Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 272038
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
338 PM CDT Mon Mar 27 2017

.SYNOPSIS...
Issued at 330 PM CDT Mon Mar 27 2017

MSAS surface pressure fields showed a weak surface trough over the
area reaching northward from a low over far SE MO. The northern edge
of the main precipitation shield associated with this surface low
and upper level low tracking through southern MO was southeast of a
line from Mount Pleasant IA to Princeton IL. A separate elevated
narrow band was over the Quad Cities to Sterling IL. Extensive
stratus continued to cover the forecast area, which combined with
light winds and abundant low level moisture, was resulting in mid
afternoon temperatures only in the upper 40s to lower 50s.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 330 PM CDT Mon Mar 27 2017

Persistence will again be the rule as weak synoptic features and a
deep layer of low level moisture prevails overnight through much of
Tuesday. This will keep the low level stratus in place, while light
surface winds and moist low level conditions may lead to more
overnight and early morning fog.

At the surface, the low moving through the mid Mississippi Valley
quickly exits eastward with the progressive strong upper level wave
shortwave embedded in the zonal flow aloft. This is followed by weak
ridging at the surface and aloft advancing through the local area
overnight into Tuesday. The resulting light north to northeast low
level flow will channel a deep low level moist airmass, as evident
by 12z soundings at DVN, MPX and GRB, over the area. Considering the
developing weak advection of slightly lower surface dewpoints from
the north and northeast overnight, have gone with slightly lower
mins than last night, but warmer than most most guidance, ranging
from the upper 30s northeast to lower 40s south. The weakly
convergent lingering cyclonic flow will be favorable for at least
patchy light fog. Overall, the setup is less favorable than the past
couple nights, but will still include patchy fog wording.

Tuesday, the big question will be how far south the northern edge of
the stratus can advance southward, and amount of thinning elsewhere
as surface and upper level ridging provide a period of weak
subsidence. For now, will lean on the pessimistic side and keep
mostly cloudy wording, which would limit highs to the mid and upper
50s.

.LONG TERM...(Tuesday Night through next Monday)
ISSUED AT 330 PM CDT Mon Mar 27 2017

Tuesday night and Wednesday...12z run models suggest enough sfc and
upper ridging to hang on acrs the region ahead of the next southern
stream cyclone organizing acrs the southern plains, for a mainly dry
night to start the period off with. Mid to high clouds to thicken
from the west as the night progresses, and maybe just some light
overrunning rain/sprinkles in the southwest toward dawn. Cool lows
in the mid 30s in the northeast, to the lower 40s in the south. Then
partially blocked closed low to slow roll acrs eastern OK and SW Mo
bi midnight Wed night. Precursor brisk easterlies in the llvls to
act as drying precip inhibitor on Wed especially east of the MS RVR,
but strengthening SSW LLJ of 30-45 KTS and seasonably high PWAT feed
of 0.80 to over an inch will saturate the column and look to fuel a
moderate to locally heavy elevated precip event Wednesday night
through Thu morning. Leeside synoptic scale lift off northern stream
upper trof and eastern plains/MO RVR Valley cyclone squeezing out
the available moisture could lead to rainfall amounts of Three
quarters of an inch, to well over an inch acrs the area by Thu
afternoon. If the rainfall is widespread enough, could see some
within bank rises on area rivers and streams. Initial LLVL jet surge
and mid layer 150+ J/KG MUCAPEs may produce some embedded thunder in
the southern CWA Wed night, and may have to move up timing to the
evening and spread further north in subsequent fcst packages.

Thursday into Friday...After the morning showers and some thunder
linger for portions of the day Thu, more optimum LLJ feed and lift
off passing northern stream trof shift off to the east of the local
FCST area late in the day and overnight. But some lingering TROWAL
circulation feed to keep areas of rain/showers going acrs the
southeastern half into Thu evening, before the precip tapers off to
light rain/sprinkles/drizzle overnight. Would appear another fog
window on hand for Thu night, but models suggest enough llvl
pressure gradient on the departing low`s northwest flank to make for
brisk northeast sfc winds of 10-20 MPH Thu night which may mix out
at least dense fog potential. Also the models suggest enough llvl
cooling to make for a rain-snow mix in the far north later thu night
into early Fri morning if precip lingering in those areas long
enough. But the cooling is in the sub-H85 MB inversion layer and not
confident the cool depth enough for a mix and it probably will stay
all cold light rain or drizzle. Wrap around clouds and possibly some
occasional sprinkles to make for not a very nice Fri in the wake of
the system...highs upper 40s to low 50s.

Saturday through next Monday...Latest run medium range models
suggest a temporary lull in the cyclone parade for Sat. Hopefully at
least some partial sunshine will help relative cool air mass in
place to recover for highs around normal for early April or even a
few degrees above normal on Sat. Then the medium range solutions
diverge in handling the next looming southwestern plains cyclone,
the ECMWF lifts it out for another wet period late Sat night into
Sunday, while the 12z GFS and it`s stronger upper ridge lobe holds
it at bay until later on Monday. For now will let the blend go which
allows a initial piece of the upper low to eject out for overrunning
rain chances late Sat night into Sunday morning, then a lull later
Sunday into Sunday night before rain chances increase again from the
south on Monday as the main upper circulation center rolls out along
and just to the northwest of the mouth of the OH RVR Valley. Low
confidence in this and see a slowed scenario unfolding, keeping Sat
night into Sunday morning dry, with the main system lifting out late
Sunday and lingering rain chances into midday next Monday. ..12..

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday Afternoon)
ISSUED AT 1242 PM CDT Mon Mar 27 2017

Low clouds will persist through the forecast period as a weak area
of low pressure moves across Missouri into southern Illinois.
Associated light rain and drizzle will affect only the BRL site
this afternoon, where there is a potential for periods of IFR
conditions. Most of the area and other TAF sites will have MVFR
conditions due to low ceilings this afternoon. Overnight,
confidence is high that there will be a return of widespread
IFR conditions as ceilings lower and fog develops. A window of IFR
conditions has been included at CID and DBQ. A gradual, low
confidence improvement to MVFR is expected Tuesday morning.

&&

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

$$

SYNOPSIS...Sheets
SHORT TERM...Sheets
LONG TERM...12
AVIATION...Sheets



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