Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 251804
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
104 PM CDT Sat Mar 25 2017

.UPDATE...
Issued at 104 PM CDT Sat Mar 25 2017

At midday, the primary band of rain has lifted north of the
highway 30 corridor. The widespread low clouds and cool brisk
easterly flow was holding temperatures from the upper 30s to upper
40s. The exception was in the far southeast, where there was the
intrusion of the warm front that extended north and northeast from
the surface low in southwest Missouri. This boundary was roughly
south and southeast of a line from Putnam County IL to south of
Galesburg, into southern Hancock County. Temperatures were in the
60s in this warm sector, with a sharp contrast along the front, as
indicated by a noon temperature of 63 in Macomb, while Burlington
was 46. Visible satellite showed some thinning in the high clouds
in this warm sector, while area radars showed the next arcing
band of rain ahead of the nearly stacked low lifting north through
central MO.

High res and synoptic models have this boundary lifting only a
little further to the north, not likely reaching the I-80
corridor this afternoon before stalling as the surface low
advances northeast along the low level thermal gradient through
far southeast IA vicinity tonight. With building weak CAPE and low
level shear, will be watching for low top, possibly rotating
cells capable of hail in far northeast MO, extreme SE IA into
adjacent west central IL from mid afternoon through early evening.
Severe threat will be much more limited as any cells advance into
the increasingly deep stable airmass to the north.

The rest of the area will have little thermal recovery today with
temperatures holding in the 40s to lower 50s. Will be adding
widespread fog for the overnight, which may be dense, as is
typically favored along and north of the surface low track.

&&

.SYNOPSIS...
Issued at 330 AM CDT Sat Mar 25 2017

Early this morning, a slow moving upper level low was located over
the central United States. At the surface, a double barrel surface
low appeared to be forming over MO and OK. A warm front that moved
through the CWA late Thursday had pushed south into the area as a
cold front off of the Great Lakes. This cold front and surface low
will drive the weather in the short term period.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Sat Mar 25 2017

Main question in the short term period is how much rain will fall.
Guidance has been overdone in the total QPF so far across the
area. Went with superblend for QPF. With the low being cutoff
guidance usually has a hard time with correct solutions, this
leads to low confidence in the model QPF. However, there is little
question that the the best chances for precip are tied to the sfc
boundary across the area. This boundary will move north through
the day, along with it the best chances for precip. Overall
confidence in the forecast is low.

As mentioned previously, there is definitely a chance for low top
convection today underneath the H5 low. If breaks in the sky can
occur, there will be a better chance for convection. There is
chance for low level storm rotation, especially if some of the
convection can move with the sfc boundary as it moves north. Brief
tornadoes cannot be ruled out along the surface boundary. As the
storms move quickly into the cold side of the boundary, rotation
may increase, however the chance for tornadoes will decrease
markedly.

.LONG TERM...(Sunday through Friday)
ISSUED AT 330 AM CDT Sat Mar 25 2017

Sunday`s weather will be rather gloomy as the vertically stacked
upper low and surface low remain over the CWA through afternoon,
before moving off to the northeast as it continues to weaken. During
this process, areas of light rain showers will continue to be
possible. Rainfall should be rather light, but some isolated showers
will move rather slow, so isolated amounts over 0.25 are possible.
Temperatures and dewpoints will be closely tied to each other so it
will be springlike with light winds.

The low will move off Sunday night, only to be followed by another
push of moisture from the next low approaching the Mississippi
Valley. For now, it remains possible that this will bring rain to
the south half of the CWA Monday and Monday evening, but amounts
look very light and this could be a cloudy period if the storm drops
any farther south.

Tuesday and Tuesday night are confidently dry and at least some
decrease in clouds.  By Wednesday, models are differing on the
arrival time of the next system. The model blend brought in pops to
the southwestern counties as warm advection begins, but this is a
very low confidence forecast.  The ECMWF remains the most bullish on
the northerly track and stronger strength of the later week storm
system, while the operational GFS is farther south with the system
and has our region mainly impacted by dry northwest flow. For now,
the extended is biased towards the more stable ECMWF run.
ERVIN

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
ISSUED AT 104 PM CDT Sat Mar 25 2017

Widespread IFR conditions will remain in place this afternoon
through Sunday morning as a surface and upper level low pressure
system passes through the region. With the surface low moving
over southeast Iowa tonight, widespread low clouds and fog are
likely with IFR to LIFR conditions likely. A few showers and
thunderstorms are likely across southeast IA from late afternoon
through evening, which is mentioned as just showers for now.
Elsewhere, forecasts are trended with IFR to LIFR by tonight due
to low clouds and thickening fog with periods of light rain or
drizzle. Current timing of the system suggests little improvement
will occur by midday Sunday.

&&

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

$$

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



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