Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 181722

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1222 PM CDT WED MAY 18 2016


Issued at 730 AM CDT Wed May 18 2016

As of 7 am, temperatures had warmed into the lower to mid 40s over
east central IA and NW IL with the full May sunshine. Thus, have
gone ahead and cancelled the frost advisory early. Also, early
visible satellite imagery shows only a small area of remaining fog
along the MS river between Fort Madison and Burlington. Otherwise,
visibilities have improved on surface observations and it should
no longer be an issue anywhere after 8 am. The forecast has been
updated for these trends.


Issued at 336 AM CDT Wed May 18 2016

A ridge of high pressure across the upper MS river valley and
central plains building south into the local area was providing
another cool spring night. This was resulting in temperatures mainly
in the 40s at 2 am with a couple sites in the upper 30s over east
central IA and nw IL. Dewpoints were in the lower 30s closest to the
high in the north, while mid and upper 40s were reported in the
south. Under mainly clear skies, radiational cooling was resulting
in some dense fog over s central IA, while pockets of fog in the 1
to 3sm range were developing along the MS river valley in SE IA and
far ne MO.


ISSUED AT 330 AM CDT Wed May 18 2016

Immediate short term focus centers on the on-going early morning
frost advisory across the far north, and the potential for fog this
morning across the south. With sunrise occurring before 11z this
time of year, any frost in the advisory area (Dubuque, Jo Daviess,
and Stephenson Counties), will likely burn off well before the 12z
expiration and will likely be able to cancel earlier. Across
southeast Iowa, northeast Missouri and adjacent west central
Illinois, have updated the forecast for early morning fog, which
will likely be most widespread in valleys and sheltered areas.
Light north to northeast winds, continuing to drive dryer air into
the region, should keep the fog rather shallow in nature and prevent
widespread dense fog. Any fog should quickly burn off within an hour
of sunrise.

Today and tonight, high pressure will migrate southeast into the
region while aloft the ridge axis from the Dakotas into western
Ontario builds eastward. There is a weak area of positive vorticity
over sw MN early this morning that rotates se through the area
during the day to provide weak lift. However, meager moisture should
prevent this front producing any more than virga. Looking at what
occurred upstream, and another day of deep mixing into a similar
airmass, highs should be in the mid to possibly upper 60s. Tonight
should be another clear and cool night with lows in the 40s. A few
upper 30s will again be possible in the coldest, sheltered sites in
far NW IL and east central IA, but the potential for frost looks
more limited than this morning and not mentioned. Also, near full
sunshine today should lead to further drying across areas of the
south that saw light rain the past couple days, and lead a lower
potential for fog.

.LONG TERM...(Thursday THROUGH next Tuesday)
ISSUED AT 336 AM CDT Wed May 18 2016

Thursday and Friday...Will side with the latest 00z run ECMWF
(although other models have trended this way as well) with both
broad upper ridging and upper MS RVR valley to GRT LKS sfc ridging
winning out and maintaining a dry fcst this period...effectively
shunting southern stream wave to the south. May just get some mid
and high level spill off clouds especially acrs the south half. More
days of deep mixing in very steep llvl lapse rates up above H8 MB,
making for highs Thu in the upper 60s to lower 70s...and more
widespread lower 70s on Fri with some sites pushing the mid 70s if
clouds off the southern stream system thin enough or don`t quite
make it up acrs the area.

Saturday and Sunday...latest run medium range model trends continue
to imply omega block pattern will reign acrs much of the mid CONUS
this upcoming weekend, making for a dry and thermally moderating
weather regime into Sunday. High temps finally back around normal
for both days, or even slightly above normal on Sunday.

Monday and next Tuesday...Longer range indications and ensembles
suggest upstream L/W trof acrs the western U.S. will make strides
eastward...with it`s lee-side southwesterlies interacting with
increasing warm moist conveyor up off the western Gulf making for a
convectively active plains to start the week off. The DVN CWA
should remain mainly dry during the day monday allowing warm air
advection/ increasing return flow to boost Temps to the upper 70s
or near 80 degrees in much of the fcst area. Southwesterly flow
sprawl and break down of the Omega Block will allow areas of
showers and thunderstorms to eventually feed acrs the local area
later Monday night and Tuesday. Broad mid and upper level ridging
developing from the lower MS RVR valley and eastward acrs the Gulf
states...while southwesterlies focus acrs the east central plains
into the GRT LKS could place the local area in a more convectively
active or even type of MCS track by the middle part of next week.


ISSUED AT 1220 PM CDT Wed May 18 2016

VFR conditions will be seen through 00z/20 as high pressure slowly
moves across the Midwest.


.DVN Watches/Warnings/Advisories...


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