Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 162330

Area Forecast Discussion
National Weather Service La Crosse WI
630 PM CDT Fri Mar 16 2018

.SHORT TERM...(This evening through Saturday)
Issued at 300 PM CDT Fri Mar 16 2018

The main short-term forecast concern is a stacked low pressure
system centered over southern Nebraska/northern Kansas early this
afternoon. The low is forecast to drift to the east through tonight,
bringing precipitation into northeast Iowa and far southwest
Wisconsin during the evening and overnight hours. While QPF totals
should remain fairly light (around 0.1" to 0.2"), precipitation
types will be challenging. First of all, HRRR/RAP soundings are
suggesting a saturated isothermal layer around 0 C from the surface
to at least 800 mb. Second, there is a strong signal that ice
nucleation will cease, especially along and south of a line from
Charles City, IA to Oelwein, IA. On top of all this, a very dry air
mass is entrenched within the boundary layer, which may cause a
delay of column saturation. In short, think the far northern edge of
the precipitation should remain mostly snow, with a mix or change
over to light freezing rain across our far southern areas during the
overnight. Due to the multiple factors playing into this event,
confidence is not high enough to issue a Winter Weather Advisory as
of this writing. Current forecast accumulations are for up to 1 inch
of snow and a few hundredths of an inch of ice. This will be enough
to make untreated surfaces slippery.

As the low departs to the east, high pressure will begin to build in
Saturday afternoon, leading to decreasing clouds, light winds, and
above normal temperatures.

.LONG TERM...(Saturday night through Friday)
Issued at 300 PM CDT Fri Mar 16 2018

Overall, a fairly quiet period of weather is shaping up through the
latter half of the weekend through much of next week. High pressure
will remain over the area Sat night into Sunday with dry and
seasonably mild conditions.

Models are in good agreement taking an upper trough across the Mid-
Mississippi Valley Monday into Tuesday with the bulk of this precip
remaining south of the area. 12Z model guidance continues to
indicate additional mid/upper troughing and some light precip trying
to spread eastward from western MN/IA Monday night and Tuesday, but
very dry northeasterly low-level flow may inhibit much eastward
progress of any precip. Have continued to trend this period drier.

A tranquil stretch of weather is expected through mid-week with
surface high pressure over the area and seasonable temps. The next
shot at some precip looks to come next Friday or Saturday as an
upper trough emerges from the western US and surface low pressure
develops somewhere across the plains.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 630 PM CDT Fri Mar 16 2018

A narrow band of wintry precipitation from KFSD to south of KDBQ
as of 16.2330Z will remain south of TAF airfields through tonight.
Lower ceilings and visibility associated with this precipitation
will also remain south. BKN ceilings at KLSE/KRST will consist of
cirrus through Saturday morning before clearing in the afternoon.
Light easterly winds will be the rule for much of the period, but
are expected to diminish and turn to the north-northeast late
Saturday afternoon.




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