Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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423
FXUS63 KDVN 260456
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1156 PM CDT Sat Mar 25 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 325 PM CDT Sat Mar 25 2017

Stacked low pressure system was located over south central MO at 2
pm. Temperatures were in the 60s and dewpoints in the 50s in the
mostly cloudy warm sector across eastern MO and much of IL up to
the now nearly stationary warm front reaching into our far
southeast counties. Surface reports and high resolution visible
satellite imagery showed this boundary was roughly from just south
of Princeton IL west to near New Boston and south-southwest along
the MS River into northeast Missouri. North and northwest of the
boundary, there were extensive low clouds. brisk northeast winds
and temperatures in the 40s. A weakening axis of rain and drizzle
was lifting north along the highway 20 corridor.

&&

.SHORT TERM...(This Evening through Sunday)
ISSUED AT 325 PM CDT Sat Mar 25 2017

Immediate concern centers on the convective trends late this
afternoon and evening as a persistent clearing the in cloud cover
along and southeast of the stationary front was enhancing
destabilization. Overnight into Sunday, consensus has the surface
low tracking northeast through extreme southeast Iowa, leading to
an extended period of low clouds, fog and patchy light rain or
drizzle, once the convective potential ends this evening.

A brief window of possible strong to severe storms is shaping up for
far northeast MO into mainly our IL counties south of the I-80
corridor for roughly 4 pm to 7 pm. Building marginal MUCAPE, and low
level shear may lead to low top mini-supercells capable of hail and
an isolated tornado, if all were to come together just right. At
this time, most models have the better parameters just south of the
forecast area, where SPC has a marginal threat in the day one
outlook. Will keep at least isolated thunder in the forecast
across the south through mid evening.

Overnight, widespread fog and patchy drizzle/light rain will likely
follow in the low level deformation zone north of the slow moving
low. Have not included dense fog, but this will need to be monitored
overnight into at least mid Sunday morning as a weak low level
convergent wind field hangs back over the area. Temperatures will
remain nearly steady in this airmass until winds become more
northwesterly behind the departing low Sunday, and drier air moves
in. This should lead to Sunday afternoon temperatures in the 50s
to possibly lower 60s. Chances for light precipitation will be
higher in the morning, with any lingering rain ending from west to
east in the afternoon.

.LONG TERM...(Sunday Night through Saturday)
ISSUED AT 325 PM CDT Sat Mar 25 2017

...Active weather pattern continues this week...

Monday night and Monday, 12Z Saturday deterministic model runs show
skies will be cloudy but mainly dry on Monday night as the system
that brought rain over the weekend moves east into the Ohio valley.
The next 500 mb shortwave will approach the region on Monday, with
short range models progging this system to move to our south over
southern Missouri. This low track would bring a chance of rain
south of Interstate 80, with dry skies to the north. High
temperatures on Monday will be in the mid 50s across the north, to
near 60 over the south. Overnight low temperatures will be in the
40s.

Tuesday and Wednesday, These may be the only dry days during the
upcoming week as an upper level shortwave ridge and surface high
pressure build into the upper midwest. The next shortwave, located
over the desert soutwest, will begin to move northeast toward the
upper Mississippi valley during the day. High temperatures will once
again be in the mid 50s across the north, to near 60 over the south.
Overnight low temperatures will be in the upper 30s, north, and low
40s south.

Wednesday night through Friday, Forecast confidence is low as the
12Z Saturday model runs develop large descrepancies in their
solutions. The ECMWF brings a 500 mb closed low over the forecast
area and into the Great Lakes by 18Z Friday, while the GFS moves the
same low well to the south from Texas eastward to the lower Ohio
valley. The ECMWF solution would bring rain to the entire forecast
area, while the GFS solution would keep the rain well to our south.
High temperatures will be in the mid 50s north, to near 60 south,
with overnight low temperatures in the 40s.

Next Weekend, Forecast confidence remains low as large model
descrepancies continue. The ECMWF solution would once again produce
rain over the area, while the GFS remains dry. Kuhl

&&

.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...Sheets
SHORT TERM...Sheets
LONG TERM...Kuhl
AVIATION...RP Kinney



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