Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 karx 182350 
afdarx

Area forecast discussion
National Weather Service La Crosse WI
650 PM CDT Fri Oct 18 2019

Short term...(this evening through saturday)
issued at 212 PM CDT Fri Oct 18 2019

Seasonably mild temps in the upper 50s to mid 60s were found
across the area as of 2 PM with gusty southerly low-level flow.
These south wind events are typically not efficient for producing
widespread higher end wind gusts as veering warm advection
vertical wind profiles tend to limit mixing depth. That said, with
900 mb winds late this afternoon increasing to around 50 kts,
some 40+ mph gusts are possible across open areas of southeast
Minnesota/northeast Iowa where a Wind Advisory remains in effect. Winds
will likely remain gusty even into tonight, especially for favored
wind prone areas across the west.

A weak cold front will translate across the region overnight tonight
into Saturday. Initially, a relatively dry atmosphere will limit
rain chances, but expect moistening to occur as the boundary
slides east. Consensus is for a band of showers to develop and
increase from the west late tonight and Saturday with up to around
1/4 to 1/3 inch of rain possible from parts of northeast Iowa
through western WI. Did trend the onset of rain and eastward
progression a few hours slower based on recent high res model
trends. Temps on Saturday will be coolest over portions of
central/southwest WI where showers/clouds stick around longer
(low/mid 50s) with some 60s farther west as clearing spreads
eastward behind the front.

Long term...(saturday night through friday)
issued at 212 PM CDT Fri Oct 18 2019

Attention quickly turns to a strong upper trough crossing east of
The Rockies Saturday night into Sunday. Increasing clouds are
expected Sunday with strengthening warm advection as transient
surface high pressure passes to the east. As a result, Sunday looks
like the better weekend day for outdoor plans for much of the
region with dry and mild weather and highs near or above 60 for
many areas.

A deep, closed upper low will slowly move across the upper Midwest
early next with a surface low passing from the northern plains
towards Lake Superior Sunday through Monday. A slug of moisture
transport/warm advection will lead to increasing showers and
isolated storms Sunday night into Monday followed by potentially
some lingering showers later Monday into Tuesday with the trailing
deformation zone as the surface low pulls to the north. Gusty
westerly winds will follow behind the low later Monday/Tuesday.

Northwest flow aloft will occupy the region for the mid and latter
stages of next week behind the early week system. Significant model
spread exists concerning the evolution of possible amplification
of a shortwave trough diving southeast within the flow later next
week and associated precip potential. For now kept only low
precip chances for mid to late week. Other than perhaps a brief
upward bump in temps on Wednesday, the trend for next week temp-
wise looks to be downward into the 40s for highs by late week.

&&

Aviation...(for the 00z tafs through 00z Saturday evening)
issued at 648 PM CDT Fri Oct 18 2019

Gusty southeast winds at the surface will diminish in intensity this
evening as daytime mixing ceases, but gusts of 25-30 kts will
still remain possible at rst for the next several hours. Even as
surface winds slowly relax a bit, a strong low level jet will
slide overhead this evening at a height of around 2000 feet. This
will lead to more than 30 knots of low level wind shear at lse, but rst not
expected to have low level wind shear issues due to lingering stronger surface
winds there. Low level winds will diminish late tonight as the jet
weakens and departs, with light winds turning SW to west on Saturday
as a cold front slips through.

That front will bring a line of mostly light showers through the
area Saturday morning, likely arriving around or just before
daybreak. Not expecting much impact on visibilities. There will be
a lowering cloud deck tonight, with a band of mid-level clouds
already developing just out ahead of the front across central
Minnesota. There are hints of a possible period of MVFR ceilings
as the front pushes through lse, less likely at rst. Expecting to
see an improvement to broken mid level clouds behind the front,
then scattering out through the afternoon.

&&

Arx watches/warnings/advisories...
WI...none.
Minnesota...none.
Iowa...none.
&&

National Weather Service Glossary of Abbreviations