Alert archive / Iowa / Special Weather Statements in 2019

Special Weather Statement, NWS Quad Cities, IA

August 5, 20195 counties in Iowa

NWS Quad Cities, IA issued this special weather statement at Aug 5, 2019, 10:37 PM CDT for 5 counties in Iowa. It was in force for 53 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Aug 5, 2019, 10:37 PM CDT (03:37 UTC)
Expired
Aug 5, 2019, 11:30 PM CDT
In force
53 min
Issued by
NWS Quad Cities, IA

Counties Cedar County, IA, Iowa County, IA, Johnson County, IA, Jones County, IA, Linn County, IA

The radar

The Quad Cities radar (KDVN), 97 km from the middle of the area, began a volume at 03:38 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 3.6 hours before the alert went out and 103 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Davenport, at 00:00Z on 2019-08-06Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 19 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Davenport, at 00:00Z on 2019-08-06The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 38 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
19 J/kg
Mixed-layer CIN
-176 J/kg
Mixed-layer LCL
1668 m above ground
0-6 km bulk shear
28 kt
0-1 km storm-relative helicity
38 m²/s²
0-3 km storm-relative helicity
93 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.1

Open this sounding in Storm Lab

The text

As transmitted.

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What forecasters said that day

The local office's own words before this special weather statement went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Quad Cities, IA wrote its last area forecast discussion before this special weather statement went out at Aug 5, 6:41 PM CDT, 3 hours 56 minutes earlier.

Area forecast discussion, Aug 5, 6:41 PM CDT, 3 hours 56 minutes before
Area Forecast Discussion
National Weather Service Quad Cities IA IL
641 PM CDT Mon Aug 5 2019

...00z AVIATION UPDATE...

.SYNOPSIS...
Issued at 301 PM CDT Mon Aug 5 2019

18Z surface data has a front running from the arrowhead of Minnesota
back into northwest Nebraska. Dew points were mainly in the 60s from
the Great Lakes into the northern Plains. Dew points in the 70s were
near the frontal boundary and across parts of the central Plains.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 301 PM CDT Mon Aug 5 2019

Satellite trends through mid-afternoon shows no vertical development
to the diurnal cumulus clouds over the area. When this is taken in
consideration with drier dew points the prospects do not look very
good for convection developing prior to sunset.

However I cannot completely rule out the possibility of a rogue
shower or thunderstorm developing before sunset.

Thus there is a much higher probability of very warm and dry
conditions through sunset.

Tonight there are two main scenarios in play. Scenario 1 is that
storms develop along the front and form a respectable band that
moves into the highway 20 corridor around sunset and slowly weakens
as it moves southeast through the area. Such a scenario would give
better chances for most areas seeing some rain.

Scenario 2 starts out similar to scenario 1 but storms fall apart
much quicker as they enter the highway 20 corridor resulting in dry
conditions for parts of the area.

Given the abnormally dry conditions across the area and the moist
bias in the models, scenario 2 does have merit.

What may happen is that a respectable line develops ahead of the
front and maintains itself through the development of a pool of cold
air as it moves into the area. If this occurs then areas generally
north of highway 30 would have the better chance of seeing rain
before a fairly quick weakening of the line occurs as it moves
southeast.

If the above situation does occur then there would be a risk of
damaging winds with the storms as they initially move into the area.

For Tuesday lingering showers and possibly a few storms will be seen
east of the Mississippi during the morning that slowly dissipates.
New storm development is then expected along the cold front by late
morning and afternoon for areas generally south and east of a
Sterling, Illinois to Kirksville, Missouri line.

.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 301 PM CDT Mon Aug 5 2019

Northwest flow is expected through the period with a couple chances
of precip a ridge riding waves come through the area.  Overall the
sensible weather looks to remain unchanged from the previous week.
Temperatures in the 80s and 90s with dewpoints in the 60s looks like
the norm through this period.  Plenty of sun will be expected.  A
few mornings will see temps in the low 60s and upper 50s otherwise
it looks like a repeat of last week.  The only change are the
chances for precip look to be more realistic.

