Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 240941
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
341 AM CST Fri Nov 24 2017

.SYNOPSIS...
Issued at 250 AM CST Fri Nov 24 2017

Satellite shows some high level WAA induced cloudiness shifting
across the region early this AM, most prevalent across southern
IA. Temperatures varied quite a bit across the area early this AM.
At the surface, a weak ridge axis was positioned over northwest
IL. Near calm winds and mainly clear skies was leading to ideal
radiational cooling setup, and resulting in temperatures in the
upper 20s to lower 30s in some low-lying areas. Meanwhile, across
portions of eastern IA the pressure gradient was increasing
between this surface ridge and low pressure over western Ontario.
This is leading to a strengthening southerly wind to around 10+
kts in some areas and consequently not as cold temperatures in the
upper 30s to lower 40s. A cold front attendant to the Ontario low
will pass through the region tonight. A marked and potential
record breaking warm-up is on tap today on gusty S/SW winds ahead
of the front, and will be followed by a return of cooler conditions
tonight.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 250 AM CST Fri Nov 24 2017

Early AM high cloudiness will thin leading to a mainly sunny sky
for much, if not all of today. This abundant solar insolation
will aid good boundary layer mixing, and coupled with an increasing
pressure gradient will lead to breezy/windy conditions with SSW
winds 15-30+ mph. These winds will also fuel a marked warm-up today
with most of the area topping out in the 60s, as 925 mb thermal
ridge (10C-15C) arrival coincident with deeper mixing and timing of
peak heating. This past Monday we saw many areas of eastern IA and
northeast MO top out in the upper 50s to lower 60s, with 925 mb temps
of around 9C. As mentioned, 925 mb temps today are progged in the
range of 10C-15C. Mixing down these warmer temps from near 900 mb as
supported by BUFR soundings actually yields widespread highs in the
upper 60s to lower 70s! However, considering late November lower sun
angle /weaker solar insolation/ and potential for some increase in
high cloudiness returning this afternoon attendant to right entrance
region of Great Lakes jet streak, tempered this mixing potential.
Even still, I`m thinking widespread 60s and likelihood of some record
highs being reached or exceeded. Please refer to the climate section
below for information on record highs today at the main climate sites.
The gusty SSW winds and unseasonably warm temperatures will also
contribute to a very high fire danger this afternoon, and any outdoor
burning will be strongly discouraged.

The cold front is expected to sweep through the area this evening, with
little fanfare aside from some mid/high cloudiness and a wind shift to
the NW which may be gusty at times for a while after frontal passage.
Models do show a mid level frontogenetical band passing quickly
through late afternoon and early evening, especially just to our north
where additional enhanced forcing from favored lift quadrant of upper
jet could have just enough atmospheric moisture to squeeze out some
sprinkles. Concerns with plenty of dry sub-cloud air and high cloud
bases after top down saturation to between 600-700 mb aided by deepening
NW flow beneath. But, this is just a few drops at worst case for a short
time that would be most favored post-frontal north of I-80 toward 00z
and just beyond. After that, then decreasing clouds and a return to
cooler and more seasonal conditions, with lows mostly in the 30s to near
40 degrees.


.LONG TERM...(Saturday through Thursday)
ISSUED AT 250 AM CST Fri Nov 24 2017

Saturday and Sunday...Saturday looks to be a post-frontal and rather
blustery day, prefer the 00z GFS deeper mixed winds in incoming
ridge pressure gradient driving northwest winds of at least 12-18
MPH sustained with higher gusts. Despite cool air advection, mixing
winds in dry environment to help high temps make it into the upper
40s to mid 50s acrs much of the local fcst area Sat afternoon. Clear
skies and light sfc winds under passing sfc ridge axis with ongoing
dry sfc layer will make for a chilly night Sat night with many areas
dipping at least into the upper 20s. While upper ridge maintains
acrs the Rockies, lee side northwest flow will spill down a clipper
system into the northern GRT LKS by Sunday evening. The local area
will be the beneficiary in this systems warm draw/return flow on
Sunday with widespread highs in the 50s, some areas in the south
possibly pushing the upper 50s making for a large diurnal swing from
chilly Sat night temps. Then a dry weak FROPA lat in the day Sunday.

Monday and Tuesday...Most of the 00z run medium range models suggest
active eastern Pacific wave energy to pummel it`s way inland early
next week, with the upstream ridge getting pressed eastward toward
the MS RVR Valley by late Monday. The CWA will look to become bathed
in full blown breezy southerly return flow Monday, with early
indicated warm advection values suggesting highs in the upper 50s
and even some 60s possible, especially if the milder GFS has it`s
way. The medium range models then suggest almost a split flow
pattern developing acrs the mid CONUS, with lead vigorous wave acrs
Canada outpacing it`s southwestern U.S. counterpart to the eastern
James Bay region by late Tue. The sfc frontal system off this
northern passing low will look to sag through the area by early Tue.
Weak to marginal moisture advection and convergence along this
boundary as it pushes into a dry airmass, but the 00z run GFS does
break out some light rain along it on Tue, while the 00z ECMWF has a
dry FROPA thru the local area. For now will keep the blend`s slight
CHC POPs in the east, and watch later model run trends.

Wednesday and next Thursday...As long as the Canadian system and the
southwestern CONUS low stay unphased, the southwest low will look to
be a straggler and roll acrs the mid CONUS sometime mid next week,
with Wed looking to be the main window. There area medium range model
differences on how far north or south this system will track, with
the new ECMWF farther north and rolls the low acrs the southern half
of the DVN CWA. The Euro`s further north track also makes it milder
and suggests mainly a light to moderate rain event Wed into Wed
evening.

The 00z GFS propagates the main low acrs MO and southern IL, with
cooler thicknesses suggesting a possible rain-snow mix as it
saturates and enters the CWA Wed morning, and possibly as it exits
Wed night in top-down cooling on it`s northwestern flank. For now
will hi-light the mix potentail or even a switch to all wet snow from
north-to-south Wed night, but will have to watch additional model
runs for higher confidence in this system`s track and thermal
profiles...may take several days. Chances are that with even the GFS
solution, that more rain than snow or a mix will occur. This system
will look to exit by Thu, but longer range indications and upper
jet trends suggest that the next digging upper trof lurks just off
to the west. As it moves in overhead by Thu night, some chance it
will interact with the departing low/try to phase, but at this point
hard to say if any resultant precip would impact portions of the
local area like the 00z ECMWF suggests, or stay off well to the east
and north like the 00z GFS suggests.  This TROF will be colder core
though, and bring about a chill down for the end of the week but
right now does not appear like anything extreme.    ..12..

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1122 PM CST Thu Nov 23 2017

Southwest winds around 40 to 50 kts at roughly 1000 to 3000 ft agl,
above much lighter south winds at the surface are expected to develop
Friday morning. This will result in low level wind shear conditions,
which has been added to all sites between 11z and 16z. After 16z,
surface winds will increase and become gusty from the southwest at
15 to 25 kts through the afternoon, then decrease as a front moves
through toward evening. Otherwise, conditions will remain VFR with
only high level cloud cover.

&&

.CLIMATE...
ISSUED AT 250 AM CST Fri Nov 24 2017

Record Highs for November 24...

Moline.........66 in 1966
Cedar Rapids...63 in 1931
Dubuque........63 in 1931
Burlington.....68 in 1915

&&

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

$$

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



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