area this evening and
tonight providing mostly clear skies and cool overnight
temperatures. The clear skies and cool temperatures will set the
stage for areas of fog along valley locations and across central
Wisconsin Cranberry country. After the fog Burns off Thursday
morning plan on mostly sunny skies across the area with high
pressure in control. With some lingering low level moisture will
likely see a few to possibly scattered cumulus clouds around. Look
for high temperatures to range from the middle 70s to around 80.
Winds will swing around to the south tomorrow afternoon into
tomorrow evening as the high slides east and low pressure
approaches from Dakotas.

Long term...(thursday night through wednesday)
issued at 316 PM CDT Wednesday Jul 23 2014

The low is expected to slide southeast Thursday night into Friday
morning. 850 mb moisture transport focuses into the areas along and
west of the Mississippi River Thursday night into Friday morning. A
thunderstorm complex looks to develop over eastern North Dakota
Thursday evening then is expected to push southeast into the upper
Mississippi River valley...with additional showers and storms firing
ahead of it late in the night on the nose of a strengthening low
level jet. There is fairly good model agreement that showers and
storms will impact southeast Minnesota...northeast Iowa...and
portions of southwest Wisconsin late Thursday night into Friday
morning. 0-3 km MUCAPE values look to range from 1200 to 2000 j/kg
late Thursday night into early Saturday morning with 0-3 km bulk
shear values of 30 to 45 kts. This could support the potential for
a few strong to perhaps severe thunderstorms. Also...precipitable
water values are fairly healthy ranging from 1.5 to 1.8. The
precipitable water values combined with warm cloud depths of 4 km
suggest the storms would be efficient rain producers and may cause
some concerns especially in urban areas. With the recent dry
weather over the region the soils would be able to take some rain
so any hydrology concerns would hinge on precipitation rate. Will
have to keep a very close eye on this system.

Chances for showers and storms linger Friday into Friday night but
then we should see a break in the activity on Saturday ahead of a
potent trough diving south out of Canada. Saturday will be a
seasonably warm day with highs in the 80s. Dew points in the middle
to upper 60s will make it feel a little on the muggy side but
overall is should be a rather nice late July day. The trough then
dives into the upper Mississippi River valley Saturday night into
Sunday bringing showers and thunderstorms to the area. A trough
then sets up across the region early next week with temperatures
expected to be below normal. Highs on Monday will be rather
pleasant...ranging from the lower to middle 70s. Weak disturbances
moving through the region in the northerly flow will bring slight
chances for showers and storms towards the middle part of the


Aviation...(for the 06z tafs through 06z Thursday night)
issued at 1058 PM CDT Wednesday Jul 23 2014

The first aviation concern remains valley fog/stratus potential
at lse this morning. Some passing clouds during the evening caused
the temperature/dewpoint spread to hold up...still at 12 degrees
as of 03z. This is quite high and may be too high to allow for fog
formation at lse given the shorter night. Therefore...have
improved the visibility in the 11-13z tempo group to MVFR. On the
other hand...with the clouds now cleared out and clear skies
likely to continue...think there still is a decent chance of an
LIFR stratus deck to form in the valley. Thus that continues in
the tempo group.

Next aviation concern is for the evening with shower and
thunderstorm potential. Warm and more humid air arriving well
above the surface...near 10000 feet...looks to erupt isolated-
scattered high based showers and thunderstorms. For now have
included only vcsh at both sites...but could see a thunderstorms in the vicinity need in
later tafs...especially at rst closer to 06z. Looking ahead to
after 06z...shower and thunderstorm chances will increase further
as a wave of low pressure moves into Iowa.


Arx watches/warnings/advisories...


Short term...wetenkamp
long term...wetenkamp

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