Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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739
FXUS63 KDVN 222311
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
611 PM CDT Mon May 22 2017

.UPDATE...
Issued at 605 PM CDT Mon May 22 2017

A sizable short term update was issued at 430 pm, in increase pops
north and south, but greatly reduce pops in the central areas.
This trend should continue into tonight, with mainly dry
conditions along central areas and any convection likely remaining
north and south of the CWA after 7 PM.

&&

.SYNOPSIS...
Issued at 250 PM CDT Mon May 22 2017

Lots of clouds and cool conditions at 2 PM CDT across the forecast
area with temperatures mostly in the mid to upper 60s with some
low 70s which is 5 to 10 degrees below normal for late May. Some
light showers caused by a broad area of upper low pressure system
which will stay in place over the region for at least the next 24
hours for more cool and wet conditions. Skies will begin to clear
by late Wednesday with still below normal conditions.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 250 PM CDT Mon May 22 2017

Short term forecast confidence assessment...average or fair with
main issue the coverage and intensity of light precipitation the
next 24 hours with upper low parked over the region. This may impact
highs by 3 plus degrees and low risk of localized rain amounts over
a quarter inch not out of the question of mostly showers and maybe
an isolated storm.

Tonight...Skies to be generally mostly cloudy to cloudy with possibly
areas of light rain and rainshowers developing toward daybreak and
maybe some areas of fog for later shifts to assess. Mins should be
near 50F far NW to the mid 50s SE sections. Most locations should receive
rain amounts well below a quarter of inch.

Tuesday...Continued cloudy and good chance of rain and maybe an isolated
storm with upper low pressure nearby. Areas of light fog may last until
the late morning with rain totals mostly light with some rain totals
over a quarter of an inch mainly east of the Mississippi River. Highs
depending on rain coverage mostly in the mid to upper 60s which will
be 10 plus degrees below normal most areas.

.LONG TERM...(Tuesday Night through Monday)
ISSUED AT 250 PM CDT Mon May 22 2017

There is a persistent signal indicating temperatures at or below
normal and unsettled weather conditions through the end of the month.

Tuesday night and Wednesday the upper level low will slowly move
through the area producing showers and possibly some thunderstorms.
Rainfall should be light but could approach one half inch in
thunderstorms.

Wednesday night the upper level low moves into the Ohio Valley. Rain
will end from west to east during the evening with dry conditions
after midnight.

Quiet and dry conditions will be seen across the area on Thursday as
high pressure moves through the Midwest. Temperatures will average
slightly below normal.

Thursday night on...

Thursday night a weak upper level disturbance will move through the
area. Moisture is limited and there are questions regarding the
overall depth of the dry air. The model consensus has slight chance
pops across most of the area after midnight.

Friday and Friday evening the next storm system will move through
the Midwest. There are differences between the models regarding the
timing and track of this system. The CMC global is more aggressive
in generating precipitation than the GFS. The ECMWF is further south
and keeps the area dry until late Friday night.

Right now the model consensus has chance to likely pops Friday with
the higher pops south of I-80. Friday evening the model consensus
has slight chance to chance pops east of the Mississippi and then
dry conditions after midnight.

Saturday through Monday the model solutions diverge even further.
There is a very loose agreement on an upper level low slowly
rotating across the area but there are disagreements on its
strength, track, and overall timing. Additionally, each model has
several smaller disturbances in the flow rotating around the upper
low of varying strength.

As a result, the model consensus has dry conditions Saturday
morning, then slight chance to chance pops Saturday afternoon/night.
Sunday through Monday the model consensus has slight chance to
chance pops for each day.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
ISSUED AT 1222 PM CDT Mon May 22 2017

VFR conditions will continue this evening, with mid clouds
remaining over the area. The showers should remain north of DBQ
and highway 20 after 00z, and should also remain south of BRL or
Highway 34 in the south. This mainly dry overnight will give way
to possible MVFR conditions Monday morning, but looking at the
conditions upstream, models are greatly over doing the low level
saturation, and there are mainly VFR conditions associated with
the upper low in western Iowa/eastern NE/SD that will impact this
area tomorrow. Thus, we have lowered the extensive MVFR forecast
of low cigs and visibility to show mainly VFR conditions, though I
left a scattered low cloud to show the possibility exists.

&&

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

$$

UPDATE...Ervin
SYNOPSIS...Nichols
SHORT TERM...Nichols
LONG TERM...08
AVIATION...Nichols



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