Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 292335
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
635 PM CDT Mon Sep 29 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 315 PM CDT Mon Sep 29 2014

Another tranquil dry night on tap for the area. Weather features
we have been discussing the last few days remain the same. The
east-west cold front currently stretching across southern Wisconsin
into South Dakota will drop into northern MO and central IL
overnight in response to the digging trof moving into the Great
Lakes and downstream amplification. This front should reach near a
Columbia-St. Louis-Effingham line by 12z. Weak high pressure and
light winds will continue ahead of the front for a good part of
the night resulting in another round of overnight lows primarily
in the 50s.

Glass

.LONG TERM:  (Tuesday through Next Monday)
Issued at 315 PM CDT Mon Sep 29 2014

Not many changes needed to the previous forecast as it continues
to blend well with the latest thoughts and NWP guidance. Still
looking at a tranquil dry period Tuesday and Tuesday night. The
cold front will sag southward across eastern MO through the Ohio
Valley Tuesday as high pressure builds through the Great Lakes,
while retreating northward across the Plains region in response to
the migratory surface low. No sensible weather with the front
other than suppressing the temperatures a few degrees.

Active weather remains centered on the Wednesday night-Thursday night
period as the deep western upper trof progresses into the Nations
midsection. There are some questions initially Wednesday into
Wednesday night on the rate of eastward spread of precipitation as
the NAM and local WRF are quite a bit slower than the other operational
models. At this time I am favoring the more agressive GFS/ECMWF. An
intensifying and veering southwesterly LLJ and associated the pre-
frontal warm advection regime, along with weak impulses moving
across the region within the southwest flow aloft, would suggest
more progressive nature to the convection/MCS on Wednesday night.
Thunderstorms will remain likely Thursday/Thursday night as the
main short wave trof and attendant cold move across the region. Much
cooler weather remains on track in the wake of the cold front Friday
into Saturday with gusty northwest winds on Friday. Temperatures
return to seasonable normals on Sunday.

Glass

&&

.AVIATION:  (For the 00z TAFs through 00z Tuesday Evening)
Issued at 634 PM CDT Mon Sep 29 2014

VFR conditions with light and variable winds to persist through
the evening and into the overnight hours. Then a weak surface trof
to begin sinking south across forecast area on Tuesday. Winds to
become easterly behind boundary, especially for TAF sites along
Mississippi River.

Specifics for KSTL:
VFR conditions with light and variable winds to persist through
the evening and into the overnight hours. Then a weak surface trof
to begin sinking south across forecast area on Tuesday. Winds to
become easterly behind boundary after 18z Tuesday.

Byrd
&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$
WFO LSX





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