Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

FXUS63 KDVN 241141

Area Forecast Discussion
National Weather Service Quad Cities IA IL
641 AM CDT Mon Oct 24 2016


Issued at 345 AM CDT Mon Oct 24 2016

Dry, cool high pressure was centered over North Dakota early this
morning with ridge axis extending through the Missouri River
Valley. Our region is on the front flank of the high in lingering
cyclonic flow. Attendant to that is some stratus advancing
southward through Wisconsin. Otherwise, for the time being skies
are clear with seasonable temperatures ranging from isolated upper
30s to mid 40s.


.SHORT TERM...(Today and Tonight)
ISSUED AT 345 AM CDT Mon Oct 24 2016

High pressure will be the dominant weather feature providing dry
and cooler conditions with temperatures slipping back closer to
seasonal norms. The one potential fly in the ointment today, or
at least for this morning, is the area of stratus advancing
southward through Wisconsin. This is not being handled well by
models, which lends to lower confidence on sky trends today.
ACARS sounding data over southern Wisconsin shows an inversion
trapping clouds. The flow within the cloud bearing layer is
northerly around 20 kts, which is sufficient for propagation into
the cwa. However, increasing subsidence with the building high
may chew away or erode the clouds as they approach, and looping
11-3.9 micron satellite image seems to show some constriction to
areal coverage. The forecast will acknowledge some cloud potential
this morning especially north/east, but on a transitory basis with
a return to sunshine this afternoon. Confidence is low and will
continue to assess trends and update if needed. Otherwise, outside
of the potential period of clouds north/east this morning expect
mostly sunny skies with near normal highs mainly in the upper 50s
to lower 60s. Winds much lighter and trending northeasterly by
afternoon around 10 mph.

Tonight, the high pressure ridge will slide toward the Ohio Valley
with winds becoming light easterly. The one challenge is lows, as
there will be a battle between dry ground and light winds, and
increasing high level cloudiness spilling down lee of Plains upper
ridge axis. Have shaved a couple degrees off lows near and east
of the Mississippi River where likely to stay mainly clear longer
and have drainage areas of Sauk and Rock River Valleys down in
the mid 30s with patchy frost. Elsewhere, expect upper 30s to lower

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 345 AM CDT Mon Oct 24 2016

Tuesday into Wednesday Morning: Approaching shortwave trough
emerging from the Central Rockies into Nebraska and South Dakota
will flatten the ridge over the Midwest. Elongated 850mb low will
eventually form along the lower tropospheric baroclinic zone,
lifting an elevated warm front northward through E Iowa/NW
Illinois into Minnesota and Wisconsin into Tuesday night.

Moderate to Heavy Rain placement: The low-level warm air advection
and frontogenesis, which specifically stands out at 850mb, is
forecast by the models to rapidly increase in magnitude through
this period. Since upper kinematics are weak, so too are the
dynamics and ageostrophic winds. Consequently this precip event
will primarily be driven by thermal advection and frontogenetical
circulations along the elevated warm front. The most favored
location for the heaviest band of rain is across NE Iowa/SE
Minnesota/into Wisconsin where 1-2 inch rain totals are possible.
Further south in the DVN forecast area, forcing for ascent is
lower. Best chances for rain may hold off until late Tuesday
night through Wednesday morning along the low-level cold
front/convergent boundary.

Forecast Anomalies: NAEFS PWAT anomalies are forecast above the
90th percentile for late October (1.25 inches). The aforementioned
strong thermal forcing coupled with the anomalously moist
atmosphere increases confidence in the occurrence of a moderate to
heavy band of rain along a west to east axis, most likely focused
north of our area.

Model Differences: The ECMWF is furthest south hitting at least
the NW third of the CWA with the steadier frontogenesis precip.
Thus, still time for the model consensus to shift placement of the
moderate to heavy band. But as it stands now, it is more likely to
be north of the local area.

Thunder Potential: Both ECMWF/GFS have a plume of MUCAPE
along/ahead of the cold front, enough to mention thunder chances.
Appears the greatest risk for storms is across the SW half of the
forecast area with MUCAPE possibly exceeding 500 J/kg. Low shear
precludes a severe threat at this time.

Wednesday Afternoon and Thursday: Lingering showers with possible
embedded/isolated storms Wednesday afternoon, mainly along and east
of the Mississippi River will diminish by the evening as the low
pulls away. After morning lows in the 40s, temps are forecast to
rebound to seasonal levels into the upper 50s to lower 60s
Thursday afternoon.

Friday: Next clipper system slides through the Great Lakes. Brunt of
forcing/mid-level height falls stay well N/NE, only warranting 20-
30% POPs for now. Otherwise, above average temps are forecast -
mid/upper 60s most locations with lower 70s in the south.

Saturday through Monday: Although weak upper disturbances may work
through the WNW mid-level flow, ridging will dominate the pattern.
This translates to slightly above normal temperatures and mainly
dry weather. Uttech


.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
ISSUED AT 633 AM CDT Mon Oct 24 2016

Stratus with high mvfr ceilings sagging southward through Wisconsin
and far northeast Iowa continues to erode. Incoming subsidence
and large dry wedge above cloud bearing layer should support
continued erosion thus I have maintained vfr conditions at the
terminals, with a mention of scattered cu with mvfr bases this
morning at DBQ and just some cirrus at all sites the rest of the
forecast period. Northerly winds around 10 kts will turn light
easterly by tonight.




LONG TERM...Uttech
AVIATION...McClure is the U.S. government's official web portal to all federal, state and local government web resources and services.