Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 191744 AAA

Area Forecast Discussion...UPDATED
National Weather Service Quad Cities IA IL
1244 PM CDT Sat May 19 2018

Issued at 1242 PM CDT Sat May 19 2018

Difficult short term forecast for sure today. With weak synoptic
flow and forcing, a purely mesoscale forecast prevails. Surface
fields are a mess and until more heating can occur will likely
stay that way. CAMs are all over the place with solutions as the
HRRR continues to catch up to current forecasts. The NAMnest, is
the most aggressive model as far as storms go this afternoon and
evening. Overall this will be a watch the MCVs and other
mesoscale features this afternoon into the evening. Currently, one
MCV is located across S IA and has fired new convection that
should head N/NE. This could affect the NW CWA this afternoon.
For this evening, questions still remain with convection across NE
KS. If this can fire, nothing should stop it from growing upscale
and heading this way late. Today is not a day to follow the
latest HRRR, as things are changing fast.


Issued at 330 AM CDT Sat May 19 2018

The latest sfc analysis was indicating messy boundary pattern acrs
much of the mid to upper CONUS. But there appears to be two main
features with one acting as a cool front stretching from northwest
of LK Superior, down acrs northwestern IA and into the central
plains. Another continued to be a weak quasi-stationary boundary
laying out acrs northern MO. Aloft, active and rather wavy
southwesterlies extended from the southwestern CONUS, to the eastern
OH RVR Valley. The split flow, blocked pattern will look to extend
well into next week making for almost daily chances of some precip
in or near the local area through the period.


.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Sat May 19 2018

Today...will keep some patchy fog in the south and east through
sunrise, but extent of both lower and high level cloud cover may be
helping keep a lid on more widespread and dense fog development.
Then the rest of the day will vary from mostly cloudy, to a mix of
clouds and sunshine. Enough thinning of the clouds and llvl mixing
to help make for another warm day in the upper 70s to lower 80s
along with a light and variable sfc wind regime. Will keep the area
dry until the upstream cool front sags into the CWA from the west as
the afternoon progresses. The convective allowing models, as well as
a few of the regular solutions develop sctrd convection along the
front by mid afternoon, with the northwestern third or more from
Iowa City up to Dubuque on west the more prone spots to experience
this activity. The shear profiles are fcst to be weak with this
afternoon/early evening activity and buoyancy driven if marginal
cap gives way. Thus a low chance of severe unless a small localized
microburst occurs. Much will depend on ongoing convective systems
roiling acrs NE and KS ATTM and how the remnants affect the area,
but new MCS/convective spawning grounds look to come together by
this evening acrs eastern KS into southeast NEB/NW MO and far
southwest IA.

Tonight...The cool front will continue to sag east acrs the CWA,
switching the llvl flow post-frontally to the north and northeast
acrs much of the area as the night progresses. Besides for a few
lingering showers/storms around the FROPA process, the main precip
scenario will be storm clusters or even a type of MCS that has
developed from the upstream convective initiation zones, moving in
from the west. The first wing or cluster may move in acrs the
southwestern CWA by mid evening, with other storms or portion of na
MCS moving acrs much of the rest of the area overnight and into the
early Sunday morning hours. Some signs of a larger and stronger
system feeding east-southeast into more robust deep convective index
regions further south acrs MO...which may rob THTA-E feed to the
north into the local activity.

If the frontal passage can keep a stable sfc layer, the storms
moving acrs the area should be elevated limiting the threat to
hail. The exception may be for storms moving acrs the southern CWA
that may get more shallow rooted or close to the front itself and
possibly produce a damaging wind threat in increasing deep shear
profiles, but CAPEs are projected to wane after midnight in those
areas. Incoming storms will also have to battle lingering mid
level ridging over and just east of the local area. Thus agree
with SPC`s limit of slight risk of svr storms to the far south and
southwestern CWA. Some potential of locally heavy rainfall under
passing storm clusters, but with recent dry weather and vegetation
growing at full pace(besides immature crops), we should be able
to take a round of heavy rain(1+ inches) without much of a flood
threat.  ..12..

.LONG TERM...(Sunday through next Friday)
ISSUED AT 330 AM CDT Sat May 19 2018

Active weather regime continues through the extended.

Sunday into Monday: Well-timed upper wave crossing the area during
peak heating will support scattered showers Sunday, with increasing
coverage during the afternoon. Surface front laying out over
northern Missouri will provide a focus for storms in southern
portions of the service area as indicated by the SPC day 2 marginal
risk area. Initial round likely ongoing in the morning driven by
strong low level jet, and additional storms likely in the afternoon
with aforementioned upper wave. Precip chances linger into Monday
with ripples in the quasi-zonal flow aloft and only weak surface
ridging over the area.

Tuesday: Surface ridge builds into the area for what is shaping up
to be best chance for a dry day across the area.

Wednesday through Friday: Low level return flow and generally
northwest flow aloft will keep active pattern alive through the end
of the work week, with daily storm chances.


.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
ISSUED AT 1242 PM CDT Sat May 19 2018

Good flying conditions are expected through the rest of the day
(00z Sunday) with VFR conditions expected. After 00z chances for
thunder and MVFR conditions increase. Storms should be scattered
in nature and could be strong. Towards the morning tomorrow, most
TAF sites will be close if not IFR.




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