Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 191739
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1239 PM CDT Sun Mar 19 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 330 AM CDT Sun Mar 19 2017

SFC ridge overhead to move out allowing return flow warming today,
with focus then turning to a frontal system dropping out of the
northwestern High Plains and acrs the area tonight for thunderstorm
chances.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Sun Mar 19 2017

Today...SFC ridge currently perched acrs the mid and upper MS RVR
Valley, will push east allowing for increasing southeasterly return
flow today into this evening. Would be a decent warm up today, but
some concerns of rounds of mid and high level warm air advection
clouds filtering the insolation for portions of the day hampering
the warm up potential. But will take a gamble and lean toward the
milder high temps of the 00z ECMWF MOS which did better then the
american models during the last warm up day this past Friday. This
translates into low to mid 50s in the northeastern third of the CWA,
to the upper 50s to around 60 in the south/southwest. Will keep the
fcst dry through 00z, but sctrd showers and some thunder will
percolate and move acrs MO today and may get close to the southern
boundary of the CWA at times.

Tonight...Flattening upstream upper ridge into a westerly steering
flow acrs the upper Midwest, will usher acrs a vort max and shunt
a boundary acrs the CWA from the northwest in a NE-to-SW oriented
fashion by early Monday morning. Southwesterly LLJ of 35 to 40+
KTs still on track to advect a plume of elevated THTA-E air acrs
the region overnight, with mid level lapse rates pushing 7 C/KM
and MUCAPES in the layer of 800 J/KG in the northeast, to over
1500 in the south from 6z-12z Mon. FCST soundings suggest storms
to be rooted at H85 MB, and effective shear profiles through that
column at 30 to 40 KTS but look west-to-southwest uniform flow in
the storm layer. Thus more speed shear based. Freezing levels
expected to be from 10K to 11500 FT AGL, and the thermodynamics
combined with the shear support elevated thunderstorms capable of
producing hail, but overall size potentail looks lower as compared
to a few nights ago. But still, the current progs suggest hail
stones up to ping pong ball with the strongest storms, but more
likely in the way of 1 inch to 1.25 inch(half dollar).

The 00z run models vary on where the elevated convection will
develop/initiate tonight, with half suggesting north of I80 after
03z Mon, others not until after midnight and mainly along and south
of I80. Will hand modify a SREF POP blend from northwest-to-
southeast as the night progresses, with highest pops after midnight
in the east and southeast. MCS/convective forcing progs of the NAM
and UKMET suggest better support for stronger storms and more
widespread activity/elevated MCS type storm cluster taking off more
east and southeast of the DVN CWA acrs northeast IL into central IL
and into western Indiana late tonight into early Mon morning. But
again the local area looks to be an initiation ground. Will go with
lows in the 40-45 degree range for most of the CWA except milder in
the far south. Also, some fog possible toward dawn Mon morning in
lingering sfc convergent zone along the main front, or any rain
cooled outflow interaction...but will not put in those details for
now and let the showers/storms be the main focus for tonight.
   ..12..

.LONG TERM...(Monday through next Saturday)
ISSUED AT 330 AM CDT Sun Mar 19 2017

Unsettled late March weather, light to moderate rainfall episodes
later in the week.

Long Term Forecast Confidence Assessment...fair to poor or average
to below average,  challenges are any light precipitation Tuesday
and evolution of precipitation late in the week as series of upper
disturbances pass with timing of light precipitation poorly
identified. Limited instability and forcing profiles suggest a low
risk of severe weather at this time.  Temperatures a bit of a
challenge as clouds will tend to be changeable and could easily
affect highs and lows by 5 plus degrees.

Monday...Skies to partly clear with any light rain to slide east
by mid-morning as cool front passes.  Trends suggest cool air to be
a bit delayed with highs upper 50s north to lower/mid 60s in the
south or about 10 to 15 degrees above normal.

Monday night through Tuesday night...A weak upper disturbance to pass
with a chance of light rain or rain/snow mix.  Local forcing tools
suggest American solutions are overdone on moisture and thus QPF
with trace to areas of a few hundredths suggested.  Temperatures at
surface are mild and limited evaporative cooling with light
precipitation should tend to keep any moisture that reaches the
ground to be liquid form.  Lows Monday night should be mostly in the
mid/upper 30s with highs upper 40s to lower 50s.  Tuesday night...
clearing with colder air supports 20s to near 30F far south.

Wednesday and Wednesday night...fair and cool with highs only in the
40s.  Increasing clouds with south wind suggest mins in the 30s with
potential for any precipitation likely delayed until Thursday.

Thursday...poor confidence with weak elevated upglide suggestive of
areas of light rain that would tend to keep with evaporative cooling
highs 45 to 55 with risk south areas highs too cool. Thursday
night...increasing moisture supportive of areas of rain and embedded
non-severe thunder with mins in the 40s.

Friday and Friday night...mild with cool frontal passage supportive
of unsettled weather of rain, rainshowers with embedded storms.
Still above average in variance in timing and location of surface
low track. Risk of severe weather, if any, are low due to limited
dry air and lower instability...this will be better known in next 12
to 24 hours. Most locations to receive light to moderate rain totals
are suggested for entire event Thu/Fri at this time. Temperatures
support mild highs mostly 60s on Friday ahead of front.  Lows mostly
in the 40s.

Saturday and Sunday...light precipitation ending Saturday and cooler
with highs mostly in the 50s and lows in the lower/mid 30s or near
seasonable.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
ISSUED AT 1236 PM CDT Sun Mar 19 2017

VFR weather will continue today, with gusty southeast winds at 10
to 20 kts. By this evening, increasing moisture along and ahead of
a low pressure system will bring scattered thunderstorms and a few
showers to locations mainly along and north of Highway 34 in Iowa
and western Illinois between the 05Z and 10Z period. After this,
there is potential for MVFR stratus development, and this could
impact much of Monday morning. For now, I have lowered CIGS to
around 3500 ft and will watch to see if post frontal stratus
threat is growing on satellite data.
ERVIN

&&

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

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...Nichols
AVIATION...ERVIN



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