Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 250518
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1218 AM CDT Fri Sep 25 2020

...06Z AVIATION UPDATE...

.SYNOPSIS...
Issued at 312 PM CDT Thu Sep 24 2020

MCS decayed to our north earlier today. However, attendant
shortwave trough continues progressing southeastward
across far northeast IA, far southeast MN and western WI.
New convection has formed within the past hour east of
Decorah, IA within close proximity to vort max. Meanwhile,
further south we`ve seen a narrow band of sprinkles and
brief showers shift across areas north of I-80 over far
eastern IA and northwest IL within zone of positive vorticity
advection. Earlier widespread stratus and some fog north
has evolved into a broken to at times overcast cumulus, which
has kept temperatures down a bit into the lower to mid 70s
near Hwy 20 corridor. Further south with increasing solar
insolation and gusty south winds temperatures have climbed
back to where they`ve been the past few afternoons... and into
the upper 70s to around 80 degrees.

&&

.SHORT TERM...(This Evening through Friday)
ISSUED AT 312 PM CDT Thu Sep 24 2020

Chance for a shower or storm will remain into this evening
for portions of northeast IA and northwest IL in closer
proximity to passing vort max. Thereafter, clearing skies.
Lows should be at or a bit warmer than those of this morning,
but still quite comfortable and mainly in the 50s with light
southerly winds.

Friday, we`re looking at another surge of warm advection on
breezy southerly winds, as the pressure gradient strengthens a
bit between high pressure to the east and a trough of low pressure
approaching the Northern Plains. This along with abundant
sunshine will push highs into the lower to middle 80s. We
could also see elevated fire weather conditions develop in
cured agricultural fields during the afternoon, mainly west of
the Mississippi River where the stronger wind gusts around
30 mph are likely. However, if surface dew points remain in the
lower 60s this could mitigate some of the threat.

.LONG TERM...(Friday Night through Thursday)
ISSUED AT 312 PM CDT Thu Sep 24 2020

Key messages:

1) Warm and windy on Saturday with record highs possible.

2) Rain chances Sunday and Monday.

3) Much colder by mid-week.

Details:

Saturday: Low pressure will be tracking across central MN into
northern WI. This puts the dvn cwa squarely in the warm and windy
sector of the storm system. Forecast soundings also indicate a
capped atmosphere which will suppress convection. 850 mb winds will
also be increasing to 50 knots so southerly wind gusts should reach
around 35 mph. Skies should be mostly sunny which will boost
afternoon temperatures well into the 80s, with a few spots around 90
depending on how deep the mixing will be. These readings will be
very close to record highs at some locations. (See climate section).

Saturday night through Monday: Cold front arrives Saturday night and
pushes to our southeast by Sunday. Models suggest a low pressure
system forming on the front with the potential for rain in our
southeast cwa, which would then carry over into Monday. The ECMWF is
more aggressive with widespread rain in our southeast half, while
the GFS keeps the bulk of the rain from central MO to central IL.
For now the grids have only chance pops. Highs will be cooler with
70s on Sunday and 60s on Monday.

Tuesday through Thursday: Models similar in developing a highly
amplified flow with a very deep trough in the central United States
with a full-latitude ridge in the West. The biggest change in the
models is to significantly deepen low pressure up by James Bay
instead of the Great Lakes. Nonetheless, a much colder airmass will
be plunging southward into the Midwest, along with the potential for
windy conditions and instability showers. Temperatures will be a
challenge as the National Blend of Models indicate highs in the mid
50s to lower 60s, despite 850 mb temperatures of 0c or even negative
numbers. However, this appears to be based on sunshine. A stratus
overcast seems more likely with a cold pool aloft and cyclonic flow.
This cloudier scenario would make highs lucky to reach 50 degrees!

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1218 AM CDT Fri Sep 25 2020

VFR conditions are expected throughout. There is a low potential
for ground fog toward sunrise at DBQ and CID. Forecast confidence
is not high enough to include any mention at this time.
Otherwise, south winds will increase and become gusty from 10 to
20 plus knots in the late morning and afternoon hours on Friday.

&&

.CLIMATE...
ISSUED AT 312 PM CDT Thu Sep 24 2020

Record Highs for September 26...

Moline.........90 in 1891
Cedar Rapids...87 in 1998
Dubuque........89 in 1891
Burlington.....95 in 1897

&&

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

$$

SYNOPSIS...McClure
SHORT TERM...McClure
LONG TERM...Haase
AVIATION...Sheets
CLIMATE...Haase


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