Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 151206
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
606 AM CST Mon Dec 15 2014

.SHORT TERM: (Today through Tuesday)
Issued at 305 AM CST Mon Dec 15 2014

The cyclonically curved north-south band of rain currently located
through central MO is associated with the warm conveyor belt and
is occurring in advance of a short wave rotating east-northeast
about the KS upper low. Present indications are this band will
continue advancing to the east-northeast this morning and be
centered through the St. Louis area around 12z and have exited the
eastern CWA by 18z. A distinct dry slot will move into the area in
the wake of this initial rain band, however additional development
is expected late morning-early afternoon through central MO tied
to another shortwave attendant with the northeastward lifting
upper low. There is also a pocket of rather steep mid level lapse
rates resulting from a cold temperatures aloft, and hence I have
added a mention of thunder during the afternoon through mid-evening
across northeast MO and west central IL as the upper low moves
from northeast MO into southeast IA. The vertically stacked system
will move into the lower Great Lakes by 12z Tuesday, sending a
cold front through the area tonight and keeping a chance of
rain/showers across primarily northeast MO and west central IL in
the cyclonic flow into the overnight hours. Gusty northwest winds
in the wake of the front will usher much colder air into the region.
The gusty northwest winds/strong cold advection and abundance of
clouds in the cold air on Tuesday will make for a blustery day with
steady or falling temperatures.

Glass

.LONG TERM: (Tuesday Night through Sunday)
Issued at 305 AM CST Mon Dec 15 2014

An active weather pattern will persist through the extended period
with several systems potentially impacting the area to various
degrees. Cold high pressure will dominate the area on Wednesday.
The models then track a low amplitude and deamplifying shortwave
through the MS Valley Wednesday Night into early Thursday. This
could result in some light wintry precipitation, primarily Wednesday
night across southern MO but confidence is rather low at this
point for anything more than chance pops. Another stronger
migratory trof/upper low and associated surface system is forecast
to impact portions of the lower-mid MS Valley in the Friday-Saturday
morning time frame. There are rather significant model differences
in the depth and positioning and amount of cold air, leading to
another low confidence forecast and only chance pops at this time.
Given the strength of this later system it certainly bears close
watching, and it might not be until Wednesday when it is well
sampled by the upper air network that we have a good handle on it.

Glass
&&

.AVIATION:  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 605 AM CST Mon Dec 15 2014

First batch of rain moving northeast through forecast area,
exiting taf sites by 14z-15z. IFR cigs/vsbys to improve to MVFR
as rain exits. Dry slot on back side of rain shield, so could see
cigs become scattered to broken for a few hours before wrap around
clouds/precipitation move back in by midday. Kept mention of vcnty
showers for tafs for this afternoon and into the early evening
hours. Otherwise, south winds to pickup with gusts to near 20kts
at times, then veer to the west as cold front moves through. Front
to move through KCOU by 23z Monday, KUIN and metro area tafs by 02z
Tuesday. MVFR cigs to persist through rest of forecast period with
gusty west to northwest winds.

Specifics for KSTL:
First batch of rain moving northeast through metro area, exiting
KSTL by 15z. IFR cigs/vsbys to improve to MVFR as rain exits. Dry
slot on back side of rain shield, so could see cigs become
scattered to broken for a few hours before wrap around
clouds/precipitation move back in by 18z. Kept mention of vcnty
showers for taf this afternoon and into the early evening hours.
Otherwise, southeast to south winds to persist, then veer to the west
as cold front moves through. Front to move through by 02z
Tuesday. MVFR cigs to persist through rest of forecast period with
gusty west to northwest winds.

Byrd
&&

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

$$
WFO LSX




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