Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 211743
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1143 AM CST Wed Jan 21 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 239 AM CST Wed Jan 21 2015

Quiet weather is expected today. Look for highs in the 40s to near
50 degrees along with increasing clouds through the day.

Kanofsky

.LONG TERM:  (Tonight through Tuesday)
Issued at 239 AM CST Wed Jan 21 2015

Relatively uneventful January weather continues this week and into
the first part of the upcoming weekend. Several weak systems will
be passing nearby, producing little more than an occasional
increase in cloud cover. Expect daytime highs in the 40s to near
50 degrees at times and overnight lows in the 20s-30s.

The only system of note for our area over the next 7 days is a
clipper system which is forecast to drop out of Canada and into
the northern CONUS on Saturday night into Sunday. Widespread
precipitation is possible as this system moves from the northern
plains through MO and into the Ohio valley. Models are now
depicting a secondary vort max zipping through the back side of
the trough on Sunday night, therefore chc PoPs have been
maintained across the eastern CWA accordingly. A cooler air mass
then spreads across the region behind the departing clipper,
leading to seasonably cold temperatures from Sunday night through
Monday night. The precipitation type ought to be mostly rain on
Sunday followed by a changeover to snow on Sunday night with the
arrival of colder air. Expect further refinements over the next
few days.

Kanofsky

&&

.AVIATION:  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1131 AM CST Wed Jan 21 2015

Main fcst challenge will be determining sthrn extent of
stratus/stratocu field rotating around a low mvng across nthrn IL.
KUIN should keep MVFR CIGs thru most of the rest of the prd as the
terminal is embedded deep enough in the cloud shield to not see
much clearing until some time tomorrow. The bigger question is if
the MVFR CIGs will move into any of the STL metro terminals. The
cloud deck is just skirting the terminals to the north and the
trajectory of the clouds keeps the metro area on the SWrn fringe
of the clouds thru the aftn and evng...potentially thru the rest
of the night. Models indicate that as winds turn more Nrly
tomorrow mrng, the MVFR CIGs may finally push into the STL metro
area. If that occurs, then they may linger for a good portion of
the day but, that is far from certain attm and so this scenario is
not included in the fcst.

Specifics for KSTL:

Terminal will remain on the edge of an MVFR CIG cloud deck thru
the aftn and into the evng with CIGs 2.5-3kft. The edge of this
cloud shield may continue to graze the terminal thru the overnight
hours. Model guidance hints at a better chance of MVFR CIGs mvng
into the terminal tomorrow mrng as winds turn more Nrly but, this
is a low confidence solution attm and has not been included in the
fcst.

2%

&&

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

$$

WFO LSX





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