Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 260821
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
321 AM CDT Sun Mar 26 2017

.SYNOPSIS...
Issued at 321 AM CDT Sun Mar 26 2017

Early this morning, the surface low pressure that has driven the
weather for the past few days was located over the southern CWA. A
warm front extended to the east across IL. Rain has been rotating
through the area this morning. The heaviest rain looks to have
fallen across the SW CWA. To the north and west of this low,
areas of dense fog have been reported. This low is forecast to
saunter north and east through the day today and serve as the
focus for the short term weather once again.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 321 AM CDT Sun Mar 26 2017

Main forecast concern for the short term are the chances for rain
today and again at the end of the period. The other concern is the
dense fog this morning across the area. Periods of dense fog will
be possible this morning. Rain will be possible through at least
early this afternoon today.

Question of when the chances for precip will end is the main
forecast issue. The HRRR keeps moderate precip around through at
least 18z today. Past 18z, hires guidance suggests some cellular
showers that move into IL by mid afternoon. Synoptic models keep
light QPF this afternoon. Current thinking is that the best chance
for rain will be before 18z and little to no chance for rain
between then and 00z.

Surface low should move across the area today as another upper
level wave and surface low is located right on the heels of the
current one. As the H5 wave ejects into the area, ridging will
keep temperatures warmer this evening and overnight. Guidance
brings QPF into the area between 06z and 12z Monday. As a result
have added schc and chc pops for this period.

As far as the fog goes, convergence along the sfc boundary has
led to dense fog on the cold side of this boundary. If the dense
fog becomes more entrenched in the area, may need a DFA.

.LONG TERM...(Monday through Saturday)
ISSUED AT 321 AM CDT Sun Mar 26 2017

On the heels of today`s low exiting the region, another weaker upper
low and surface low will sweep across Missouri Monday and Monday
night. This low is forecast to bring light rain over nearly all of
the CWA now, and with the stratiform nature of the light rain, pops
are now notably higher. This is not due to QPF, which remains a low
end forecast, under 0.25 for the most part. It will be another
cloudy, dreary, cool day, with highs possibly as cold as around 50
if rains begin early in the day, but will shade this a bit higher as
the main rain chance is later in the day and go with lower 50s north
to upper 50s far south.  Monday night, rainfall will quickly exit to
the east, with clouds lingering through the night. The clouds should
help keep most areas at or above 40 for lows.

Cooler high pressure is forecast for Tuesday into very early
Wednesday, with clouds thinning enough north that those seeking
sunshine may see a few hours north of highway 30 Tuesday. Otherwise,
clouds continue, especially in the south.

From this point on, the GFS and ECMWF(consistent on the last several
runs), experience what can only be described as irreconcilable
differences. While they both have another strong upper low exiting
the Rockies Tuesday, the GFS takes this wave well to the south,
while the ECMWF takes it up on a northerly track, over Missouri and
Iowa. From what I can tell, this major synoptic difference begins
with how the GFS handles convection. It explodes convection near and
south of the surface low in the southern states, and likely through
latent heat release, shifts the surface and upper low south and east
through the period, resulting in dry conditions over our CWA. The
ECMWF is bring the system, along with a wide swath of moisture rich
forcing northward over Iowa and all points south. The EC, which as
said is very stable from run to run, would bring another widespread
rain to the entire CWA Wednesday PM through Thursday night. Our
forecast is skewed toward the EC guidance, as we have lowered highs
Wed-Friday, and increased lows, accounting for what should be a
cloudy and very moist atmosphere. Needless to say, after that
system, the GFS and EC remain completely different synoptically and
a blended solution captures neither one.

ERVIN

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
ISSUED AT 1153 PM CDT Sat Mar 25 2017

Scattered showers will decrease in coverage overnight followed by
drizzle. Slackening winds, increased low level convergence, and
the lack of showers will allow dense fog and low stratus to
increase in coverage, with periods of VLIFR conditions.
Conditions will begin to improve during the late morning.


&&

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

$$

SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...Ervin
AVIATION...RP Kinney


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