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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
256 am CDT Sat may 23 2015

Synopsis...
issued at 255 am CDT Sat may 23 2015

High pressure was entrenched across the area this morning. The
strongest high was located off to our east. This was leading to a
light easterly wind across our eastern area. High level moisture
lead to cirrus clouds across the area. This moisture was the
result of a south southwest flow at the upper levels. This flow
and ripples through the flow will be the dominate weather producer
through the Holiday weekend.

&&

Short term...(today and tonight)
issued at 255 am CDT Sat may 23 2015

Main forecast concern for the short term are the chances for
precipitation tonight. The precipitation gradient will be located
somewhere across the County Warning Area...making for a difficult forecast.

During the day today...high level clouds should persist. Warm air advection into
the area and insolation will help to increase temperatures across
the area today into the middle and upper 70s. A few sites may even
break the 80 degree mark. 500 mb ridging will move through the area
today and even through the overnight hours. The flow will then
turn south to southwest. This will lead to moisture advection
into the area. Today will be the last day of the weekend with no
probability of precipitation.

Tonight...500 mb ridging should occupy most of the County Warning Area through 12z.
This...should help to limit overall probability of precipitation for the night. Spectral
models suggest that we will see precipitation over most of the area from
6z to 12z Sunday am. The NAM suggests that most of the precipitation will
be west of the Mississippi River. Model reflectivity from the
wrfarw and wrfnmm supports this notion as well. As far as I can
tell...the NAM and and WRF models have a better handle on coverage
across the County Warning Area. This means that rain will likely stay west of
Mississippi River through 12z Sunday. A lack of instability
suggests that this will be mostly rain. I cannot rule out an
isolated thunderstorm with this flow. I put thunder in the
forecast for any area that has a chance or greater for precipitation.

Long term...(sunday through friday)
issued at 255 am CDT Sat may 23 2015

Near to slightly above normal temperatures and unsettled with periodic bouts of showers
and some storms.

Sunday and Sunday night...higher probability of precipitation targeting mainly western 1/2-2/3 of County Warning Area
especially Sunday am with veering low level jet and attendant moist advection and
convergence. Then...continued chances Sunday afternoon with moist axis (pwats
1.5-1.75 inches) and potential perturbations embedded in southwest flow aloft.
Perhaps secondary focus of higher probability of precipitation arriving Sunday night with shortwave trough
lifting into the upper Midwest.

Memorial Day and Monday night... more agreement that Memorial Day harbors a much
lower potential for precipitation as flow veers westerly ushering in slight drying and
shifting main moist axis to our east... while main forcing attendant to shortwave
trough lifting away from region. Thus Memorial Day overall should have many dry
hours... but warm and muggy conditions with highs around 80 or lower 80s and dewpoints
well in the 60s. Precipitation chances look to increase again Monday night as secondary
disturbance moves through the middle-Mississippi Valley... and attendant weak surface
cool front sags into the region by Tuesday am.

Tuesday through Friday... some indications of possibly another drier period developing
by Wednesday or Wednesday night with passage of weak front and increasing heights
aloft in wake of upper level shortwave. Pattern though looks to reload and turn active
yet again latter half of the week and just beyond with Gulf moisture increasing ahead
of another plains trough.

&&

Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1109 PM CDT Friday may 22 2015

An approaching storm system will bring south to southeast winds
around 10 kts by Saturday morning...but otherwise...the dry air in
place should keep any cloud cover well above 8000 feet...and likely
mainly cirrus through Saturday morning. Rain chances will begin
well after midnight Saturday night. Ervin



&&

Dvn watches/warnings/advisories...
Iowa...none.
Illinois...none.
MO...none.
&&

$$

Synopsis...Gibbs
short term...Gibbs
long term...05
aviation...Ervin

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