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Area forecast discussion...updated aviation
National Weather Service Saint Louis MO
1145 PM CDT sun Sep 22 2019

Short term... (through late Monday night)
issued at 303 PM CDT sun Sep 22 2019

Early this afternoon, a surface cold front extended from central Iowa
into northwest MO, just west of Kansas City. Showers have developed
along this front, and it is anticipated, with the current
instability setup that thunderstorms will soon occur. Further east,
warm air advection and low level jet generated/sustained showers continue into much
of eastern MO and central Illinois. Temperatures ranged from the mid 60s
in northeast MO to the upper 80s in southern Illinois.

The warm air advection/low level jet batch of showers should progress through the
forecast area through early this evening, with the showers from the
cold front to try to fill in the gaps that are developing. All rain
should end around cold fropa, which will exit the southeastern
sections of the forecast area late tonight. Forecast rainfall
amounts are no longer enough to justify a flash flood threat and the
watch will be cancelled early. Min temperatures late tonight are
expected to dip into the mid 50s in NE MO to mid 60s in southern Illinois.

Dry weather is then expected on Monday and Monday night as high
pressure dominates. Max temps in the mid to upper 70s are forecast
on Monday, near normal for a change. Min temps on Monday night
should be a widespread 50s with around 60 in the stl heat island.

Tes

Long term... (tuesday through next sunday)
issued at 303 PM CDT sun Sep 22 2019

Until Friday, a broad-based upper level trough is expected to settle
over the north-central conus, keeping temperatures in check and
resulting in an unsettled weather pattern. This is especially true
in light of warm air advection developing late Tuesday and a surface cold front
dropping through the area on Wednesday, where mid-range pops are
currently forecast.

From Friday Onward, the CMC and ec aggressively build an upper ridge
back into our region while the GFS is more conservative. Either
way, it looks like above normal temps will make a return to our
region, it is just a matter of how anomalous they are. If the
ec/CMC solution verifies, temperatures will be much above normal
(pushing 90 in spots again) with a mostly dry forecast. If the GFS
prevails, it could be wetter with a front stalling over the area and
temps above normal but not by as much. For now, took a more middle
of the Road approach, leaning towards the ec solution but keeping
very low pops in for late week.

Tes

&&

Aviation... (for the 06z tafs through 06z Monday night)
issued at 1107 PM CDT sun Sep 22 2019

The front has pushed into the area, now with little more than
isolated to scattered showers along and in front of the front.
Precip will remain possible at each terminal until the front
pushes to the east, so will keep thunderstorms in the vicinity for the first few hours of
each taf.

As the front arrives, cigs are likely to drop into MVFR and remain
there until clouds associated with the front scatter out a few
hours later. A handful of upstream obs are even briefly dipping to
IFR before clearing out, though model guidance does not show this
well. Therefore, I will be putting an hour of IFR conditions at
cou and uin, with just sct009 in the stl Metro tafs where
confidence in IFR cigs is lower.

Bsh

&&

Lsx watches/warnings/advisories...
MO...none.
Illinois...none.
&&

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