Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 161805
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1205 PM CST Thu Nov 16 2017

.SHORT TERM...(Today and tonight)
Issued at 319 AM CST Thu Nov 16 2017

Main forecast concerns in the short term are on cloud cover today
and chances for light rain/snow late this afternoon into tonight.

At 3 AM this morning we are currently watching an expansive area
of stratus across much of the upper midwest. We should start
seeing some breaks in the stratus by this afternoon as surface
high pressure slides through leading to partly sunny skies by the
afternoon hours. Strong 850-700 mb warm air advection moves over
the region from west to east this afternoon into this evening and
this may be enough to generate a few sprinkles or very light
snow. Forecast soundings are very dry below 5 kft so thinking much
of this won`t make it to the ground. We will see an increase in
mid level clouds with this feature and likely some mid level echo
on radar. Low level moisture increases across the region tonight
through Friday morning as a trough approaches from the west.
Light drizzle and stratus will overspread the region during this
timeframe, but the bulk of any drizzle should hold off until
after 12Z(6 AM) Friday.

.LONG TERM...(Friday through Wednesday)
Issued at 319 AM CST Thu Nov 16 2017

Main forecast concerns in the long term are on chances for
freezing drizzle and light ice accumulation Friday morning mainly
along and north of Interstate 94. Travel could be slippery Friday
morning.

Drizzle will be ongoing across much of the area Friday morning as
low pressure and an inverted surface trough move east across Iowa
and southern Minnesota. Have kept sleet out of the forecast for
Friday morning due to a dry layer between 6 and 12 kft. If this
dry layer can be overcome a light mix of sleet/freezing rain is
possible in addition to drizzle/freezing drizzle. Forecast models
are trending deeper with the amount of saturation so we may have
to switch the weather type back over to rain/freezing rain versus
the drizzle solution. Will keep as drizzle for friday morning with
with a switch over to rain Friday afternoon. Temperatures are
expected to warm above freezing across the forecast area by Friday
afternoon ending the threat for icing in the north. Light rain
should then continue into Friday night. A switch over to snow is
expected Saturday morning before the precipitation exits the area
as low pressure deepens over southern lower Michigan. Saturday
will be a windy day across the region with northwest winds of 15
to 20 mph with gusts to 35 mph possible.

A weak shortwave moves over Lake Superior on Sunday but locally
surface high pressure looks to remain in control with dry and cool
weather expected. Monday could be the warmest day ahead of the next
cold front set to move through the region Monday night. Highs on
Monday will range from the lower 40s over northern Wisconsin to
around 50 across northeast Iowa. Highs will then cool back into the
30s through at least Thursday. The next chance for snow arrives
Thursday night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1205 PM CST Thu Nov 16 2017

The main forecast challenge this period is timing the changes of
flight categories. The general idea is for MVFR ceilings to become
VFR by late this afternoon, a return to MVFR ceilings overnight,
and a lowering to IFR between late Friday morning and early Friday
afternoon. But the exact timing of these changes remains
uncertain at this point.

Expect the current trend of gradual clearing in the massive
stratus deck to continue through the afternoon, giving way to VFR
ceilings after 16.21Z. The question then becomes how quick the
MVFR clouds fill back in overnight. Thinking this could happen by
17.06Z, but these times will likely be adjusted in future TAF
issuances. There is also a potential for IFR ceilings to develop
at KRST overnight, which is reflected in the SCT008 group at
17.03Z. IFR clouds and drizzle are expected to build in from the
south late Friday morning into Friday afternoon. The switch to IFR
should occur at KRST first, so included in this TAF.

Southeast winds will gradually increase to around 10-15 kt through
tonight, with gusts to 25 kt possible at KRST.


&&

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

$$

SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION...Hollan



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