Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 070039
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
639 PM CST SAT FEB 6 2016

.SHORT TERM:  (Through Late Tonight)
Issued at 225 PM CST Sat Feb 6 2016

Quiet wx is expected tonight. Southwest winds will begin to increase
slightly after midnight due to the tightening pressure gradient
ahead of an approaching surface trough. Mid/high clouds will also
increase ahead of an approaching disturbance. Overnight lows should
be 7-10 degrees warmer than last night due to a combination of a
warm start to the day, continued low-level WAA, and mid/high clouds.

Kanofsky

.LONG TERM:  (Sunday through Next Saturday)
Issued at 225 PM CST Sat Feb 6 2016

A decently strong and digging upper level disturbance will move
thru our region Sunday afternoon and early evening.  Despite the
strength of the lift from the clipper system, due to the initial
rather dry state of the column, it will take some time to
sufficiently saturate it to priduce any threat for pcpn.  It appears
enough comes together by late afternoon, principally for areas near
and south and east of the STL metro area, to justify maintenance of
low PoPs.  Current forecast handles the PoPs and areal extent well
with only minor adjustments made.  This first episode exits during
early Sunday evening.  Pcpn-types will be all rain and probably very
light at that, with minimal QPF.

The real meat of the leading edge of the Arctic air does not arrive
until late Sunday evening and will dominate our region into
Wednesday with below average temps.

Additional upper level disturbances are expected with this initial
arrival of Arctic air on late Sunday evening and overnight as well
as into much of Monday.  This upper level support and general deep
cyclonic flow over our area will be favorable for at least scattered
snow showers during this time, with some lingering into parts of
Monday night.  Due to what should likely be the banded nature of
these snow showers, accums will continue to be hard to nail down
until probably the day of the event.  In areas that receive these
bands, localized snow accums of 1", perhaps even 2", will be
possible.  Most locations, however, will receive just a dusting or
less.  The initial intrusion of this Arctic airmass will also be
accompanied by strong gusty northwest winds, cloudy skies, and
stagnant daytime temps on Monday as CAA remains strong thru the day.

There remains additional, yet weak, signals for clipper-like systems
late Tuesday and Friday within this otherwise prolonged period of NW
flow aloft, but not worth a mention yet with low confidence on
strength and track.

One thing we can say with more confidence is it does look like the
Friday clipper, whereever it tracks, will correspond with a new
outbreak of Arctic air across our region for next weekend with
continued favorable flow aloft for this.

TES

&&

.AVIATION:  (For the 00z TAFs through 00z Sunday Evening)
Issued at 634 PM CST Sat Feb 6 2016

Winds to persist from the southwest through tonight ahead of next
weather system. Will see high clouds on the increase. Frontal
boundary to move through KUIN and KCOU by 16z Sunday and STL metro
area by 18z Sunday. But with a lot of dry air to overcome, could
just see some light rain/sprinkles with it, so left mention out of
tafs at this time with just an AC deck moving in. Then on
backside of front, winds to pickup from the west to northwest
gusting to near 30kts by Sunday afternoon. Snow showers possible
but beyond the forecast period for the tafs.

Specifics for KSTL:
Winds to persist from the southwest through tonight ahead of next
weather system. Will see high clouds on the increase. Frontal
boundary to move through STL metro area by 18z Sunday. But with a
lot of dry air to overcome, could just see some light rain/
sprinkles with it, so left mention out of taf at this time with
just an AC deck moving in. Then on backside of front, winds to
pickup from the west to northwest gusting to near 30kts by 21z Sunday
afternoon. Snow showers possible but beyond the forecast period
for the taf.

Byrd
&&

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

$$
WFO LSX


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