Special Weather Statement, NWS Quad Cities, IA

Area Forecast Discussion
National Weather Service Quad Cities IA IL
705 PM CDT Fri Oct 6 2017

...00Z AVIATION UPDATE...

.SYNOPSIS...
Issued at 325 PM CDT Fri Oct 6 2017

Warm front has lifted to about Highway 30 with a nice low level
moisture feed of PWAT's near 2 inches. The main upper level trough
was located in the Northern Plains and into Colorado with a series
of impulses moving through the Midwest in the southwest flow
aloft. Each disturbance brings a round of forcing and this has
caused an area of showers across much of the dvn cwa this
afternoon. Shear and instability is weak and have not noted any
lightning. However, on the nose of the low level jet and stronger
impulse in southern MN and northern IA there have been
thunderstorms and heavy rainfall.

In the dvn cwa afternoon temperatures were in the mid 60s to lower 70s.
Dewpoints were well into the 60s.

&&

.SHORT TERM...(This Evening through Saturday)
ISSUED AT 325 PM CDT Fri Oct 6 2017

Forecast focus on several rounds of showers and isolated
thunderstorms in the short term.

Tonight: There will be rounds of showers and isolated
thunderstorms moving northeast across the cwa, as individual upper
level disturbances enhance the forcing. In other words, there won't
be widespread rain constantly but at times the rain will be
scattered. The NAMNEST suggests this current batch of rain
becoming scattered this evening with more widespread rain later
tonight. I tried to adjust the pops based on the CAM's. This will
be a mild night with lows in the mid 60s.

Saturday: The main upper level trough/strong dynamics arrive with
the models indicating the trough going negatively tilted. This
should enhance the forcing as the cold front pushes across the
cwa, and low pressure tracks into WI. With the very moist air in
place there still remains the potential for locally heavy rainfall
late tonight and into Saturday. We still expect many locations to
receive 1/2 to 1 inch of rain, possibly up to 2 inches in spots.
Deep layer shear becomes moderate to strong, but instability is
very limited due to extensive cloud cover, so at this time not
expecting strong storms. However, it is interesting that the
NAMNEST shows a line of storms forming along and east of the MS
River in the afternoon, ahead of a narrow dry slot. Something to
monitor. As of now, SPC has a marginal risk well to our east into
MI and IN. Highs should range from the upper 60s to mid 70s. HAASE

.LONG TERM...(Saturday Night through Friday)
ISSUED AT 325 PM CDT Fri Oct 6 2017

The extended appears to be a mainly dry forecast, with several large
swings in temperatures, though it may be mainly dry with each event.
The Tuesday system, which had appeared likely to bring rainfall to
much of the CWA on the 00z runs is now much more disjointed in the
models, and with that both timing and system strength have been
degraded to the point of only low pops spread out over two days.
That's the one step before the blend removes the storm totally in
most cases, thus this week should be seen as pleasant Fall weather.

With southwest winds, Sunday should see highs back to the upper 70s.
For some areas that do not see more than a 0.10 in rain with the
current event, soils may be dry enough for locally lower 80s, but
that is hard to pin down, and upper 70s is a safer bet for now. This
warm weather lasts though Monday, followed by a trof passage and
cooler weather for Tuesday and Wednesday, where highs should mainly
be in the 60s, and lows in the 40s. Warm advection should spread
back over the region by Thursday, as the upper pattern begins to be
influenced by a broad ridge, resulting in mild plains air spreading
over the Midwest. Highs to finish out the week are expected to be in
the 70s once again, with overnight lows in the upper 40s to lower 50s.
ERVIN

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
ISSUED AT 649 PM CDT Fri Oct 6 2017

Periods of showers and isolated storms expected through Sat AM with
the passage of a frontal boundary.

Ceilings...
VFR to start at KBRL and expected to remain for much if not all of
tonight before lowering to MVFR Sat AM, then returning to VFR
during Sat PM with dry slot. IFR to MVFR at KCID, KMLI and KDBQ
expected to improve to high MVFR and VFR from south to north this
evening through 06z. Cigs then to return to MVFR and IFR with the
frontal passage and may improve to VFR at both KCID and KMLI Sat PM,
but likely to be no better than MVFR at KDBQ.

Precipitation...
Areas of showers and some storms this evening trending toward less
coverage late evening into the overnight, but then expecting widespread
coverage early Sat AM ahead of the front tapering off to scattered
nature late AM. Dry slot then may bring about a threat for a few storms
Sat PM 19z-21z vicinity of KDBQ-KMLI and east, while wrap-around showers
may brush northeast IA terminals.

Winds...
Generally S/SE 10-15 kts this evening, and with winds increasing above
40 kts around 2 kft agl with LLJ I have added LLWS mention at all but
KDBQ for mid evening into the overnight. Expect gusty south winds 15-25
kts to develop overnight into Sat AM with LLJ and ahead of front, with
winds eventually veering to WSW while staying gusty Sat PM.

Visibility...
P6SM outside of any precipitation and generally 2-5SM in any precipitation,
with the lower visibilities being found in the stronger showers and
any storms where low risk of visibilities around 1 mile.

&&

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

SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Ervin
AVIATION...McClure

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
436 AM CDT Fri Oct 6 2017

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-070945-
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-
436 AM CDT Fri Oct 6 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...TODAY AND TONIGHT

Isolated thunderstorms are possible across the outlook area today
and tonight. Lightning will be the primary hazard and severe
weather is not expected.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

There is a low chance for thunderstorms Saturday. The main threat
from any storm will be lightning.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today or tonight.

Uttech/Sheets

Special Weather Statement
National Weather Service Quad Cities IA/IL
713 PM CDT FRI OCT 6 2017

IAC011-019-055-113-070115-
Buchanan-Benton-Delaware-Linn-
713 PM CDT FRI OCT 6 2017

...AN AREA OF THUNDERSTORMS WITH HEAVY RAIN WILL AFFECT SOUTHERN
BUCHANAN... BENTON...WESTERN DELAWARE AND NORTHERN LINN COUNTIES
UNTIL 815 PM CDT...

At 708 PM CDT, thunderstorms were clustered near Urbana, or 7 miles
northeast of Vinton, moving northeast at 45 mph. Additional
thunderstorms were located further west over Tama, Marshall, Jasper
and Poweshiek counties also moving northeast.

Frequent lightning and torrential downpours can be expected with
these thunderstorms. The periods of heavy rainfall may lead to
ponding and standing water on roads, and also produced low
visibilities. If outside, seek a safe shelter inside a building
or vehicle until these storms have passed.

Locations impacted include...
Independence, Vinton, Manchester, Hiawatha, Robins, Belle Plaine,
Center Point, Urbana, Dysart, Central City, Palo, Shellsburg,
Newhall, Winthrop, Walker, Van Horne, Alburnett, Coggon, Keystone and
Quasqueton.

LAT...LON 4264 9133 4214 9136 4190 9230 4230 9230
      4230 9207 4239 9206
TIME...MOT...LOC 0008Z 245DEG 40KT 4225 9195

MCCLURE