Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 karx 131933 
afdarx

Area forecast discussion
National Weather Service La Crosse WI
233 PM CDT sun Oct 13 2019

Short term...(this evening through monday)
issued at 233 PM CDT sun Oct 13 2019

Local and regional radars this afternoon continue to show some
pockets of snow/rain showers over areas along and east of the
Mississippi River. These are mainly being driven by the steep low
level lapse rates and weak Omega in the cyclonic flow. Expect that
these will end early this evening as the boundary layer cools and
the lapse rates become less favorable. The next concern then
becomes when or if the clouds will clear out any overnight. Both
the 13.12z NAM and 13.15z rap show lots of low level moisture
trapped under the inversion in the cyclonic flow with the clouds
extending all the way back into the Dakotas. This low level
cyclonic flow really does not start to relax until very late
tonight across the southern sections as an area of high pressure
moves across Iowa. If this clearing does occur, still some doubts
whether is would occur early enough to allow for much frost to
form or for temperatures to drop much below freezing. With these
unknowns, do not plan to issue either a frost advisory or freeze
warning but will issue a Special Weather Statement to highlight
the potential. The clouds should then clear from south to north
through the day Monday as the area of low pressure over Ontario
continues to pull away from the region. With some sunshine, look
for warmer temperatures with highs in the 40s and lower 50s
expected.

Long term...(monday night through sunday)
issued at 233 PM CDT sun Oct 13 2019

Brief dry period will come to an end as a shortwave trough and
surface low/cold front move in for Tuesday. Rain chances increase
west to east Tuesday morning and continue into early afternoon. At
this time the greater amounts look to be to our north and east,
however, as the low becomes better organized after passing through
our area. With a small amount of cape (100-300 j/kg), there may be
some isolated thunder as well. Lingering wrap-around precipitation
may affect parts of western/north-central Wisconsin through the
evening, but should end by Wednesday as the low moves east.
Conditions will be cool wednesday(highs mainly in the 40s). The area
will be on the northern fringe of high pressure centered across the
Southern Plains for mid to late week, setting up a stretch of drier
weather through at least Friday afternoon. As the high drifts east,
southerly return flow Thursday and Friday will allow temperatures to
climb back up into the 50s and 60s. Next shot at rain comes
Saturday, as a shortwave moves across the area. Following this
system, models show upper level troughing and an area of low
pressure moving into the upper Midwest for Sunday/early next week,
but large placement and timing differences remain.

&&

Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1207 PM CDT sun Oct 13 2019

Visible satellite late this morning continues to show a large
expanse of cloud cover over much of the upper Midwest. Low level
moisture remains trapped in the cyclonic flow around the low over
southern Ontario. The 13.12z NAM and 13.15z rap shows this
moisture will remain over the area and even though the cyclonic
flow will be slowly weakening, expect the clouds to remain over
the area into Monday morning. Ceilings in this cloud deck are MVFR
and not expecting this to change overnight. The cyclonic flow
should weaken enough, along with drier air mixing, to allow the
clouds to scatter out and for VFR conditions to develop. There
could be some light rain or snow through this afternoon with some
steep low level lapse rates and will continue to include these
without any visibility restrictions. The winds will remain gusty
into early evening before finally dropping below 10 knots.



&&

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

National Weather Service Glossary of Abbreviations