Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 191950
AFDDVN

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

.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 18Z TAFS through 18Z Monday Afternoon)
ISSUED AT 1236 PM CDT Sun Mar 19 2017

VFR weather will continue today, with gusty southeast winds at 10
to 20 kts. By this evening, increasing moisture along and ahead of
a low pressure system will bring scattered thunderstorms and a few
showers to locations mainly along and north of Highway 34 in Iowa
and western Illinois between the 05Z and 10Z period. After this,
there is potential for MVFR stratus development, and this could
impact much of Monday morning. For now, I have lowered CIGS to
around 3500 ft and will watch to see if post frontal stratus
threat is growing on satellite data.
ERVIN


&&

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

$$

SYNOPSIS...Ervin
SHORT TERM...Ervin
LONG TERM...Gibbs
AVIATION...ERVIN



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