Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 121833
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
133 PM CDT Fri Sep 12 2014

.UPDATE:
Issued at 1048 AM CDT Fri Sep 12 2014

Cloudy skies continue to cover the area this morning, though
there is less drizzle this morning than yesterday. The low clouds
will remain trapped under an inversion below 850mb and mid and
high level clouds are streaming in ahead of a mid-level through
currently extending from the Upper Midwest to the Central Plains.
Rain associated with this trough is already moving across northern
and western Missouri and will move into the area later today and
this evening which is already handled well by the going forecast.
Another day of low clouds and north/northeasterly winds will keep
temperatures from rising too much.

Britt

&&

.SHORT TERM:  (Through Late This Afternoon)
Issued at 340 AM CDT Fri Sep 12 2014

Could not rule out a little drizzle this morning from the persistent
stratus cloud deck across most of our forecast area.  An upper level
trough, strong shortwave will move eastward through the northern
Plains today and bring measurable rain to at least northeast MO this
afternoon.  Unseasonably cool weather will continue today as the
strong surface ridge centered across the northern Rockies and
northern Plains continues to build southeastward into MO.  The
850 mb temperatures will continue to fall, ranging from only about
2 degrees C across northeast MO to around 11 degrees C across
southeast MO by 00z Saturday.

GKS

.LONG TERM:  (Tonight through Thursday)
Issued at 340 AM CDT Fri Sep 12 2014

An interesting scenario for tonight, which is a carryover from
today.  A powerful shortwave TROF will track just north of our
region this evening and early overnight with much of the good
broadscale lift also passing to our north.  But...a lobe of
vorticity will trail to the south thru our region and maintain some
presence of this broadscale lift.  This combined with similar values
for moisture and deep lift thru the column currently found over
western Kansas where there is decent coverage of rain should result
in something more than what is currently depicted by many of the 00z
run models.  Needless to say, strongly favor the wetter MET MOS PoPs
for this evening, and in some cases, going even higher.  PoPs should
rapidly taper off after midnight as much drier air and clear skies
expand.

A strong Canadian surface high pressure--the same one that delivered
the cold air that helped blanket parts of western South Dakota with
snow 24 hours ago--will then build in for Saturday and continue to
dominate our region into Sunday.  This will maintain the well below
normal temp regime and promote dry weather after tonight.  Nighttime
min temps may dip into the upper 30s in spots--first across areas in
northeast MO early Saturday morning--and then again across the
eastern Ozarks of southeast MO early Sunday morning.  Strong
sunshine which can still be seen in September, especially before the
equinox, will result in large diurnal swings.  Prefer the warmer MAV
MOS for max temps this weekend.

The chance for rain will begin to return late Sunday night and
Monday as a cold front moves thru.  The airmass behind this front is
not quite as cool as the one we`re going to get this weekend and so
the resultant daytime max temps are only slightly below normal.
Models diverge on handling of precipitation chances after this, but
with decent agreement on northwest upper flow, prefer a dry solution
at this time.

TES

&&

.AVIATION:  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 133 PM CDT Fri Sep 12 2014

Ceilings are expected to gradually increase above 2000 ft this
evening. Some light rain is expected to move across the area into
this evening, with most of this rain moving across northern
Missouri into central Illinois. The most likely TAF to be affected
by light rain will be Quincy. Then drier air moving into the area
overnight which will cause ceilings to climb above 3000 feet from
north to south. Dry and VFR conditions are then expected at the
terminals after 09Z.

Specifics for KSTL: Ceilings are expected to climb above 2000 ft
this afternoon and then become VFR tonight. There is some chance
for light rain between 00-06Z, but confidence is not high enough
to include in the TAF at this time. Dry and VFR conditions are
expected after 09Z.

Britt

&&

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

$$

WFO LSX






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