Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service La Crosse WI
315 PM CDT Tuesday Jun 30 2015

Short term...(this evening through wednesday)
issued at 315 PM CDT Tuesday Jun 30 2015

Primary challenges tonight include cloud trends/temperatures and
fog potential as surface ridge builds across the upper MS River
Valley. Will lean on latest high resolution model output for the
details.

Stubborn cumulus along and east of the MS River Valley finally
beginning to scatter out this afternoon and expect that trend to
continue this evening. Probably won't see completely clear skies
overnight with thick cirrus and some smoke from Canadian wildfires
likely to push into portions of the forecast area. Model guidance
also suggests some low stratus across Michigan moving into eastern WI
and these clouds could clip the eastern forecast area by 12 UTC
Wednesday. Some cloudiness combined with drier air mass (dewpoints
in the 40s) advecting into WI overnight will limit fog formation.
Still could see some patchy development in favorable low-lying
areas...but will keep it out of the grids for now and allow the
evening shift to re-evaluate. Temperatures tonight to drop into
the middle 40s to middle 50s.

Middle-level short wave will drop across the Central Plains on
Wednesday...but best forcing/moisture convergence will be well
south and west of the forecast area. With surface high pressure
firmly in place across the region...expect dry conditions with
periods of middle-high level clouds. Temperatures will be cool for
the 1st of July with afternoon highs only in the lower to middle 70s.

Long term...(wednesday night through tuesday)
issued at 315 PM CDT Tuesday Jun 30 2015

Primary challenge late this week...through the 4th of July weekend
and into early next week will be precipitation chances and temperatures.
30.12z global model suite in reasonable agreement and will use a
blended approach.

With upper level ridge across the western Continental U.S. And a broad trough
across the east...expect the upper MS River Valley to remain in
northwest flow into the upcoming weekend. Parade of short waves
in this flow regime expected to remain south and west of the
forecast area and with nearly stationary surface high pressure
dominating the regional weather pattern...expect dry conditions
through at least the 4th of July and possibly through much of
Sunday. Expect a gradual day-to-day warming trend...with highs in
the middle to upper 70s on Thursday rising into the upper 70s to
lower 80s by Saturday/Sunday.

Next best chance for showers and thunderstorms will be Sunday
night through Monday as a large eastern Pacific trough dives
across southern Canada and squashes the western Continental U.S. Ridge. This
should allow a frontal boundary to move across the forecast area
producing showers and thunderstorms. 30.12 UTC European model (ecmwf) is faster
with this system compared to the slower GFS...so some adjustments
in timing are likely. Way too early to determine severe risk at
this time given model timing differences...but a preliminary look
at severe parameters suggest that deep layer shear is too weak to
support severe convection. Should begin to see drying from west
to east by next Tuesday. Expect daily highs in the upper 70s to
lower 80s and nighttime lows in the upper 50s and 60s.

&&

Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1255 PM CDT Tuesday Jun 30 2015

Pesky clouds behind a cold front are lingering. Have pushed the
times back a bit more on that clearing...but MVFR or VFR clouds
are expected now. Clearing trend overnight.

&&

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

$$

Short term...Rogers
long term...Rogers
aviation...baumgardt

National Weather Service Glossary of Abbreviations