Special Weather Statement, NWS Quad Cities, IA

Area Forecast Discussion
National Weather Service Quad Cities IA IL
705 PM CDT Wed Jun 14 2017

.UPDATE...
Issued at 702 PM CDT Wed Jun 14 2017

The convection remains surface based, and is not supported
strongly aloft. Thus, the trend toward isolated coverage is
expected to continue, and the amount of surface based CAPE will
continue to decay, so intensities will generally decrease. Brief
flare ups are still possible, and will likely handle these with
SPS products if needed. The SVR watch will be left in effect only
int the far south, where the NE MO convection is still brushing
those counties. This threat is also on the decrease.

&&

.SYNOPSIS...
Issued at 330 PM CDT Wed Jun 14 2017

Water vapor loop indicating closed upper low rolling northeastward
acrs the SD/Canadian border region, with cyclonic southwesterlies
arching down toward the mid MS RVR Valley. Embedded vort max/MCV
noted in several surveillance imagery sources right acrs the local
area, and should exit off to the east and northeast by early this
evening. Other more upstream embedded vort max was located out
acrs the Neb panhandle. Otherwise, flow still on track to become
more westerly and progressive acrs the north half of the CONUS
into the weekend, putting the local area under almost a daily
chance for showers and thunderstorms through Sat night.

&&

.SHORT TERM...(Tonight)
ISSUED AT 330 PM CDT Wed Jun 14 2017

As the MCV exits to the east, it will take any lingering more
significant convection with it by late afternoon. But will have to
keep low to moderate CHC POPs for isolated to sctrd showers and
storms streaming up out of MO and acrs mainly the southeastern
half of the DVN CWA, ahead of the central plains wave and
lingering llvl convergence on lingering outflow boundaries. But
feel that there will be just a low chance that they will be strong
to severe, especially later in the evening. This activity should
wane too as the evening progresses and through midnight. Then, the
central plains upper short wave trof approaches late tonight for
a possible uptick in overnight and early thu morning convection
for isolated to sctrd showers/storms in the southern and
southeastern CWA, but marginal at best LLJ convergence make this
another low confidence call...only low chc pops warranted Lows
tonight in the 60s west of the MS RVR, to around 70 in the east.

.LONG TERM...(Thursday through next Wednesday)
ISSUED AT 330 PM CDT Wed Jun 14 2017

Thursday...Most of the day looks to be mostly sunny and dry, warming
to around 90 or lower 90s in most of the area but sfc DPTs mixed
down into the middle or lower 60s in the afternoon keep the Heat
Index in check. Then an approaching upper trof in progressive
westerlies, and arrival of a weak NNE-to-SSW oriented sfc front
pushing into the western CWA from central IA, may allow for isolated
to sctrd thunderstorms to POP up in central Ia and possibly make it
into the far west central and northwestern CWA By late afternoon.
Better support for more organized storm clusters or MCS activity
tomorrow night laying out to the south acrs KS into MO. Then 12z
models vary on another round of increased late night convection
especially south of I80 after midnight and into early Fri morning.

Friday...Various model solution outputs make for a muddled scenario
this day. What ever happens Thu night and lingers into Fri morning
convective debris-wise, will be a player in to what happens later in
the day. But most solutions suggest a diurnal decrease by midday,
and afternoon heating and destabilization into Fri evening. Then the
next upstream S/W will look to interact with an increasing LLJ with
THTA-E feed, which may allow for an MCS to develop acrs western IA
Fri evening, and come acrs the state overnight into Sat morning with
heavy rain and gusty wind potential.

Saturday and Sunday...Latest suite of medium range models continue
to suggest a stronger digging shortwave and sfc cold front may swing
acrs the region to produce another storm event late Sat and Sat
night, with strong forcing and vertical wind fields suggesting a
severe storm threat depending on instability build up earlier in the
day. A cooler, breezy day in store for Sunday behind the front.

