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Area forecast discussion...updated aviation
National Weather Service Saint Louis MO
1215 PM CDT Wed Oct 16 2019

Short term... (through late Thursday afternoon)
issued at 304 am CDT Wed Oct 16 2019

Surface ridge extending from eastern South Dakota south through central Kansas
will shift east-southeastward through our area tonight and
Thursday morning. Although the sky has cleared out across the
forecast area overnight behind the cold front, a large area of
low level cloudiness across IA, eastern Nebraska, and northwest MO
will advect southeastward into much of our area later this
morning and this afternoon, particularly for northeast MO and
west central Illinois. Continued low level cold air advection coupled
with only partial sunshine due to the cloud cover will result in
much colder high temperatures today. Highs today will be 10 to 15
degrees below normal for mid October. Most of this cloud cover
will shift east-northeast of the forecast area by late tonight
and Thursday morning. Cold lows in the 30s can be expected tonight
along with some frost due to good radiational cooling with the
surface ridge axis over the forecast area leading to light surface
winds coupled with low surface dew points in the 30s. Warmer high
temperatures can be expected on Thursday due to weak low level
warm air advection as the wind becomes southeasterly as the
surface ridge shifts east of the area. An upper level ridge will
also be shifting eastward into MO by Thursday afternoon. There
will be plenty of solar insolation as well with little cloud
cover expected. Although high temperatures will be warmer on
Thursday they will still be slightly below normal.


Long term... (thursday night through tuesday)
issued at 304 am CDT Wed Oct 16 2019

The warming trend will continue for the end of the work week with
continued southerly surface winds resulting in highs on Friday at
or slightly above normal. The chance of rain will return across
northeast and central MO by late Friday night as low-mid level
warm air advection increases ahead of an approaching shortwave
and weakening cold front. A southwesterly low level jet will also
bring increasing low level moisture into the area. This
precipitation will likely spread eastward into the rest of the
forecast area on Saturday, then shift east of the region by
Saturday evening. The European model (ecmwf) model has more quantitative precipitation forecast with this
relatively weak system compared to the operational GFS which does
not have much quantitative precipitation forecast left by Saturday afternoon. Will lean toward
the GFS solution with lower pops and less quantitative precipitation forecast Saturday afternoon.
It also looks like instability may be insufficient for any
thunderstorms late Friday night and Saturday. A tightening surface
pressure gradient will lead to strengthening southerly surface
winds and warmer highs on Sunday, likely into the 70s over much
of our area. A more significant precipitation event is expected
Sunday night and Monday as a deepening upper level low and
associated surface low move eastward across the northern plains
and drags a trailing cold front through our forecast area late
Sunday night and Monday. The GFS model is a little faster with the
progression of the cold front versus the European model (ecmwf) model. There
should be a band of showers and thunderstorms in the warm conveyor
belt structure ahead of the cold front which will translate
eastward across our area Sunday night and Monday. Colder
temperatures can be expected Monday night and Tuesday after
passage of the cold front with a deep upper level trough centered
over the Great Lakes region by Tuesday.



Aviation... (for the 18z tafs through 18z Thursday afternoon)
issued at 1206 PM CDT Wed Oct 16 2019

This morning's stratus has been a few hundred feet lower than
anticipated and has stubbornly remained just below 3kft across
much of the area. Fortunately, clouds are beginning to slowly lift
and scatter as expected. Given these trends, have decided to go
VFR right out of The Gate at all terminals, save for cou where the
stratus is a bit lower and is clearing more slowly. Guidance in
good agreement showing clouds slowly shifting east out of the
region later this afternoon and evening, so no ceiling concerns
beyond this afternoon at any terminals. Winds are expected to
become quite a bit weaker overnight tonight, and there are some
indications that radiation fog may develop across portions of
southern MO where winds will calm the most. That said, i'm not
confident that fog will actually develop, and if it does, the best
chances are south of the terminals. Therefore will not mention
visibility restrictions in any taf.



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