Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 161209

Area Forecast Discussion
National Weather Service Quad Cities IA IL
709 AM CDT Fri Jun 16 2017


Issued at 345 AM CDT Fri Jun 16 2017

Frontal boundary stretched across northern IA and an intensifying
low level jet and steep low/mid level lapse rates generated severe
convection during the evening across the dvn cwa. This convection
has gradually weakened since midnight and has become scattered,
but storms were still producing heavy rainfall and frequent
lightning. PWAT`s were around 1.6 inches.


.SHORT TERM...(Today and Tonight)
ISSUED AT 345 AM CDT Fri Jun 16 2017

Forecast focus on severe weather this evening.

Today: Current convection will continue to diminish and move out
of the cwa by early to mid morning, as the low level jet weakens
and veers westerly. Clouds will thin as the day progresses allowing
for sunshine and the heat/instability to build again this afternoon.
I do not see a trigger for convection this afternoon until late
in the day in the far nw cwa. Afternoon highs will push into the
mid to upper 80s, with dewpoints in the mid to upper 60s.
Thunderstorms should develop later this afternoon along the nearly
stationary boundary in northern IA.

Tonight: Low pressure will move into the central Plains with the
low level jet intensifying once again, providing low level
convergence and forcing. A speed max will be arriving at mid
levels with deep layer shear increasing. ESRL HRRR/NAMNEST
suggests storms organizing into bowing segments as they rapidly
push southeast/east across the cwa this evening, gradually
diminishing overnight. Damaging winds of 60 to 70 mph look to be
the main threats from these storms, along with torrential rain and
frequent lightning. SPC has a slight risk roughly near and west
of the MS River with an enhanced risk to our west. Lows will be in
the upper 60s to lower 70s.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 345 AM CDT Fri Jun 16 2017

Forecast focus on enhanced risk of severe storms on Saturday then
cooler and less humid Sunday into early next week.

Saturday/Saturday evening: A potent severe weather situation
appears to be shaping up for the afternoon and early evening
hours. SPC has an enhanced risk for much of the dvn cwa as a
deepening upper level trough/stronger cold front arrives. There
is the potential for a derecho or at least bowing segments forming
into a mature bowing squall line, along with possible spin-up
tornadoes (mesovortices). With the strong heating/instability and
mid level winds of 70-75 knots, there is the potential for 70-80+
mph very damaging winds. Highs will be in the 80s to lower 90s,
with heat index values in the mid to upper 90s, mainly south of
Interstate 80.

Sunday through Tuesday: Northwest flow aloft with cooler and much
more comfortable humidity levels. Sunday looks dry but there may
be a few instability showers or isolated storms on Monday. Highs
will be in the 70s to near 80, with lows in the 50s.

Wednesday through Thursday: Upper flow becomes zonal and thunderstorm
activity looks to increase once again. A strong warm front will be
pushing northward into the cwa setting the stage for an MCS
especially Wednesday night into Thursday morning. With dewpoints
rising back into the 60s, locally heavy rainfall is possible.
Highs will soar back into the 80s.


.AVIATION...(For the 12Z TAFS through 12Z Saturday Morning)
ISSUED AT 708 AM CDT Fri Jun 16 2017

VFR conds for much of today then thunderstorms will increase in
intensity and coverage this evening and gradually diminish
overnight. Some of the storms may produce damaging winds and heavy
rainfall. Expect MVFR/lcl IFR cigs/vis in/near thunderstorms.
Mainly south to southwest winds around 10 knots away from storms
through this taf cycle.




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