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Area forecast discussion
National Weather Service La Crosse WI
600 PM CST Wed Nov 20 2019

Short term...(this evening through thursday)
issued at 228 PM CST Wed Nov 20 2019

Latest water vapor satellite imagery shows upper level closed low
over the southwest United States and ridge over the central United
States. Pieces of energy ejecting out of the upper level closed low
is producing precipitation over eastern and central Kansas per
mosaic radar.

Tonight into Thursday...shortwave trough/energy ejecting out of the
closed upper level low will lift northeastward into the Great Lakes
region. With the increasing lift and moisture transport/convergence
over the forecast area this evening...rain is expected to overspread
the area and continue into Thursday morning. Precipitation type will
remain all rain...as temperatures profile will be well above
freezing. Models are suggesting system exiting quicker and moving
rain over forecast area faster. This would result in the possibility
of slightly lighter quantitative precipitation forecast amounts. Rainfall amounts are expected to be
seven up to an inch areawide. Latest hi-resolution models show
frontogenetical band to develop from north central Wisconsin to
southeast Minnesota where the potential of the heavier rainfall
amounts may occur.

Temperatures will remain mild tonight with lows dropping into the
middle 30s to lower 40s. The 20.12z deterministic models suggest
925mb temperatures warming to near plus 4 to plus 10 degree celsius
by 12z Thursday. High temperatures will occur in the morning hours
with highs climbing into the upper 30s to lower 50s. Surface cold
front is expected move across the forecast area by 18z Thursday and
cooler air will filter in late morning and afternoon. Expect
temperatures to fall during the late morning/afternoon hours and
drop into the upper 20s to 30s by early evening.

With the passage of the surface cold front...pressure gradient
tightens and winds will increase out of the west/northwest to 15 to
25 mph and gust potentially up to 40 mph.

Long term...(thursday night through wednesday)
issued at 228 PM CST Wed Nov 20 2019

After the system moves out by Thursday evening, high pressure builds
into the region, and seasonable temperatures return. Dry conditions
are expected through Monday.

Precipitation chances return on Tuesday next week. There is a lot of
spread between models and associated ensemble members, so
confidence is low on timing, precipitation type, and location.
General consensus is that a low pressure system could impact
somewhere in the Midwest sometime next week, including possibly
our forecast area. However, there are a few models that show there
could be little to no impact for the region. Given that
Thanksgiving is next week with plenty of people traveling during
that time, this period will be closely monitored. Keep up to date
with the forecast as it draws near.

&&

Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 600 PM CST Wed Nov 20 2019

MVFR conditions transitioning to IFR conditions are expected tonight
into early Thursday morning at klse and krst, with conditions
improving to MVFR by Thursday afternoon.

Low pressure will move quickly northeast into the area tonight,
bringing with it rain chances by around 6z at both taf sites. This
will bring MVFR ceiling and visibility reductions, with brief IFR
reductions to visibility possible in heavier rain. Ceilings will
lower later tonight under the rain shield, which will likely lead to
IFR ceilings at both krst and klse. Low level wind shear will also
be present ahead of the approaching low pressure system tonight with
southerly winds of 45 to 50 knots at about 2000 feet above the
surface.

As the system quickly moves east on Thursday morning, rain will end
by mid morning and ceilings should rise into MVFR range by
afternoon. With a tight pressure gradient on the back side of the
departing low pressure, northwest winds will be sustained at 15-20
knots with gusts in the 25-30 knot range before tapering off later
in the afternoon. Ceilings could rise into VFR by early evening,
but at this time confidence is lower and this was not included in
the taf yet.

&&

Hydrology...
issued at 228 PM CST Wed Nov 20 2019

Widespread 0.75 to 1.0 inch of rain is still expected tonight
into Thursday. While we have thawed several inches of ground
frost, the soil remains relatively wet and will not be able to
absorb much rainfall. This will result in Rising River levels,
though most, if not all, will remain in their banks.

&&

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

$$

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