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afdlsx

Area forecast discussion...updated aviation
National Weather Service Saint Louis MO
527 am CST Thu Dec 14 2017

Short term... (through late tonight)
issued at 319 am CST Thu Dec 14 2017

Main focus thru tonight will be cloud cover, which will dictate
temps.

Low clouds currently covering the County Warning Area are expected to push south and
west thru the morning. As they do, a thick layer of mid and high
clouds are expected to spread over the area. With ample cloud cover
expected thru peak heating and cold air advection continuing thru the day, have
trended temps today twd the cooler guidance. With cloud cover
anticipated to persist thru tonight, have trended twd the warmer
guidance.

However, a fair amount of uncertainty exists regarding cloud cover
thru tonight. Expect breaks in the low clouds to develop today.
While fewer breaks in the high clouds are expected, thinner spots
are very possible, allowing more heating than currently expected.
This uncertainty continues into tonight, however, this is more
uncertainty due to differences in mdl guidance. Have trended twd a
more cloudy forecast and kept mention of flurries across nrn
portions of the County Warning Area.

Had considered removing flurries given the 00z guidance, but 06z
NAM just arriving wud suggest a chance of flurries still being
possible. Uncertainty remains how far south flurries is possible,
but kept confined to nrn counties. Otherwise, no precip is
anticipated.

Tilly

Long term... (friday through wednesday)
issued at 339 am CST Thu Dec 14 2017

A warming trend will begin Friday afternoon due to low-mid
warm air advection with surface winds becoming southwesterly. Much
warmer high temperatures can be expected on Saturday as an upper
level ridge shifts eastward into the central US, along with
southwesterly surface winds, and plenty of solar insolation with
little if any cloudiness. Highs on Saturday will be around 15
degrees above normal. Precipitation will spread northeastward into
our forecast area late Saturday night and Sunday morning with the
approach of a southern stream shortwave from the Southern Plains.
Models depict relatively strong upper level divergence ahead of this
feature. The precipitation type should be mainly liquid rain based
on the forecast soundings, although could not rule out a brief
period of snow mixed in with the rain late Saturday night and early
Sunday morning. Most of the precipitation should shift east of the
forecast area by Sunday afternoon. There may be patchy light
precipitation Sunday afternoon through Monday ahead of an
approaching positively tilted upper level trough. Most of this may
be just sprinkles or drizzle. It may get cold enough late Sunday
night that light snow or flurries will be possible across northeast
MO and west central Illinois. A surface ridge will build southeastward
into our area from the northern plains on Tuesday as northwesterly
upper level flow returns. Temperatures, particularly daytime highs
will continue above normal Tuesday and Wednesday with little cloud
cover. Upper level ridging and southerly surface winds will return
on Wednesday.

Gks

&&

Aviation... (for the 12z tafs through 12z Friday morning)
issued at 516 am CST Thu Dec 14 2017

Northerly winds will continue to diminish thru the morning and
gradually back to become wly tonight. Winds tonight are expected
to be aob 5 kts tonight. MVFR cigs will lift by late morning.
Broken to overcast clouds are expected thru the taf period.

MVFR cigs are expected to move back into KUIN late tonight. These
lower cigs may also be capable of generating flurries into Fri
morning. Have left out mention of flurries for now.

Tilly

&&

Preliminary point temps/pops...
Saint Louis 36 28 45 33 / 0 0 5 0
Quincy 32 24 40 30 / 0 10 5 0
Columbia 36 27 44 33 / 0 5 0 0
Jefferson City 37 27 45 32 / 0 5 0 0
Salem 36 24 41 30 / 0 0 0 0
Farmington 37 27 44 30 / 0 0 0 0

&&

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

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