Special Weather Statement, NWS Quad Cities, IA

Area Forecast Discussion
National Weather Service Quad Cities IA IL
305 PM CDT Fri Aug 28 2020

.SYNOPSIS...
Issued at 205 PM CDT Fri Aug 28 2020

A cold front stretches from northeast Iowa southwestward to near
KDSM to KOMA. Ahead of the cold front dewpoints were in the upper
60s to lower 70s with temperatures in the upper 80s to near 90
degrees. Surfaced based CAPE from 18z DVN sounding around 3300
J/KG but satellite and radar reveal capping still in place across
eastern Iowa, northwest Illinois, and far northeast Missouri with
warm air around 850 MB with a mixed layer CAPE around this
afternoon. Storms are forming along the front west of the area.

&&

.SHORT TERM...(This Evening through Saturday)
ISSUED AT 205 PM CDT Fri Aug 28 2020

The main concerns in the short term were chances of showers and
thunderstorms along with the severe potential. Models seem to be
moving be slower with the frontal passage today than observations
are revealing.

An unstable but capped environment is in place across the region
ahead of a cold front that will move across the area this evening.
Scattered showers and thunderstorm should be limited to along the
front as models do show the cap eroding with time late this
afternoon and into this evening. Model timing appears to be
slower than originally thought based on observations although a
secondary cold front is moving through northwest Iowa. Models show
lift and convergence increasing with time along the front late
this afternoon and this evening. The mixed layer CAPE along with
increasing deep layer shear of 30 to 40 knots along the front
means that their is a severe thunderstorm threat but the storm
coverage will be limited. Steep mid level lapse rates and dry air
aloft will allow for thunderstorms to produce hail over 1 inch in
diameter and potentially gusty winds. For this reason, the Storm
Prediction Center has a slight risk for severe thunderstorms
across the area.

Behind the cold front, expect clearing skies overnight with
falling temperatues and dewpoints. High pressure will move across
the region through the weekend with lower dewpoints and noticeably
cooler temperatures on Saturday. High temperatures will range from
the upper 70s to lower 80s.

.LONG TERM...(Saturday Night through Friday)
ISSUED AT 205 PM CDT Fri Aug 28 2020

The long term period begins Saturday night with a westerly to
northwesterly flow at 500 MB. Ridging will be in place across the
area during the day on Sunday while a disturbance passes to our
south across Missouri and into the mid South.

After Sunday, a disturbance passing to our north will push a cold
front across the area Monday into Tuesday with another chance of
showers and thunderstorms. Widespread rain is not expected with
the latest model runs showing a drier frontal passage.

A 500 MB upper level low digs southward into southern Canada
through the middle of the week which will dig a deep trough
across the eastern part of the CONUS. This will result in chances
of showers and thunderstorms Wednesday and possible and Thursday.
High pressure is currently forecast to build into the region
Thursday night into Friday.

Near normal temperatures in the upper 70s and lower 80s are
expected through the long term.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
ISSUED AT 1221 PM CDT Fri Aug 28 2020

A cold front will sweep through this evening, changing winds to
northwest and bringing a few isolated strong storms to the area.
Once the front moves through, dry weather is expected. Cumulus at
3000 to 5000 ft will continue to form through the heat of the day
today, before the front arrives, at this point, no overcast
conditions are expected. That said, a small cloud directly over a
ceilometer may falsely send out a special overcast sky condition.
The isolated storms today will have strong downburst potential,
and could contain hail as well as heavy rain.

&&

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

SYNOPSIS...Cousins
SHORT TERM...Cousins
LONG TERM...Cousins
AVIATION...Ervin

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
212 PM CDT Fri Aug 28 2020

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-291915-
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-
212 PM CDT Fri Aug 28 2020

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...THIS AFTERNOON AND TONIGHT

Isolated severe storms are possible from 5 pm to 11 pm across the
Outlook area, as a cold front moves through. The primary threats
are large hail and damaging winds. There is also a very low risk
for a tornado and minor flooding. The Storm Prediction Center has
placed the entire Outlook area in a slight risk for severe
weather.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

Thunderstorms are possible Monday. It is too early to determine the
potential for severe weather.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is possible late this afternoon and evening.

Special Weather Statement
National Weather Service Quad Cities IA/IL
313 PM CDT Fri Aug 28 2020

IAC019-282045-
Buchanan-
313 PM CDT Fri Aug 28 2020

...A STRONG THUNDERSTORM WILL AFFECT NORTHERN BUCHANAN COUNTY UNTIL
345 PM CDT...

At 310 PM CDT, a strong thunderstorm was located near Hazleton, or
near Oelwein, moving east southeast at 35 mph.

Winds in excess of 40 mph are possible with this storm. These winds
could cause weakened trees or branches to fall down. Half inch
hail is also possible.

Locations impacted include...
Independence, Fairbank, Winthrop, Hazleton, Lamont, Aurora, Stanley,
Winthrop Golf Course, Wapsipinicon Golf Course, Fontana County Park,
Littleton, Buchanan County Fairgrounds, Otterville, Jakway Park and
Fontana Park.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4264 9162 4242 9160 4251 9208 4264 9208
TIME...MOT...LOC 2010Z 287DEG 31KT 4259 9198

McClure

Special Weather Statement
National Weather Service Quad Cities IA/IL
321 PM CDT Fri Aug 28 2020

IAC055-282045-
Delaware-
321 PM CDT Fri Aug 28 2020

...A STRONG THUNDERSTORM WILL AFFECT NORTHERN DELAWARE COUNTY UNTIL
345 PM CDT...

At 320 PM CDT, a strong thunderstorm was located near Dundee, or 7
miles north of Manchester, moving east at 30 mph.

Winds in excess of 40 mph are possible with this storm. These winds
could cause weakened trees or branches to fall down. Half inch hail
is also possible.

Locations impacted include...
Manchester, Edgewood, Earlville, Greeley, Dundee, Oneida, Twin
Bridges Park, Petersburg, Backbone State Park, Delaware County
Fairgrounds, Manchester Airport and Coffins Grove Park.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

LAT...LON 4247 9121 4250 9160 4264 9160 4264 9121
TIME...MOT...LOC 2020Z 272DEG 25KT 4259 9148

McClure