Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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889
FXUS63 KDVN 210520
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1220 AM CDT Sat Apr 21 2018

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 243 PM CDT Fri Apr 20 2018

Surface high pressure from the Great Lakes west into WI and southern
MN was providing a dry day over the region with sunshine and
temperatures edging closer to seasonable normals for this cool
April. At mid afternoon, temperatures were in the upper 50s and
to lower 60s with light winds. The dry airmass was limiting
dewpoints to the 20s, and even teens in a few locations, leading
to exceptionally dry relative humidity values in the 20 to 30
percent range.

&&

.SHORT TERM...(This Evening through Saturday)
ISSUED AT 243 PM CDT Fri Apr 20 2018

Dry and cool weather continues through Saturday as the surface high
shifts slowly eastward and is undercut by surface and upper level low
pressure moving out of the 4 corners region into the southern
plains. As the upper level ridge over the MO River Valley shifts
eastward, the axis of high cloudiness covering western IA will
progress eastward and thicken overnight. At the surface, this
setup will continue to supply the low level feed of dry easterly
winds into the forecast area through Saturday. The latest GFS and
WRF continue to depict light QPF associated with weak elevated
warm advection and frontogenesis across far northern IA possibly
reaching the IA highway 20 corridor late tonight into Saturday
morning. This looks overdone considering the weak lift and dry
air in place, supporting little more than virga and thus a dry
forecast is maintained.

The expected more widespread cloud cover tonight should hold more of
today`s daytime heating in place, resulting in warmer mins closer to
warmest guidance from the mid 30s north to lower 40s south. The same
clouds will then limit Saturday`s warming and thus maintained
highs from the mid 50s to around 60.

.LONG TERM...(Saturday Night through Friday)
ISSUED AT 243 PM CDT Fri Apr 20 2018

The slow day to day temperature moderating trend continues into
early next week. Conditions also look dry with the next rain
chances arriving Tuesday night, with intermittent chances through
Friday as a more active pattern returns.

Saturday through Monday: The area remains just beyond the northern
periphery of the slow moving surface and upper level lows moving
across the southern U.S. This will maintain the low level easterly
winds with daytime heating at least partially suppressed by high
cloudiness. The dry airmass and diminishing influence of the cool
high pressure departing to the east should lead to a continued
day to day warming trend with daytime highs consistently in the
60s Sunday and Monday, while lows hold in the upper 30s to lower
40s.

A cold frontal passage is maintained in the models for late
Tuesday, bringing chances for rain and a modest cool-down for
Wednesday. Thursday should warm back into the upper 50s and 60s
with low confidence chances for rain late in the day into
overnight due to the next cold frontal passage. A tight pressure
gradient that follows would lead to a breezy Friday with
temperatures held in the 50s and 60s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
ISSUED AT 1218 AM CDT Sat Apr 21 2018

Light east winds will continue through Saturday night, with VFR
conditions under high overcast clouds. Visibility will be
unlimited through the period.

&&

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

$$

SYNOPSIS...Sheets
SHORT TERM...Sheets
LONG TERM...Sheets
AVIATION...Ervin



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