Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 062330

Area Forecast Discussion
National Weather Service La Crosse WI
530 PM CST Tue Dec 6 2016

.SHORT TERM...(Tonight through Thursday)
Issued at 220 PM CST Tue Dec 6 2016

Concerns in the short term:

1) Cold air
2) Light snow chances north

1) A blast of cold, winter air on tap for the region - and probably
about time considering the rather mild late fall/early start to
winter. 850 mb temps still set to take a tumble with the passage of
the cold front from this morning...dropping from around -4 C at 12z
to -14 C by 12z Friday. Highs near 20 with lows in the teens Wed-Fri
still looking good. With persistent cyclonic flow suggesting more
clouds then not, it should keep overnight temps up a bit. That said,
if there is a night where more clearing takes place, lows would
probably be 5 to even 10 degrees colder - especially for areas with
snow pack.

In addition...its going to be blustery. Pressure gradient tightens
up for Wed-Thu...15-25 mph with higher gusts, especially open areas
west of the Mississippi. Wind chills in the single digits above and
below zero will result. Brr.

2) Cyclonic flow, cold air a loft and decent low/mid level lapse
rates will promote light snow chances for the next few days. The
better chances will surround a westward hanging trough (extending
off the departing low pressure system) which slowly sinks southward
to across the local area by 00z Fri. Locally, most of the light snow
chances will hold along/north of I-94. Amounts will
minimal...perhaps 1/2 to 1 inch of fluff through the period.
Expect scattered flurries south of these light snow chances.

.LONG TERM...(Friday through Tuesday)
Issued at 220 PM CST Tue Dec 6 2016

Main concern in this time period is the potential snow maker over
the weekend.

GFS/EC still on track with bringing and upper level shortwave west-
east across the Upper Mississippi River Valley this weekend. The
models also remain at odds with each other: placement, timing and
strength. Also, not a lot of continuity from run to run within the
models. Confidence moderate/high that snow will fall across the
region this weekend...but low in the details on where/when/how much.
GFS continues to lean stronger and thus more snow compared to the
EC. Some recent EC runs would keep the bulk of the accumulating snows
north of the local area. It certainly is a time period to watch.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 530 PM CST Tue Dec 6 2016

MVFR conditions continue at the moment along with periodic
flurries for both RST and LSE, though earlier blowing snow around
RST seems to be gradually settling down as much of the snow is
already well blown around. Those lower clouds look to depart over
the next 3-6 hours, leaving potentially a period of clear skies
overnight as winds remain gusty from the west. Heading into
Wednesday, lots of questions remain about how much additional
cloud cover will develop, but with continued cooling of the
column, suspect we will see additional MVFR stratus and/or
stratocumulus clouds develop, along with likely some additional




LONG TERM....Rieck
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