Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
1137 PM CDT Thursday Apr 17 2014

Synopsis...
issued at 305 PM CDT Thursday Apr 17 2014

Low stratus that plagued the County Warning Area this morning has finally eroded
by early to middle afternoon. Middle/high level clouds were streaming
northeast across our southeast County Warning Area in advance of a digging trough in the
Southern Plains. Some light rain was noted on radar/surface
observations in southeast Kansas. 3 PM temperatures in the County Warning Area were in the upper
40s to middle 50s. A long wave trough was approaching from the west and
subsidence behind that had already cleared skies from the eastern
Dakotas and western Minnesota southward into western Iowa and northern Kansas.

&&

Short term...(this evening through friday)
issued at 305 PM CDT Thursday Apr 17 2014

Forecast focus on clouds and temperatures.

Tonight...I have removed mention of probability of precipitation for this evening in our
far southeast counties as the low levels of the atmosphere are
way too dry even to support sprinkles. In addition...the digging
trough/forcing in the Southern Plains tracks into the lower MS
valley. In our region...models swing a long wave trough across the
County Warning Area this evening followed by subsidence and clearing. At the
surface...high pressure will build into the area overnight
providing light winds. With the dry airmass will go near to a bit
lower than guidance and will forecast chilly minimum temperatures
ranging from the upper 20s at Independence to the middle 30s
southeast. If winds go calm for a time some locations may see a
bit colder readings than what is in the grids.

Friday...a pleasant Spring day anticipated to end the work week with
plenty of sunshine...rather light winds and warmer temperatures.
This will be due to a high pressure ridge over the region. The dry
airmass and stronger middle April sun should allow for a nice rebound
after a chilly start to the day. I will forecast maximum temperatures
in the upper 50s to middle 60s...which is normal for middle April. This
should be a welcome change after several days of below normal readings.

Long term...(friday night through thursday)
issued at 305 PM CDT Thursday Apr 17 2014

A slower frontal system over the weekend has trended the forecast
toward a warm...and mainly dry for the Easter Holiday. Building
upper ridge in a developing more amplified pattern will result in
above to possibly well above normal temperatures through the middle
of next week...followed possibly by a period of unsettled and
possibly stormy weather later in the week.

Friday night into Saturday...surface ridge axis currently over the
plains departs to the east allowing warmer air to return to the
region. Overnight...dry air and light southeast winds out of the ridge
axis...along with mostly clear skies should cool temperatures into
the middle 30s to middle 40s before an increasing pressure gradient begins
to stir winds toward morning. Saturday...the next low pressure
system forming over the plains will tighten up the pressure gradient
leading to at least 15 to 25 miles per hour south winds through the day.
Looking conservatively at mixing to near 850 mb...temperatures
should warm into at least the lower 70s over most of the area.
However...with the Gulf moisture return reaching into at least the
west...there could be some cloud cover to buffer the warming some.

Saturday night through Sunday night...the progression of the late
weekend system has slowed over the past several model runs...
possibly in response to a the blocking effects of a stronger slow
moving upper level low off the southeast coast. Other than a small
potential for elevated showers on the nocturnal low level jet
reaching the far west and northwest late Saturday night...both days
now look dry. Increasing moisture may lead to more cloud cover for
Sunday...but with the area remaining under continued warm air
advection and southerly surface winds...temperatures should again
reach at least the lower 70s. Will have low probability of precipitation for showers and
possible thunderstorms across the far west and north Sunday
afternoon into Sunday night...mainly to account
for potential changes in the timing of the weak cold front.
The current consensus model timing has this front not pushing
through until Monday...where the highest probability of precipitation are concentrated.

The large scale pattern continues to trend toward a more
amplified...blocky looking pattern for middle to late next week with an
upper ridge building over the central U.S. The next cyclone forming
over the plains advances slowly eastward Thursday and Friday increasing
chances for showers and thunderstorms in the moist...unstable...warm
advection well in advance. Our consensus forecast has chances as
early as Wednesday...but would not be surprised to see further
slowing delaying this by another day. This pattern will favor well
above normal temperatures and our current forecast showing highs in
the upper 60s to lower 70s with lows in the 50s will likely undergo
further upward adjustments over the next several days if confidence
in this setup increases.

&&

Aviation...(for the 06z tafs through 06z Friday night)
issued at 1133 PM CDT Thursday Apr 17 2014

High pressure over Minnesota will through WI overnight causing winds over the
middle Mississippi Valley to veer to the northeast then east by
Friday morning. The area of high pressure and the dry low level
air mass will keep VFR conditions over the area tonight. Friday...
winds will continue to veer the to the southeast but remain
light...as low pressure forms over the central/northern plains.
Conditions will remain VFR through Friday evening.

&&

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

$$

Synopsis...haase
short term...haase
long term...11
aviation...dlf