Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 272350
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
650 PM CDT Tue Jun 27 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 338 PM CDT Tue Jun 27 2017

Clear skies, seasonably cool temperatures and dry air prevailed
this afternoon under retreating surface high pressure and mid
level subsidence. Subsidence was enhanced by a shortwave ridge
over the Central Plains, while further upstream, a shortwave was
producing was evident on water vapor imagery and area radars over
the Northern Rockies. Under this shortwave ridge, a returning low
level southerly flow has recovered dewpoints into the 60s, which
will spread eastward and replace the 40s over the local area by
this time Wednesday.

&&

.SHORT TERM...(This Evening through Wednesday)
ISSUED AT 338 PM CDT Tue Jun 27 2017

Focus remains on developing convection late tonight, which
commences a active period of weather through the rest of this
week. Severe storms and heavy rainfall will be a threat beginning
Wednesday. Tonight, an MCS developing over the plains will be
approaching the forecast area out of central and northern IA by
sunrise. Convective allowing models suggest at least isolated
showers and thunderstorms may develop ahead of this feature on a
developing 40 to 50 kt southwesterly low level jet. For now, have
pops centered mainly on the timing of the leading edge of this
complex, reaching into eastern IA by 3 am, then the MS river and
northwest IL by sunrise. The main threat from these storms would
be gusty winds, small hail and heavy rainfall. Have likely pops by
mid morning across the north, where the MCS will likely have the
greatest intensity before a natural mid to late morning decaying
mode.

Although synoptic forcing will be weaker during the day with a
possible weaker, convectively induced vort max moving across the
south, the lingering outflow boundaries and recovering instability
will keep a threat of storms, possibly severe through the
afternoon with large hail and damaging wind the primary threats.
SPC has maintained a slight risk over the entire area for Wed into
Wed night. Temperatures will likely recover well into the 80s.

.LONG TERM...(Wednesday Night through Tuesday)
ISSUED AT 338 PM CDT Tue Jun 27 2017

Several rounds of severe storms are possible from Wed night
through at least Friday morning, when a cold front moves through
and brings an airmass change. SPC maintains a slight risk over the
southern half of the forecast area in day 3 for Thursday, where
the warm front will likely lay out in a west to east fashion to
interact with impulses in the fast upper level flow. Outside the
severe threat with all modes of severe weather possible, there
will also be a threat of heavy rainfall due to moisture pooling
that pushes the precipitable water to well above 1.5 to possibly
near 2 inches by Thursday evening.

The rest of the forecast has periodic chances for what would
likely be non-severe storms with temperatures trending near to
perhaps a bit below normal through the middle of next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
ISSUED AT 644 PM CDT Tue Jun 27 2017

An active weather pattern is now set up to bring very strong
southwest winds aloft overnight, followed by a round of morning
thunderstorms which will move east from central Iowa to northern
Illinois during the 10Z to 18Z time frame. Heavy rain and gusty
winds are possible with these storms. Another round of storms is
possible later Wednesday afternoon and evening, but the coverage
of storms is less certain and will not be included in TAF
forecasts yet. For the winds aloft overnight, LLWS is included in
the pre dawn hours of all forecasts.

&&

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

$$

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


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