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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
650 PM CDT Thursday Aug 28 2014

issued at 209 PM CDT Thursday Aug 28 2014

The large area of rain and storms over central and western
Iowa...generally weakened this morning as the mesoscale convective vortex moved north of the
main moisture transport. In its wake...the trailing edge has become
the focus for in southeast Iowa into Missouri. We are
seeing heavy rain amounts from this line.


Short term...(this evening through friday)
issued at 209 PM CDT Thursday Aug 28 2014

Convection should continue to spread east and northeast this
afternoon...while the upper flow focuses west again for late night
storms. This should allow our event that is ongoing to end by early
evening in the east 1/2...while new storms fire well to the west.
There is some chance for storms to continue to sporadically fire up
on this outflow we will not go dry...but rather
isolated later this evening and overnight.

Friday will see many dry hours...before an active front approaches
from the west. This front may be delayed into Friday
night...resulting in a dry day for our County Warning Area. Either way...a low pop
is included to cover a chaotic flow ahead of the front with ample
moisture. The large synoptic wave driving the frontal rains should
mainly impact the region Friday night.

Temperatures should be moderated by clouds overnight...with lows in
the upper 60s to lower 70s...while fridays highs ahead of the front
should reach the lower to middle 80s. Certainly a warm and humid day.

Long term...(friday night through thursday)
issued at 209 PM CDT Thursday Aug 28 2014

The main forecast concerns in the long term period are potential for
additional rounds of heavy rain and/or severe storms Friday night
and again Sunday night into Monday.

The latest suite of medium range model guidance supports
widespread convection Friday night...spreading from west to east
across the forecast area. Support will come from a rather sharp
middle-level trough and significant moisture transport ahead of the
boundary...pushing precipitable water values close to 2 inches.
Have boosted probability of precipitation another notch...into the categorical range
across the northwest. Relatively meager deep layer shear should
keep the overall severe risk low...but would not be surprised if
we end up issuing a warning or two...mainly Friday evening.

Showers should be ending Saturday morning across the
east...followed by a mainly dry period Saturday afternoon through
Sunday afternoon. The next significant upper wave is forecast to
arrive Sunday night. Plentiful moisture and more favorable deep
layer shear should mean a more robust threat for severe addition to locally heavy rain. This wave is expected
to exit the region during the day on Monday.

Looking ahead...the operational GFS keeps more broad troughing
across the region...while the European model (ecmwf) suggests more of a zonal flow
with energy remaining north and south of the forecast area.
Low probability of precipitation from the consensus blend are reasonable at this point.


Aviation...(for the 00z tafs through 00z Friday evening)
issued at 646 PM CDT Thursday Aug 28 2014

Lingering low IFR and MVFR clouds mostly at Cid/dbq from today/S
rains will dissipate this evening with partly cloudy skies through
tomorrow afternoon. Hence...VFR conditions will dominate with a
chance for showers and storms...mainly after 29/18z as upper trough
passes...with the strongest cells producing MVFR conditionns in
moderate to heavy rain and bases of 1-3k above ground level. Southeast winds of 5 to 10 kts
to continue through late Friday.


Dvn watches/warnings/advisories...



short term...Ervin
long term...rp Kinney

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