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Area forecast discussion...updated aviation
National Weather Service Saint Louis MO
1118 am CST Thu Dec 12 2019

Short term... (through late Friday afternoon)
issued at 305 am CST Thu Dec 12 2019

Surface analysis early this morning is showing that a warm front
has moved north of St. Louis. Consequently, temperatures are
warmer than the have been the past few mornings with readings in
the 20s under increasing high clouds. These clouds were occurring
ahead of a weak shortwave trough currently over the Central
Plains. The weather is expected to remain dry through early
tomorrow as the atmosphere is dry through a deep layer. Highs
today will climb into the upper 40s and lower 50s given the
relatively warm start and the warm air advection. Lows tonight
will stay near freezing. There will be slight chance of rain over
northeast Missouri on Friday afternoon in advance of a trough that
will be digging into the Midwest. Highs again on Friday are
expected to be above normal.

Britt

Long term... (friday night through wednesday)
issued at 305 am CST Thu Dec 12 2019

Still appears that a upper trough will drop down across Missouri and
Illinois on Friday night into early Saturday with the GFS/European model (ecmwf)
bringing the attendant cold front across the County Warning Area late Friday night
and Saturday morning. Will continue with a chance for a light
wintry mix with this system as strong cold air advection moves in
behind the front. Still expecting little if any snow/ice
accumulations with at this point as the model forcing fields are
relatively weak and quantitative precipitation forecast amounts are light.

Guidance temperatures from both the gefs/European model (ecmwf) ensembles continue to
fall below normal behind the front. There continues to be a
considerable amount of uncertainty with the trough that will move
across the area early next week. The individual ensemble members of
the gefs and European model (ecmwf) eps continue to show a notable range in solutions
from north to south. This includes the 00z operational GFS which
brings the surface low track across the center of the County Warning Area on
Monday that would bring accumulating snow in the northern County Warning Area and
thunderstorms in the southern County Warning Area. The latest gefs brings its
surface low across northern Arkansas into the Ohio Valley and the
European model (ecmwf) eps is just south of it. I do have increasing confidence
that we will see precipitation Sunday into Monday night, so have
increase pops during this period. Precipitation type is still in
question as it may still be rain/snow or a wintry mix depending
where you are with some accumulation possible.

Tuesday into Wednesday still looks dry as large surface high moves
into the Midwest under deep dry layer. Forecast plumes from the
gefs mean and the cips analogs support below normal temperatures.

Britt

&&

Aviation... (for the 18z tafs through 18z Friday afternoon)
issued at 1118 am CST Thu Dec 12 2019

VFR conditions, dry weather, and southerly surface winds will
prevail at the taf sites through the valid period. Surface winds
gusting to 20-25kts will diminish by sunset with light (less than
10kts) expected for the remainder of the valid period.

Tes

&&

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

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