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Area forecast discussion 
National Weather Service quadrant cities Iowa Illinois
352 am CDT Sat Jul 26 2014

Synopsis...
issued at 350 am CDT Sat Jul 26 2014

Isolated showers developed after midnight in our northern and
eastern County Warning Area on the nose of a 35-40 knot low level jet. There is
low level convergence and Theta-E advection but moisture is rather
limited which is preventing a more widespread event. These showers are
also occurring northeast of a warm front which extended across southeast
Iowa and into northeast Arkansas. 3 am temperatures ranged from the
middle 60s to around 70 with dewpoints ranging from the upper 50s in
northwest Illinois to the lower 70s in western MO. Extensive low stratus was noted
northeast of the warm front and covered much of our northeast half
of the County Warning Area. Skies were clear to partly cloudy in our SW County Warning Area.

&&

Short term...(today and tonight)
issued at 350 am CDT Sat Jul 26 2014

Forecast focus on severe/flash flooding potential and temperatures.

Today...any showers in our eastern County Warning Area will have shifted east of
the County Warning Area before 6 am so we will have a dry morning. Lamp data
suggests the stratus will linger across our northeast County Warning Area through
much of the morning with the low clouds then becoming scattered.
In our southern County Warning Area there will be plenty of sunshine south of the
warm front...which should advance to near Interstate 80 or so today.
This will set up a nice thermal gradient with maximum temperatures
along Highway 20 close to 80 while in our far south readings should
push to around 90. With dewpoints in our south rising into the
lower to middle 70s heat index values will soar well into the 90s to
near 100. Temperatures will need to be monitored closely today as
cloud cover (or lack of) will have an impact on these readings
just like yesterday...where readings were not as warm as I expected.

Severe weather...Storm Prediction Center has a moderate risk in our 4 southeast counties with
a slight as far north as Highway 30. Closed upper low in southern
Saskatchewan dives southeast into northern Minnesota increasing diffluence
across the Midwest and large scale ascent as height falls arrive.
The location of the severe weather and greatest concentration will
certainly depend on where the frontal boundary will exist and
amount of instability. The NAM seems too high with dewpoints and
convective available potential energy but nonetheless sbcapes should easily reach 4000 j/kg in our
south. How far north the severe threat is realized will once again
depend on cloud cover and frontal position. Models intensify middle
level winds to 50+ knots which will increase deep layer shear with
supercells initially developing later this afternoon in our south
as the cap weakens. Large hail and damaging winds will be the main
threat but a tornado or two is possible. Eventually this will
congeal into an organized mesoscale convective system with damaging winds the main threat
this evening as it eventually pushes well to the east of the County Warning Area.
For now have mentioned severe wording in the grids in our southern
County Warning Area late this afternoon into the evening hours.

Flash flooding...will need to keep an eye on the potential for
flash flooding especially in our far southern County Warning Area where 3 to 5
inches of rain fell yesterday. With high pwat's again this afternoon
and evening the potential is certainly there for torrential rain in
a short time. Some of the rivers also showed a rapid response to
this heavy rain but are still below flood stage at this time.

Overnight...a cold front will then push across the County Warning Area overnight
with minimum temperatures ranging from the lower 60s northwest to the
upper 60s southeast.

Long term...(sunday through friday)
issued at 350 am CDT Sat Jul 26 2014

Vigorous compact upper low is shown to dive southeastward through the
Great Lakes on Sunday. Attendant cold front will be sweeping through
County Warning Area early in the day followed by gusty northwest winds and lowering
humidity. Precipitation chances thus diminishing with faster frontal passage
and onset of subsequent cool...dry advection... but still held on to
small precipitation chances far north Sunday afternoon ahead of sagging surface
trough/wind shift over WI.

Mon-Fri...medium range models and ensembles in good agreement depicting
highly amplified upper air pattern with anomalously deep trough
over the eastern half of the Continental U.S. And a Sharp Ridge /heat dome/ out
west. This will keep area locked in northwest flow aloft resulting in
nice stretch of weather next week generally characterized by very
comfortable conditions with lower humidity and below normal temperatures...and
also drier with limited measurable rain prospects...with possibility
of a few PM showers mainly late week as airmass begins to undergo gradual
modification.

&&

Aviation...(for the 06z tafs through 06z Saturday night)
issued at 350 am CDT Sat Jul 26 2014

Occasional MVFR ceilings this morning north of Interstate 80 otherwise VFR
conds. Thunderstorms should develop this afternoon and into the
evening hours mainly south of Interstate 80. MVFR/occasional IFR conds
in thunderstorms. A warm front will push to near I-80 today.
Southeast to south winds south of I-80 with north to northwest to
the north. A cold front arrives tonight with winds becoming
northwest over all the taf sites.

&&

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

$$

Synopsis...haase
short term...haase
long term...05
aviation...haase

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