Severe Thunderstorm Warning 169, NWS Quad Cities, IA

Area Forecast Discussion
National Weather Service Quad Cities IA IL
619 AM CDT Fri Nov 4 2022

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 359 AM CDT Fri Nov 4 2022

Dry conditions were observed across the region early this morning
ahead of a cold front. The cold front is presently making its way
eastward across central Iowa. Winds have shifted more northwesterly
behind the front. Current temperatures are remaining quite warm - in
the middle 60s, under cloudy skies.

&&

.SHORT TERM...(Today and tonight)
Issued at 359 AM CDT Fri Nov 4 2022

Key Messages...a more active weather pattern for the late week
begins today, with increasing chances of showers and thunderstorms
today into tonight. Heavy rainfall potential may lead to urban
flooding, especially in areas of clogged storm drains. Strong,
gusty winds are expected late tonight.

Our stretch of quiet conditions ends today, thanks to a cold front
that will make its way into the region later today. This front is
out ahead of a high-amplitude upper-level trough, situated over the
Intermountain West states. These features will gradually make their
way eastward, leading to more active conditions today into tonight.
The latest radar mosaic and surface observations indicate the cold
front is moving through central Iowa now, expecting to enter the
northwestern portions of our forecast area within the next hour or
so. Anomalously high moisture will be in place along the front,
with Pwat values progged around 1.3 to 1.5 inches today, which
would be record Pwat values for our region per the SPC sounding
climatology. Additionally, the NAEFS Pwat climatological
percentile anomalies show these values to be around 99.5 percent
of climatology, meaning extremely moist conditions! The HREF
localized probability matched-mean rainfall values through tonight
indicate a swath of 1 to 3+ inches of total rainfall, with the
axis of the heaviest rainfall progged over east-central Iowa.
Although our region continues to be in drought conditions, and
this amount of rainfall shouldn't result in any river flooding,
there is concern for some urban flooding, especially in areas of
clogged storm drains and plugged culverts due to fallen leaves.

In terms of strong to severe storms, the potential continues to be
very low, with meager instability in place. However, thanks to an
intensifying southwesterly low-level jet on the order of 45 to 55
knots, and 0-6 km deep-layer shear of 60 to 70 knots, I wouldn't
rule out some stronger wind gusts, especially in stronger cells
that form ahead of the front in the warm sector where low-level
lapse rates are more favorable. Along the front, it might be
tougher for any stronger gusts due to a low-level thermal
inversion that is progged to develop, which could make it
difficult for suitable momentum transport to the surface. SPC
doesn't have our region outlooked for severe weather, but you
don't have to go too far to get into the Marginal risk to our
southwest.

As we go into tonight, a very dynamic surface low is expected to
translate northeastward towards our region. This low should undergo
rapid intensification along the base of the aforementioned upper-
level trough, with plenty of upper-level support for rapid
cyclogenesis. Height falls of approximately 20 to 25 decameters are
progged by the 00.04 GFS and ECMWF, indicating a very dynamic
system. Further evidence of this includes the NAEFS MSLP
climatological percentile anomalies indicating a rapidly deepening
low, with MSLP values falling to 0.5 percent of climatology -
meaning a very potent low pressure system, even for this time of the
year! There is increasing concern for some rather strong south to
southwest winds as the surface low deepens, as the latest NBM v4.1
reveals probabilities of maximum wind gusts over 41 knots (~47 MPH)
over 60 percent for the eastern half of our forecast area Saturday.
We have trended the winds towards the NBM v4.1, which now has
wind gusts up to 50 MPH. Due to this, we have issued a Wind
Advisory for late tonight into Saturday morning, including all of
our Illinois counties, and the eastern tier of Iowa counties.
There is the possibility that a westward extension of the advisory
may be needed.

.LONG TERM...(Saturday through Thursday)
Issued at 408 AM CDT Fri Nov 4 2022

Key Messages...a very potent system will be moving through the
region early Saturday, bringing strong, gusty winds. Winds will
gradually start tapering off Saturday afternoon. Dry conditions
settle in for Saturday night through Monday night, with another
round of showers possible for Thursday into Friday.

Continuing on from the Short Term discussion above, winds will be
strong and gusty Saturday, as the potent area of low pressure
makes its way through the region. Model soundings all show
boundary layer mixing to around 850 hPa during the daylight hours,
with winds at the top of the mixed layer around 50 MPH. The
global models are all indicating a dry slot will develop over
portions of the region Saturday, but there remains some
uncertainty on the spatial coverage of the dry slot, so conditions
may dry out sooner than what we have forecast. Conditions will
gradually dry out later in the day Saturday, although some wrap-
around moisture could linger over our northern forecast area,
impacting northeast Iowa.

Zonal flow will gradually amplify into an upper-level ridge across
the central CONUS, leading to a stretch of dry conditions Saturday
night through Monday night. The next chances of precipitation
return for Thursday into Friday, with highs in the middle to upper
60s by mid week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 613 AM CDT Fri Nov 4 2022

The cold front is now making its way into our forecast area, which
will be a focus for a sudden wind shift and showers/storms. Ahead
of the front, we are seeing gusty south winds, with northerly
winds pushing in behind. Increasing moisture along the front will
support lowering ceilings to MVFR later on this morning, with
increasing chances of rain showers. As we go into the afternoon
hours today, ceilings are expected to lower further to IFR,
especially for the DBQ and CID TAF terminals. Some thunderstorms
will be possible in these areas this afternoon, with IFR
visibility reductions expected due to heavy rain and fog. Wind
speeds will increase through tonight and into tomorrow, with
southwest winds ranging between 10-20 KTs, gusting upwards to 40
KTs.

&&

.CLIMATE...
Issued at 255 PM CDT Thu Nov 3 2022

Record Warm Lows for Friday Nov 4th

Dubuque........54 in 1898
Moline.........58 in 1975

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Wind Advisory from 4 AM to 7 PM CDT Saturday for Clinton-Dubuque-
     Jackson-Scott.

     Wind Advisory from 1 AM to 4 PM CDT Saturday for Des Moines-Lee-
     Louisa-Muscatine.

IL...Wind Advisory from 4 AM to 7 PM CDT Saturday for Carroll-Jo
     Daviess-Stephenson-Whiteside.

     Wind Advisory from 1 AM to 4 PM CDT Saturday for Bureau-Hancock-
     Henderson-Henry IL-McDonough-Mercer-Putnam-Rock Island-
     Warren.

MO...NONE.
&&

SYNOPSIS...Schultz
SHORT TERM...Schultz
LONG TERM...Schultz
AVIATION...Gunkel
CLIMATE...Gibbs

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
422 AM CDT Fri Nov 4 2022

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-050930-
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-
422 AM CDT Fri Nov 4 2022

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

There is a chance of thunderstorms today into tonight. At this
time, the primary threat is lightning, although some locally
strong winds can't be ruled out.

Heavy rainfall is possible, which could result in ponding of water
on roads and low-lying areas, especially if storm drains and
culverts are clogged with leaves.

Strengthening southerly winds are expected late tonight into
Saturday, with winds gusting to around 50 mph, over northwestern
Illinois into extreme eastern Iowa. A Wind Advisory has been
issued.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

Strong, gusty south to southwest winds will continue through the
day Saturday, gradually weakening from south to north in the
afternoon.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today or tonight.

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