Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 122343

Area Forecast Discussion
National Weather Service Quad Cities IA IL
543 PM CST Sun Nov 12 2017


Issued at 230 PM CST Sun Nov 12 2017

Clouds lingered across eastern Iowa and Illinois during the early
afternoon hours as a mix of rain and snow pushed east. A band of
moderate to heavy snow affected areas along and north of
Interstate 80 through the early afternoon. Despite the relatively
warm ground temperatures, it was snowing hard enough that some
locations saw a light dusting on grassy areas and elevated
surfaces. The highest amount reported was from Mount Carroll
Illinois, where a spotter measured a little more than half an
inch. The snow quickly melted off with little or no accumulation
on roads. Early afternoon temperatures were in the 30s to low 40s.


.SHORT TERM...(This Evening through Monday)
ISSUED AT 230 PM CST Sun Nov 12 2017

The main forecast issue of the short term period is timing of
clearing tonight, and potential for locally dense fog.

The Nam/Wrf 925mb RH prog has the current cloud field modeled
well, and clears out eastern Iowa by midnight, followed by western
Illinois shortly after. High pressure with a light or calm wind
will settle across the forecast area and with the recent rain/wet
snow, fog development is a good bet. Have mentioned the
possibility of some patchy dense fog in the updated Hazardous
Weather Outlook, with later shifts to monitor for specifics on
timing/coverage/intensity. Lows tonight will be in the 25 to 30
degree range.

For Monday, expect a quickly return to southerly winds with a
slight warm-up and highs area-wide in the 40s.

.LONG TERM...(Monday Night through Sunday)
ISSUED AT 230 PM CST Sun Nov 12 2017

Tuesday, expect dry weather with near normal temperatures as the
upper air pattern across the United States becomes zonal. High
temperatures will be in the upper 40s north of Interstate 80 with
highs in the low 50s south. Overnight lows will be near freezing
across the north and the upper 30s in the south.

Tuesday night and Wednesday morning, A 500 millibar shortwave moving
through the zonal flow aloft will push a surface cold front across
the forecast area. This system will bring a chance of showers and
perhaps a thunderstorm late Tuesday night into Wednesday morning.
Skies will clear Wednesday afternoon as this shortwave moves to the
east. Temperatures will be around 50 across the north with mid 50s
over the south. Lows Wednesday night will drop into the upper 20s.

Thursday, Mainly clear skies are expected as an upper level ridge
and surface high pressure builds over the region. High temperatures
will be in the 40s with lows in the 30s.

Friday and Friday night, Another upper level shortwave will move
across the region bringing a chance of rain Friday, possibly
changing to a mix of rain and snow on Friday night. Daytime high
temperatures will be in the 40s with overnight lows in the 20s.

Saturday and Sunday, Any lingering rain should end by mid day
Saturday with dry skies expected for the rest of the weekend. High
temperatures will be in the 40s with lows in the 20s. The upper air
pattern across the county will be changing as a deep trough digs
across the east and an upper level ridge builds over the
intermountain west.


.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
ISSUED AT 538 PM CST Sun Nov 12 2017

Skies will clear this evening as high pressure builds in. Overnight,
the combination of clear skies, near calm wind, and wet ground
will promote fog development with conditions deteriorating to
IFR with areas of LIFR/VLIFR through mid morning on Monday. Increasing
southerly wind should aid in fog lift by late morning through midday
with VFR conditions to dominate thereafter.




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