Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 162045
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
345 PM CDT Wed Aug 16 2017

.SYNOPSIS...
Issued at 330 PM CDT Wed Aug 16 2017

18Z surface data has a warm front just north of I-80 with low
pressure in western Iowa. Across Missouri a squall line was moving
toward the east. Dew points from the Great Lakes into the upper
Midwest were in the 60s. Near and south of the warm front, dew
points were in the 70s.

&&

.SHORT TERM...(This Evening through Thursday)
ISSUED AT 330 PM CDT Wed Aug 16 2017

Through late afternoon convection will continue to develop and
increase in areal coverage north of highway 30 as forcing associated
with the warm front moves into Wisconsin. South of highway 30
isolated showers and storms are expected.

The question is what happens from roughly 6 PM to midnight.

Satellite trends show little in the way of cloud development from
central Iowa back into northwest Missouri. Satellite does show a
nice push of dry air aloft moving into western Iowa from eastern
Kansas. However, the better instability and forcing will be from
Kansas into Missouri.

What may happen is that another organized line of strong convection
will move east across Missouri that slowly develops northeast into
eastern Iowa. Recent trends with the RAP suggests this scenario. If
this scenario occurs, the overall severe risk would be low as storms
across Missouri take advantage of the stronger forcing and greater
instability.

After midnight, the cold front will sweep through the area. Rain
behind the front decrease in coverage with time through sunrise
Thursday.

On Thursday, wrap around clouds will be over much of the area during
the morning and slowly exit the area during the afternoon. Any
lingering rain will become more spotty during the morning hours with
only isolated showers expected over the northeast third of the area
during the afternoon.

Temperatures Thursday will be highly dependent upon cloud cover.
Areas north of highway 30 may spend much of the day in the 60s
before popping into the mid 70s late in the afternoon with clearing
skies.    ..08..

.LONG TERM...(Thursday Night through next Wednesday)
ISSUED AT 330 PM CDT Wed Aug 16 2017

Thursday night and Friday...Wrap around stratocu to clear off to the
east Thu evening, with incoming sfc ridge lobe and seasonably cool
night in store. Lows in the low 60s and more coverage in the 50s. As
for Friday, most of the 12z model runs have continued to be more
progressive with vigorous digging short wave in northwest upper
flow, with the potential for sctrd showers and a few storms spilling
into the western/northwestern CWA by late Fri afternoon. The prime
lift window with this passing upper wave now appears will be from
00z-06z Sat, wiht the chance most any precip this feature kicks up
will be east out of the local area by early Sat morning. Thus sctrd
showers and some storms moving acrs portions of the area Friday
evening and into the overnight. Interaction with lift from this
system and a more pronounced moisture convergence/THTA-E feed will
look to occur on this systems southwestern flank to generate more
significant storm clusters or even a MCS type feature, from the
MO RVR Valley southward into KS and western/central MO Fri
evening.

Saturday and Sunday...In the wake of the Fri night system, latest
suite of medium range model runs generally suggest a fair weather and
warming period for most of the upcoming weekend. High temps by
Sunday with adequate return flow, may warm well up in the 80s, with
a few guidance solutions even suggesting some 90 degree readings
possible along and south of I80. Now looking at the Sunday night MCS
generation area potentail, the 12z ECMWF has the southerly warm
moist conveyor converging upon a boundary acrs the Dakotas, with
resultant storm cluster or MCS propagating eastward acrs MN into
early Mon morning. The 12z GFS maintains a further south mode with
initiation acrs Neb and the MO RVR Valley, but keeps it festering
out to the west through 12z Monday.  Just low chance POPs warranted
for now in the western CWA for late Sunday night, with a bias that
maybe the further south MCS spawning grounds of the GFS may be more
in line.

Monday through next Wednesday...Latest GFS and ECMWF runs suggest
the eclipse day Monday may be hot and humid in the upper 80s to
lower 90s acrs much of the area. Latest MCS generation and
propagation paths out of Sunday night may not be as impactful acrs
the local area with respect to debris clouds...but still way too
early to determine those kind of details for that far out at this
point. Could see where either an MCV or outflow boundary from
earlier upstream convective complex activity becomes the focus for
renewed thunderstorm development in or close to the local area later
Monday or Monday evening. Long range progs then suggest another
digging upper trof acrs the northern plains and upper MS RVR Valley
to interact with a warm moist feed up off the Gulf, and possible
southwesterly tentacle of monsoonal influence, to fuel strong
thunderstorms complexes acrs portions of the upper Midwest(including
the local area), Monday night into Tue. Then, for a secondary day in
a row, decent longer range agreement of the various medium range
models in shunting the active storm track to the south of the region
to the southern plains and OH RVR Valley by mid next week. Canadian
high pressure will then look to take grip of the region with cooler,
drier, and less humid weather for the mid to late next week
period.    ..12..

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
ISSUED AT 1241 PM CDT Wed Aug 16 2017

First wing of precipitation will slowly move through eastern Iowa
and northern Illinois through 00z/17. Areal coverage of convection
will increase through sunset. MVFR conditions will slowly
overspread eastern Iowa and northern Illinois through 00z/17 with
the potential for IFR conditions in TSRA. After 00z/17 widespread
MVFR conditions will be seen with SHRA/TSRA as a cold front sweeps
through the Midwest. Wrap around clouds close to 1 kft AGL are
expected to affect KCID/KDBQ and possibly KMLI after 11z/17.

&&

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

$$

SYNOPSIS...08
SHORT TERM...08
LONG TERM...12
AVIATION...08



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