Hail in Iowa, March 19, 2017

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1148 PM CDT Sun Mar 19 2017

.UPDATE...
Issued at 1147 PM CDT Sun Mar 19 2017

As of 1145 pm, scattered elevated showers and thunderstorms were
rapidly developing from Marshalltown to Monticello, as predicted
by recent HRRR runs. Will be watching closely these for hail as
these trend E-SE along the edge of a field of MUCAPES exceed 1000
J/KG and nose of 50kt 850 jet over the next several hours. Have
adjusted pops toward recent RAP and HRRR runs through the rest of
the night, with the bulk of the precipitation likely east of the
area by sunrise.

&&

.SYNOPSIS...
Issued at 247 PM CDT Sun Mar 19 2017

A milder breezy day is taking place across Iowa and Illinois,
largely under sunny skies. However, mid level moisture is beginning
to advection northward, and the nose of this advection has been
producing a band of scattered showers and thunderstorms over
Missouri today, the northern end is moving through our far southern
counties as of 2 PM. This process will focus new storms over our CWA
tonight.

&&

.SHORT TERM...(This Evening through Monday)
ISSUED AT 247 PM CDT Sun Mar 19 2017

While coverage remains highly questionable, the chance that we will
have scattered storms appears certain tonight. The highest coverage
may be in the east half of the area overnight, but the chance exists
in all locations that elevated storms will fire. Movement should be
easterly, but the level of forcing is somewhat in question, thus the
band could set up in the north, and work south, or in the south and
remain south. Elevated instability is expected to be in the 1000 to
2000 CAPE range, and that is agreed on by nearly all guidance. The
deep layer shear should support updraft tilt, and with relatively
cold air aloft, it continues to support large hail occurring in the
stronger storms. Hail production should be easily done, and small
hail should be found in all storms tonight. The quarter size hail
may be far less common, and should result in only a few severe cells
around the 04Z to 08Z time frame. Lightning should be quite vivid,
as high cloud bases make for a long distance through clear air
before ground interaction.

Lows tonight should fall to the lower 40s north to the upper 40s
south.  For now, I have not introduced fog, but should clouds not
form as forecast after midnight behind the showers and storms, we
could see some fog formation in our Iowa counties. Monday morning,
any convection will quickly shift out of the eastern counties by 10
AM, followed by a mild day in weak cold advection. Highs are
continued to be forecast by guidance in the lower to mid 60s.

ERVIN

.LONG TERM...(Monday Night through Sunday)
ISSUED AT 247 PM CDT Sun Mar 19 2017

Main forecast concern for the long term are the chances for
precipitation late Monday and into Tuesday and then the chance for
precip again this coming weekend.  Tuesday, temperatures will be
warm enough for no accumulation of snow before turning all to rain.
The end of the week a deeper trof is forecast to move across the
area.  With this system there will be a greater chance for
precipitation along with possible thunderstorms.

Monday night into Tuesday, northwest flow will lead to a clipper
like system transversing the flow.  With the main vort max
orientated parallel to the flow, much of the forcing for any precip
will come from midlevel fgen areas.  With drier llvl fields, a
question of saturation comes into play.  Current blend has the
better pops with the passage of the H5 wave Tuesday.

Wednesday through Friday, the flow stays NW keeping the area cooler
than earlier in the week before ridging builds in and leads to a
warm up on Friday for the area.

This weekend, model consensus is that a large trof pulls out of the
four corners region into the central US.  Questions of timing and
moisture return leads to a lower confidence in when precip will
occur.  The flow is conducive to thunder, however moisture return at
this time is suspect.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
ISSUED AT 1147 PM CDT Sun Mar 19 2017

Developing scattered showers and thunderstorms will be possible
the next several hours at the CID and MLI terminals. Otherwise,
low level moisture convergence ahead of a weak low pressure system
passing through the area may result in areas of low clouds and fog
possibly into MVFR criteria late tonight into mid morning Monday.
Forecasts remain on the conservative side with mainly MVFR, but
will still monitor closely for the potential for more the
possibility of IFR as suggested by some short term models. All
sites are likely to be VFR by Monday afternoon with light north
winds as the system exits the region.

&&

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

UPDATE...Sheets
SYNOPSIS...Ervin
SHORT TERM...Ervin
LONG TERM...Gibbs
AVIATION...Sheets

Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
702 AM CDT Sun Mar 19 2017

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-201000-
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-
702 AM CDT Sun Mar 19 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

Scattered thunderstorms are expected tonight across most of the
Outlook Area, with the greatest coverage occurring from Midnight
into early Monday morning. Some severe storms are possible, with
the primary threat being large hail. The Storm Prediction Center
has placed most of the Outlook area in a marginal risk for severe
weather tonight.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

Late Thursday and Friday, a large storm system is expected to
produce scattered thunderstorms across the region. It is too
early to assess any severe risk at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed later tonight.

Special Weather Statement
National Weather Service Quad Cities IA IL
1207 AM CDT Mon Mar 20 2017

IAZ051>053-200715-
Benton-Linn-Jones-
Including the cities of Vinton, Cedar Rapids, and Anamosa
1207 AM CDT Mon Mar 20 2017

...THUNDERSTORMS WITH SMALL HAIL DEVELOPING OVER EASTERN IOWA...

At 1205 am CDT...National Weather Service doppler radar indicated
a line of thunderstorms from just north of Keystone through
Hiawatha to Monticello. These storms may hail up to the size of
dimes and frequent lightning as the move east to southeast
through 2 am.

When thunderstorms are occurring, move indoors. Do not stand by
windows. Avoid using telephones and electrical appliances until
the storm has passed.

Sheets

Special Weather Statement
National Weather Service Quad Cities IA/IL
1229 AM CDT MON MAR 20 2017

ILC073-131-200615-
Mercer-Henry-
1229 AM CDT MON MAR 20 2017

...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN MERCER AND SOUTHERN
HENRY COUNTIES UNTIL 115 AM CDT...

At 1227 AM CDT, a strong thunderstorm was located over Lynn Center,
or 10 miles west of Cambridge, moving east at 35 mph. Dime size hail
is possible with this storm over the next hour as it tracks across
southern Henry County.

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 4115 9044 4112 9044 4112 9048 4133 9051
      4133 9044 4136 9043 4142 8987 4115 8987
TIME...MOT...LOC 0527Z 262DEG 31KT 4127 9039

SHEETS