Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 202353
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
554 PM CST Tue Nov 20 2018

.SHORT TERM...(Tonight into Thanksgiving Day)
Issued at 317 PM CST Tue Nov 20 2018

Who`s ready to deal with more clouds? That`s the theme of the
forecast heading into Thanksgiving Day, though we may sneak in some
sunshine sometime Wednesday. For now, however, last vestiges of
earlier much-deserved clear skies are evident across southern areas,
but with mid level clouds overtaking most other areas, ahead of yet
another northwest-flow shortwave working over western Lake Superior.
Weak surface response also noted working across the Big Lake, with a
trailing cold front sagging south through central Minnesota and on
track to work through our area this evening.

Currently watching an area of light precipitation working across
areas near I-94, with sufficient ice in the clouds per surface
obs/forecast soundings to support some very light snow.
Thankfully haven`t see much hint of any freezing drizzle, owing
mainly to larger temp/dew point spreads in place and lack of
deeper boundary layer moisture (really need ceilings near or below
1kft). As such, have removed mention for the late afternoon hours.

Any light snow should depart by 01Z at the latest, leaving more
lower stratus working south in the wake of the passing cold front.
That stuff looks to stick around into much of Wednesday, though
may increasingly become confined farther south with time given an
influx of high pressure/drier air from the north (still some mid
clouds possibly in play though). Warmer air aloft then comes
rushing in Thanksgiving Day, but in typical fashion, really
looking like that warming will go into the production of lower
stratus across much of the area, tucked beneath a stout inversion
with little room to mix out. It`s not even impossible there could
end up being some freezing drizzle risk once again for more of the
area into Thursday afternoon with hints per forecast RAOBs of
moisture depth increasing to around 1.5km with shallow lift
beneath the inversion and sharp drying aloft. Could end up being a
sneaky threat for a day with higher travel, though to be honest,
confidence remains quite low. Higher confidence is placed in
temperatures struggling beneath the lower clouds, with highs
continuing to trend colder, perhaps even holding near freezing in
some areas despite the substantial warmth aloft.

.LONG TERM...(Thursday Night through Tuesday)
Issued at 317 PM CST Tue Nov 20 2018

Let the active weather begin with several potential systems of note
heading into late week and the weekend. First up is a well-
advertised wave lifting northeast from the Four Corners area Friday
into Friday night. Notable northward surge of moisture (PWAT values
nearing 0.75 inches up this way) and push of deeper layer warm
advection ascent pretty much ensures it should precipitation
sometime later Friday into Friday evening per current trends. Still
appears we will see sufficient surface warming to preclude any
freezing or frozen precipitation with this round, though it is
interesting to note the ECMWF is cooler in its thermal fields, with
crude forecast soundings suggesting a shallower warm nose at 925mb
only around 1-2C, so not impossible there could be a little sleet
farther north.

Next feature of interest is a shortwave progged to dive from the
Pacific Northwest into the Central Plains later in the weekend,
possibly closing off before lifting north into the Great Lakes by
Monday morning. Still quite a bit of uncertainty regarding exactly
how that feature will unfold, but at the moment there does appear to
be at least some risk for wintry precipitation returning to parts of
the area for the latter half of the holiday weekend. Plenty of time
to let the details unfold over the coming days, but suffice it to
say this one bears watching with increasing guidance consensus
emerging the past 48 hours. High pressure looks to return with drier
weather into early next week, though again, we`ll have to see how
any possible closed low evolves through the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 554 PM CST Tue Nov 20 2018

After a period of VFR weather, things will change starting this
evening as a short wave and associated front move through the area.
MVFR ceilings will be spreading in early this evening as the wave
approaches and low level saturation increases. Hints in short term
models that conditions could worsen to IFR overnight as well,
especially just west and south of the area as front continues to the
south. Details to be worked out, but high pressure behind this could
break things back out on Wednesday.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...Lawrence
LONG TERM...Lawrence
AVIATION...Shea



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