Area Forecast Discussion
Issued by NWS Quad Cities, IA IL
FXUS63 KDVN 261603
Area Forecast Discussion
National Weather Service Quad Cities IA IL
1103 AM CDT Wed Oct 26 2016
Issued at 1102 AM CDT Wed Oct 26 2016
MCS that brought 1 to 2 inches of rain to locations along and
north of Interstate 80 was diminishing rapidly east of the MS
River. The best 3hr pres falls were located in extreme northeast
IL with low level transport winds veering west over the cwa. The
axis of highest Pwat`s extended from OK to northeast IL.
The surface low pressure was analyized just east of Grinnell IA
and will track roughly along I-80 this afternoon, and be east of
the cwa by late afternoon. South of the low, temperatures will
warm into the 60s, while to the north readings will struggle to
reach 50. I will maintain a chance of showers and isolated
thunderstorms ahead of the surface low. Any lingering rain will
end in our far east by early this evening as the low pushes east
of the area.
Issued at 339 AM CDT Wed Oct 26 2016
A good portion of the cwa currently is dry as the area is
in-between forcing mechanisms, with last evenings warm advection
band of showers and storms having stratified while lifting into WI
and northeast IL. However, a band of showers and storms is quickly
moving back into northeast and east central IA early this morning
aided by strong and veering low level jet and rich moisture
advection (PWATs surging to over 1.25 inches), and diffluent flow
ahead of approaching mid level wave.
.SHORT TERM...(Today and Tonight)
ISSUED AT 339 AM CDT Wed Oct 26 2016
Surface low over west central IA early this morning on track
to pass near the U.S. Highway 20 to Highway 30 corridors today
then into northern IN this evening. Expect a transitory band of
showers and some storms from west to east through mid morning.
Shear is tremendous with 0-6km 40-50+ kts per SPC MESO page but
surface base CAPE is nil, with soundings depicting skinny CAPE
profiles above near surface stable layer. Given magnitude of shear
and skinny elevated CAPE can`t rule out some small hail and gusty
winds accompanying the stronger storms. Also, expect a period of
moderate to locally heavy downpours with the convection with PWATs
surging to near 1.25 inches. Speed of movement of linear band of
convection should limit amounts to 0.25 to 0.75 inch on average.
Expect the precipitation to generally diminish from west to east
by late morning through afternoon, transitioning to light rain and
drizzle perhaps for a while before ending. Areas along and east of
the Mississippi River could see redevelopment of scattered showers
and possibly an isolated storm this afternoon ahead of the low and
cold front/low level convergent boundary. Highs today are expected
to top out in the 60s much of the area south of the low track, or
roughly near to south of Highway 30. If any breaks in the clouds
it`s possible a site could touch 70 degrees over northeast MO and
far southeast IA. Expect the biggest temp gradient and
consequently most challenging high temp forecast from Highway 30
northward through Highway 20 where readings likely to drop off
through the 50s and possibly into the 40s very far north.
Tonight, any lingering light showers or rain should quickly exit
far eastern sections early in the evening. Cooler cyclonic flow
coupled with moist low levels should promote stratus lingering
through most if not all of tonight, with any partial clearing
most favored across the southwest cwa should it occur. Due to the
anticipation of cloudy to mostly cloudy skies I have opted to
keep lows on warm side of guidance blend or just above, with
readings generally in the lower to middle 40s.
.LONG TERM...(Thursday through Tuesday)
ISSUED AT 339 AM CDT Wed Oct 26 2016
Thursday: 1025mb sfc high over the Upper Mississippi River Valley
will bring dry weather and light winds. Temps will be slightly below
normal. Forecast highs range from near 50 F north to lower 60s SW.
Moisture trapped close to 925mb underneath a strong inversion is
forecast to gradually move out of the CWA from SW to NE through the
day. Low stratus will be last to clear or partially break up in the
NE which may take until the evening. Overnight lows are forecast in
Friday: Low pressure tracking along the U.S./Canadian border will
drag a +16 C 850mb thermal ridge through the Upper Mississippi
Valley. Breezy SW sfc winds gusting 25-30 mph (isolated near 40 mph)
and daytime mixing to result in optimal warming, allowing temps to
reach the lower 70s north and upper 70s SW.
Saturday: A cold front is forecast to sink southward through the
CWA during the morning and afternoon. 850mb temps are progged to
fall below 12 C across the north half of the CWA during the
afternoon. Thus, thinking the north to south max temp gradient is
going to be at least 10-15 F degrees. Have mid 60s north to mid
70s south at this time which could change slightly, especially
along north of I-80.
Precipitation: Collaborated with surrounding WFOs to include slight
chance POPs. Model consensus was dry. The latest ECMWF brings a
low-level frontogenetic band through the area during the evening
and overnight period. Will have to monitor for better model
agreement as discrepancies among the 00Z/10.26 models is large.
Forecast message right now...there is a chance for showers but
confidence remains low regarding areal coverage/intensity.
Sunday through Tuesday: Although weak upper disturbances may work
through the WNW mid-level flow, ridging will dominate the pattern
translating to above normal temperatures and mainly dry weather. The
coolest day is likely going to be Sunday when highs are forecast
closer to seasonal normals. The mid-level ridge then amplifies into
early next week in response to a digging trough in the Western U.S.
Both the GFS/ECMWF have 1000-500mb thicknesses eclipsing 570 dam by
early in the week. Forecast highs on Monday are again in the 70s
for most locations.
Wednesday: Low confidence in placement of a warm front and chances
for showers and thunderstorms. Mid-level flow turns southwesterly,
advecting moisture northward. The pattern may become active by
the middle of next week into the weekend. Uttech
.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
ISSUED AT 651 AM CDT Wed Oct 26 2016
Overall, conditions expected to level off i
Showers and a few storms with IFR to MVFR conditions will
gradually diminish from west to east through early afternoon. In
the wake, low pressure will move across the area this afternoon
accompanied by variable winds and pockets of very light rain and
drizzle. As it passes, winds will shift to the northwest and may
gust for a while at 10-20 kts. Considerable low clouds will wrap
in behind the low and expected to remain at the terminals through
tonight with generally MVFR to some IFR conditions and northwest