Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 161201
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
701 AM CDT Thu Mar 16 2017

...12z AVIATION UPDATE...

.SYNOPSIS...
Issued at 342 AM CDT Thu Mar 16 2017

Surface ridge axis extends from western WI through central IL
early this AM. Near calm winds and clear skies leading to
excellent radiational cooling setup, which has allowed
temps to plunge into the single digits to near 10 degrees
over portions of the northeast IA over the deeper snow cover.
Elsewhere, temps were in the teens to lower 20s. Satellite
and obs show a band of lower clouds working into eastern IA and
northeast MO within a zone of warm advection on backside of the
departing high pressure ridge.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 342 AM CDT Thu Mar 16 2017

Forecast focus is with precipitation chances later today and
especially tonight.

Surface high pressure ridge from western WI through central IL
will continue to shift east today. Lower clouds will then
progress eastward into the cwa this AM within the return flow/
warm advection processes, and may eventually erode or diminish
with WAA weakening and presence of drier e/se fetch from
departing high. Then likely to see mid/high clouds overspread
the area this afternoon with renewed surge of deep layer WAA
ahead of an approaching shortwave. Overall, expecting skies
partly to mostly cloudy today with a sunny start in many areas
east of the Mississippi River. Developing this afternoon will
likely be some elevated returns initially within WAA with low
levels still parched. However, by late this afternoon and
especially this evening saturation of the low levels is likely
aided by frontogenesis ahead of an approaching shortwave.
Near freezing wet bulb temps and initial dry air may lead to some
snow or rain/snow mix... with areas DBQ-SQI northeast more
favored for any snow initially while rain favored southwest of
this corridor within surging warm nose aloft and saturation. Temps
at worst may be right at freezing or just above during this
precipitation over the northeast CWA, thus not expecting
significant impacts. Having said that, taking a sneak a peek at
the 06z NAM and it has markedly ramped up the lift within the DGZ
this evening over the corridor from near DBQ to SQI to FEP, and
consequently has trended much wetter (just over 0.2 inch). This
would necessitate higher pops and qpf for our northwest IL
counties especially, but being an outlier did not make any last
minute adjustments and staying with consensus of a light qpf event
up to near 0.1 inch. The stronger lift on the NAM would spell
quicker saturation, thus mostly rain. Key would remain with the
boundary layer temps which are still shown to be at or just above
freezing thus still likely limited if any impacts... but will need
to be watched.

Eventually by mid evening tonight the initial WAA band will
likely be exiting our northwest IL counties. Later in the evening
and overnight some weak lift is progged back across the area with
diffluent flow aloft ahead of shortwave. Forecast soundings
generally show loss of ice aloft with drying and moisture trapped
beneath inversion, thus may be more of a drizzle on precip type or
patchy light rain at times if deeper moisture coincident with
lift.

Highs today challenging between cloud trends and snow cover.
Low level thickness and verification of highs yesterday and
factoring in snowmelt should allow areas of the better snow cover
north of I-80 over eastern IA to reach above freezing with
widespread 30s. Immediately south of the snow cover expecting
40s with then some lower 50s far northeast MO.

Temps tonight not expected to fall much with continued low level
WAA and moistening, and in fact may see most areas steady to
rising several degrees.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 342 AM CDT Thu Mar 16 2017

Friday through Sunday:

Highs are forecast closer to mid March normals for Friday and
Sunday, but a little cooler on Saturday.

NW wind gusts of 20-30 mph are expected Friday afternoon, highest
over the W/NW section of the CWA. However, temps will be mild into
the 50s with low 60s far south.  On Saturday, a cold punch of 0 C to
-4 C 850mb air into the early afternoon, and persistent NW sfc
winds, will hold temps slightly below normal. Forecast highs range
from the low 40s far north to low 50s far south.

Sunday Night:

850mb moisture transport vectors align from the southern Plains into
the Midwest. ECMWF/GFS quickly increase elevated instability as
lapse rates steepen above 700mb and 850mb mixing ratios reach
10 g/kg.

Added slight chance for thunder - which may need to be increased in
future updates if models continue to show MUCAPE at or above 1000
J/kg and +40 kts of 0-6 km bulk shear. PoPs at this time are 30-50%
and confidence on areal coverage is low.

Monday:

Models differ on location of cold front associated with area of low
pressure over NE Ontario and the Hudson Bay region. Have shower
chances through the afternoon. Any precip that occurs should be
light.

Tuesday through Wednesday Afternoon:

Dry period with high pressure sliding into the Upper Midwest.
Forecast highs are near to slightly below normal in the lower to
upper 40s most areas in the CWA.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday Morning)
ISSUED AT 653 AM CDT Thu Mar 16 2017

Vfr conditions expected today with cigs generally 4-10kft agl.
A band of warm advection light snow or rain is possible this
afternoon into early evening. Tonight, increasing low level
moisture in combination with snowmelt will likely result in
lowering cigs into MVFR range, with patchy fog. In addition
an upper level disturbance will aid the development of some
light rain or drizzle, with a low chance of IFR conditions.

&&

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

$$

SYNOPSIS...McClure
SHORT TERM...McClure
LONG TERM...Uttech
AVIATION...McClure



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