The first chance for rain comes late in the week as a reinforcing
shot of cooler air moves into the area.  This front and associated
wave looks to cause scattered showers and storms across the area.
The next chance comes late in the weekend and into next week when
another front is forecast to sag through the area.  At this time,
none of these chances for rain look to do too much in the rain
deficit we currently have.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
ISSUED AT 635 PM CDT Mon Aug 5 2019

With pre-frontal southwest sfc winds and VFR level clouds, the
primary challenge for the TAF sites remains timing a line of
sctrd showers/thunderstorms in the VCNTY and acrs the airports
this evening and overnight. Extrapolating current movement of
storms upstream and using latest CAM timing, will generally keep
the timing windows of the previous 18z TAFs with the VCNTY and
TEMPO groups. Some storms may still be strong with gusty winds and
passing heavy downpours reducing VSBYs as they move acrs later
tonight. After the storm threat, a passing frontal system will
veer the winds to the northwest by Tue morning, with an increase
to 8-12 KTS by late Tue morning. There could be a 1-3 hour wind of
post-frontal MVFR clouds around dawn tue morning, but confidence
is low that the decks will be that low. Rest of Tue looks VFR with
showers mainly east of the TAF sites.  ..12..

&&

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

SYNOPSIS...08
SHORT TERM...08
LONG TERM...Gibbs
AVIATION...12
Hazardous weather outlook, Aug 5, 8:30 PM CDT, 2 hours 7 minutes before
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In the hours before

Special weather statement, Aug 5, 9:29 PM CDT, 1 hour 8 minutes before
Special Weather Statement
National Weather Service Quad Cities IA/IL
929 PM CDT Mon Aug 5 2019

IAC011-019-055-061-105-113-060315-
Buchanan-Dubuque-Benton-Jones-Delaware-Linn-
929 PM CDT Mon Aug 5 2019

...A LINE OF STRONG THUNDERSTORMS WILL AFFECT BUCHANAN...DUBUQUE...
NORTHERN BENTON...NORTHWESTERN JONES...DELAWARE AND NORTHERN LINN
COUNTIES UNTIL 1015 PM CDT...

At 925 PM CDT, radar indicated strong thunderstorms were located
along a line extending from near Colesburg to near Masonville to near
Elk Run Heights. Movement was southeast at 40 mph.

Winds gusts up to 45 mph are possible with these storms as they
approach.

Locations impacted include...
Dubuque, Independence, Vinton, Manchester, Asbury, Dyersville, Jesup,
Center Point, Cascade, Epworth, Farley, Urbana, Dysart, Peosta,
Central City, Fairbank, Edgewood, Winthrop, Hazleton and Earlville.

This includes Interstate 380 between mile markers 34 and 55.

Locally heavy rainfall is also occurring with these storms.

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

Persons in campgrounds should consider seeking sturdy shelter until
these storms pass.

LAT...LON 4238 9060 4203 9230 4230 9230 4230 9206
      4264 9208 4265 9096
TIME...MOT...LOC 0225Z 318DEG 38KT 4266 9112 4252 9162 4252 9226

12
Special weather statement, Aug 5, 10:18 PM CDT, 19 minutes before
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Local storm report, Aug 5, 10:25 PM CDT, 12 minutes before
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Special weather statement, Aug 5, 10:37 PM CDT, 0 minutes before
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The office that day

Everything else NWS Quad Cities, IA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 5, 9:29 PM CDTSpecial Weather StatementDVNBenton, Buchanan, Delaware, Dubuque46 min
Aug 5, 10:18 PM CDTSpecial Weather StatementDVNJackson57 min
Aug 5, 11:26 PM CDTSpecial Weather StatementDVNClinton, Muscatine, Scott49 min
Aug 6, 12:27 AM CDTSpecial Weather StatementDVNDes Moines, Henry, Lee93 min

Nearby

Special Weather Statements in Iowa, 2019Every special weather statement in 2019

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.