Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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741
FXUS63 KDVN 180511
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1111 PM CST Sat Feb 17 2018

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 323 PM CST Sat Feb 17 2018

The upper level shortwave and associated quick burst of 1 to 2
inch snowfall was exiting into the western Great Lakes at mid
afternoon. At the surface, winds were turning northwest behind the
surface trough located roughly along the Mississippi River. A
surface high over the Dakotas will migrate southeast into the
forecast area under the progressive flow aloft, bringing a period
of quiet weather for the near term.

&&

.SHORT TERM...(This Evening through Sunday)
ISSUED AT 323 PM CST Sat Feb 17 2018

Main focus is on temperatures and potential for fog tonight, then
magnitude of warming Sunday as a strong warm advection return
flow develops in the wake of the passing high.

Low level moisture from the fresh snow cover and late afternoon
melting snow will enhance the likelihood for fog tonight as the
surface ridge passes between 06z and 12z. Will go initially with
"patchy fog" to "areas of fog" wording over roughly the northern
2/3rds of the forecast area, which appears most favorable for fog
formation. Mostly clear skies and fresh snow should allow enough
radiational cooling to reach guidance temperatures from the upper
teens north to mid 20s south.

Sunday: There may be some lingering fog over especially the east
and southeast until about mid morning, before surface winds
sufficiently increase and become southerly. For now, will have
the fog dissipating by 8 am, but this may be too early. Otherwise,
the tightening pressure gradient will lead to south winds at
least 15 to 25 mph by midday with associated mixing and warm air
advection to conservatively push temperatures to highs in the 40s
north to lower 50s in the far south .

.LONG TERM...(Sunday Night through Saturday)
ISSUED AT 323 PM CST Sat Feb 17 2018

Overview

Active weather pattern for the Midwest early in the week. Locally,
several rounds of precipitation are likely, some of which could be
moderate to heavy.

Monday

A warm front will lift northward through much of the forecast area
causing temperatures to rise into the 40s and 50s with 60s south of
I-80. There is uncertainty on how far north the warm front will make
it. The ECMWF is the warmest model. If the CMC/NAM/GFS continue with
the colder NE flow in the northwest forecast area, will have to
trend highs downward in that area.

Isentropic lift and significant 850mb WV transport will lead to
periods of showers and embedded thunderstorms through Monday night.
Forecast PWATs near 1.25 inches are highly anomalous at 3 standard
deviations above the mean for the middle of February. This amount of
moisture raises concerns for widespread rainfall amounts near and
over 1 inch. Areal flooding is possible due to runoff over frozen
ground. Additionally, break up ice jams could lead to some river
flooding.

Late Monday Night and Tuesday

As colder air filters in on NW winds behind a cold front,
temperatures are forecast to fall below freezing across the west and
northwest, which will lead to a period of freezing rain. The model
blend ice amounts of 0.10 to 0.25 inches west of a line from western
Dubuque County to Cedar Rapids to Sigourney seem reasonable at this
juncture. However, this ice forecast is subject to change since it
is days away. It`s also worth a mention that the freezing rain (and
possibly some sleet) may spread to the east toward the Mississippi
River into Tuesday afternoon and evening before it ends. Will have
to continue to monitor this period for potential winter headlines.

Wednesday

Drying out as the cold front shifts to our east. The ECMWF is an
outlier with widespread light snow moving in from the southwest for
Wednesday evening and night. For now, will keep forecast dry. Highs
will be slightly below normal.

Thursday on

Moderating temperatures to near or slightly above normal to end the
week. From Friday into Saturday, active southwest flow aloft will
likely bring more widespread precipitation into the area. Uttech

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
ISSUED AT 1108 PM CST Sat Feb 17 2018

Main concern is potential for dense fog and some low stratus
overnight, before southerly winds increase toward daybreak. Low
level moisture contributions from Saturday`s snowfall will mainly
impact KDBQ/KCID/KMLI overnight with periods of visibilities down
to a 1/4 to 1/2 mile. With southerly wind picking up near and
after 12z, am expecting conditions to improve more quickly than is
typical this time of year.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...Sheets
SHORT TERM...Sheets
LONG TERM...Uttech
AVIATION...RP Kinney



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