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Area forecast discussion...updated aviation
National Weather Service Saint Louis MO
639 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 00z tafs through 00z Monday evening)
issued at 626 PM CDT sun Sep 22 2019

Widespread showers ahead of the front have largely cleared the
terminals. With those showers to the east of the terminals, we're
now just left with a few areas of rain ahead of the scattered
showers/isolated storms along the front in western MO. Thinking
shower and storm activity along the front will diminish with the
sun going down. With reduced shower and storm coverage, i'm not
confident any terminals will actually be hit with precip save for
cou. Therefore have gone with just vicinity showers until the
front arrives, and then vicinity thunder along the front. Included
prevailing showers for a few hours at cou given a higher chance
that storms stay together in the early evening. Left out thunderstorms in the vicinity at
uin where storms chances appear to be rather low.

Cigs should be at their lowest along and just behind the front.
Cool, dry air will then be advected in on the northwest winds behind the
front, helping clear the skies. There are some indications that
low stratus and perhaps fog may linger into mid morning, but
given the drier air and somewhat elevated winds expected through
the night, i'm thinking all terminals should be back to VFR by
12z. That said, given a chance that reduced conditions may linger
for a bit, have stuck sct025 in the Metro tafs to show this
potential.

Bsh

&&

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

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