Monday through next Wednesday...Longer range indications suggest
that GRT LKS troffiness will allow for a below normal temp regime
early to mid week. Some chance for isolated to sctrd afternoon
instability showers Mon and Tue, with a more organized shower chance
toward Wed depending on timing of a northwest flow clipper-like
system rippling down into the western GRT LKS.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
ISSUED AT 624 PM CDT Wed Jun 14 2017

Scattered thunderstorms will be possible the next few hours, and
radar trends are being used to decide TAF inclusion in storm
coverage. This places a threat into MLI, and a less threat into
BRL through 01-02Z. Otherwise, an isolated storm or shower remains
possible through tomorrow afternoon, but coverage is too low and
unknown timing to put into a TAF forecast. Outside of storms, VFR
conditions and light south winds will prevail. If any early
morning light fog develops, CID would be most possible as they
had rains fall there today.

&&

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

UPDATE...Ervin
SYNOPSIS...12
SHORT TERM...12
LONG TERM...12
AVIATION...Ervin

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
426 PM CDT Wed Jun 14 2017

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-151000-
Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson-
Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson-
Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll-
Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson-
Warren-Hancock-McDonough-Scotland-Clark-
426 PM CDT Wed Jun 14 2017

This Hazardous Weather Outlook is for portions of north central
Illinois...northwest Illinois...west central Illinois...east
central Iowa...northeast Iowa...southeast Iowa and northeast
Missouri.

.DAY ONE...LATE THIS AFTERNOON AND TONIGHT

Scattered severe thunderstorms will continue through 8 PM CDT
generally along and east of the Mississippi River and along and
south of the Interstate 80 corridor, and far northeastern
Missouri. The main threats with these severe storms continues to
be damaging wind and large hail, but an isolated tornado can not
be ruled out. The storms should weaken and move out of the area
after 7 or 8 PM CDT.

Hot and humid conditions will continue through early evening away
from the storms, with heat index readings as high as the mid 90s.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

There are periodic chances for thunderstorms Thursday night
through Saturday night.

For the first round Thursday night into early Friday morning, a
few strong storms are possible in the counties along and south of
highway 34. The main threats are strong wind gusts and lightning.

There is a marginal risk for severe thunderstorms on Friday
across the entire outlook area. The best chance for storms is
Friday evening or Friday night. Damaging winds and large hail are
possible with the strongest storms. Thunderstorm coverage will
likely remain scattered.

Strong or severe thunderstorms are possible Saturday afternoon
into Saturday night. However, confidence is low with respect to
timing and areal coverage. Please stay tuned to forecast updates
through this week.

.SPOTTER INFORMATION STATEMENT...

Storm spotter activation is currently needed this afternoon and
evening generally along and east of the Mississippi River, and far
northeastern Missouri.

12

Special Weather Statement
National Weather Service Quad Cities IA/IL
734 PM CDT WED JUN 14 2017

ILC015-085-IAC097-150100-
Jo Daviess-Carroll-Jackson-
734 PM CDT WED JUN 14 2017

...A STRONG THUNDERSTORM WILL AFFECT JACKSON COUNTY UNTIL 800 PM
CDT...

At 733 PM CDT, a strong thunderstorm was located over Springbrook, or
12 miles northeast of Maquoketa, moving northeast at 15 mph.

Pea size hail and heavy rain are expected with this storm.

Locations impacted include...
Bellevue, Preston, Hanover, Andrew, Springbrook, St. Donatus,
Spragueville, Green Island, Hurstville, Van Buren, Spruce Creek Park,
Blanding Landing, Whitton, Blanding, Cottonville, Reeceville,
Bellevue State Park, Camp Far Horizons and Smiths.

Torrential rainfall is also occurring with this storm, and may cause
ponding of water on roads. Do not drive your vehicle through flooded
roadways.

LAT...LON 4218 9012 4203 9041 4203 9047 4210 9070
      4238 9056
TIME...MOT...LOC 0033Z 225DEG 13KT 4214 9045

ERVIN

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