Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 220248

Area Forecast Discussion
National Weather Service Quad Cities IA IL
948 PM CDT Tue Mar 21 2017

Issued at 930 PM CDT Tue Mar 21 2017

Have updated to increase sky cover overnight and adjust mins up a
bit especially east central IA into northwest IL.

Lake Mi stratus propagating SSW at near 20 kts in wake of
pronounced wind shift. NAM and RAP mslp and surface wind fields
bring this lake enhanced boundary into far eastern cwa prior to
05z then toward Mississippi river overnight before washing out in
developing broad northeasterly low level flow. Attendant to this
boundary and evolving broad northeast flow at 20-25 kts in 1-3kft
agl layer will be lake enhanced stratus. NAM/RAP low level rh
progs have a decent handle on the lake stratus and followed for
sky grids going with pt-mocldy developing overnight across NW IL
into portions of eastern IA especially through the Hwy 30 to I-80
corridors... possibly reaching near IOW/CID toward daybreak. As a
result of this increase in cloud cover I have also nudged up lows
a bit. SW cwa will continue to see sct-bkn high cloudiness at
times overnight. Overall, expect skies to become partly to mostly
cloudy across much of the cwa. Updated grids/PFM/ZFP have been sent.


Issued at 307 PM CDT Tue Mar 21 2017

As expected the mid-level frontogenetic band of rain, triggered
by a short wave moving quickly across Iowa, has continued to
diminish and was pushing rather quickly to the southeast. The HRRR
model indicated the rain should exit the dvn cwa by late this
afternoon (4 pm).


.SHORT TERM...(This Evening through Wednesday)
ISSUED AT 307 PM CDT Tue Mar 21 2017

Forecast focus on dry but chilly weather in the short term.

Tonight: Subsidence in the wake of the short wave pushing off to
our east should bring clear to partly cloudy skies for most of the
night. Canadian high pressure (1040 mb)centered in Manitoba will
slide to Lake Superior by sunrise. This will funnel cold air into
the area on north to northeast winds. Minimum temperatures will
be in the 20s.

Wednesday: As the high pressure pushes towards the eastern Great
Lakes region, winds will veer to the east to southeast. Mid/high
level clouds should increase as gradually strengthening mid-level
warm air advection develops on the return flow. The thickening
cloud deck should keep temperatures on the chilly side for late
March, with highs in the lower to mid 40s. This would be about
10 degrees cooler than normal.

.LONG TERM...(Wednesday Night through Tuesday)
ISSUED AT 307 PM CDT Tue Mar 21 2017

The weather pattern will be turning very active the second half of
the week across the Midwest and is expected to continue through the
end of the month. Some of the extratropical cyclones that develop
across the CONUS will have the potential to be strong. Water vapor
imagery shows numerous storms across the Pacific Ocean all the way
into eastern Asia.

That being said, the active pattern does not mean there will be a
continuous rain. There will be periods of dry weather. However,
precipitation does have the potential to average above normal
through the end of the month.

Quiet and dry conditions will be seen across the area Wednesday
night as high pressure moves into the eastern Great Lakes. Attention
then turns to the first rain event for Thursday.

The strength of the high and depth of the dry air will dictate when
precipitation develops and what it will initially be on Thursday.
The current model consensus has slight chance to chance pops west of
a Galena to Kewanee, IL line Thursday morning. However, this will
likely be the areal coverage by the noon hour on Thursday. The
entire area may start out dry at sunrise Thursday.

Profiles of the atmosphere do show a layer of dry air at the
surface. This dry air may be just enough to allow an initial period
of sleet before quickly changing to a rain/snow mix and then all
rain as the dry layer saturates.

Thursday afternoon there should be an area of rain moving from south
to north across the area as the stronger forcing acts upon an
elevated front moving through the area.

Thursday night the better forcing and elevated front move north of
the area. The increasingly moist and unstable air should allow the
precipitation to be showers with some elevated thunderstorms north
of I-80.

Mainly dry conditions should be seen across the area Friday morning
while the next storm system moves out of the Plains. By Friday
afternoon scattered showers along with some thunderstorms are
expected to develop with the better coverage west of the
Mississippi. Temperatures look to be well above normal.

Friday night on...

While the weather pattern is projected to remain very active, the
models continue to vary considerably from run to run on the overall
track and details regarding each storm system.

Dprog/DT of the model runs is suggesting a southward shift in the
storm track Friday night into Saturday.

Friday night and Saturday the model consensus has likely to
categorical pops. While the models disagree on the overall track and
details, it is starting to look like a widespread general rain event
with some embedded thunderstorms. Temperatures should generally
average above normal.

Saturday night into Sunday the model consensus has chance to likely
pops with the next system moving through the Midwest. The model
solutions are diverging on their respective solutions regarding how
quickly the system will exit the area or where it will track. Right
now the precipitation type looks to be all rain. There may or may
not be some embedded thunderstorms.

Sunday night the model consensus has slight chance to chance pops
mainly west of an Independence, IA to Macomb, IL line for the next
storm system. Depending upon on how quickly this system arrives, the
possibility does exist that Sunday night could be dry.

The model consensus has chance to likely pops on Monday and chance
pops Monday night for the next in the sequence of storm systems
moving through the Midwest. Right now the precipitation type looks
to be rain.

On Tuesday, the model consensus has mainly dry conditions for the area.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
ISSUED AT 938 PM CDT Tue Mar 21 2017

Lake enhanced stratus is moving SSW at near 20 kts being handled well
by low level NAM/RAP rh progs, and supports MVFR cigs developing into
MLI overnight and possibly expanding to the other terminals as well.
Will update forecasts as trends play out in the next few hours. Northerly
winds around 10 kts will turn easterly overnight and may gust for a brief
period of time.




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