Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 251139
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
539 AM CST Tue Nov 25 2014

.SHORT TERM: (Today through Wednesday Night)
Issued at 325 AM CST Tue Nov 25 2014

West-northwest flow will continue through most of the day today
as a weak surface ridge tries to move into the Mississippi Valley.
Short range guidance is indicating that the clouds currently over
northeast Missouri and west central Illinois should clear out
during the morning. Expect temperatures to rise into 35-40 degree
range across most of the area under a partly to mostly sunny sky
today.

Meanwhile, shortwave upstream over Alberta will dive down into the
longwave trof over the central CONUS.  The surface clipper is now
forecast to dive southeast through the Missouri Valley tonight and
early Wednesday morning.  Guidance seems to be in pretty good
agreement that the surface low will be near Kirksville at around 18Z
Wednesday.  Low will continue off to the southeast into Kentucky
Wednesday night.  Mid-level shortwave energy combined with weak to
moderate frontogenetical forcing and even some upper level
divergence on the left exit region of an upper level jet streak will
combine to produce a band of precip which will affect areas
primarily along and east of the low track.  This will encompass most
if not all of our CWFA on Wednesday.  BUFKIT soundings from the NAM
and GFS do support mostly snow during the morning, with a potential
for mix of snow and/or rain in the afternoon.  Expect surface
temperatures to be near or just above freezing at the initial
outset with slowly rising temperatures through the day.  Current
thinking is that accumulations will be an inch or less, but this
could change quite a bit if the low shifts its track either to the
west or to the east.  Some lingering sprinkles or light snow will
likely continue over eastern areas during the evening, drying out
overnight with lows dipping back into the 20s.

Carney

.LONG TERM:  (Thursday through Monday)
Issued at 350 AM CST Tue Nov 25 2014

Cool on Thanksgiving Day behind Wednesday`s system as a 1035mb high
builds into the Mississippi Valley with highs struggling into the
low to mid 30s across most of the area.  However, the longwave trof
over the eastern CONUS will begin to translate eastward later
Thursday and Thursday night.  This pattern shift will set up a
warming trend for Friday and Saturday.  Southwest flow will prevail
both days which will provide us with increasing low level moisture
as well as warming temperatures.  Temperatures will rise into the
40s and 50s Friday and mid 50s to low 60s Saturday.  Both GFS and
ECMWF show some transient areas of light QPF on Saturday, but
believe this is the typical reaction to strong low level moisture
advection.  In most of these cases there is little if any actual
precipitation.  Another clipper moves across the Upper Midwest which
drags a cold front into northern Missouri Saturday night into
Sunday.  This front becomes quasi-stationary over our area which
will make temperature forecasting for Sunday and Monday quite
difficult.  Medium range guidance is in good agreement at this time
with the front dipping south Sunday night and Monday as a strong
high pressure system dips into the Northern Plains from Canada and
then shifts eastward across the Upper Midwest.  Both GFS and ECMWF
print out precip as the front moves south...looks like most likely
from over-running warm advection at 850mb.  Think chance/slight
chance PoPs in the MOS blend look good at this time with slowly
falling temperatures for Sunday through Monday.

Carney

&&

.AVIATION:  (For the 12z TAFs through 12z Wednesday Morning)
Issued at 530 AM CST Tue Nov 25 2014

Back edge of MVFR cigs (2-3kft) associated with cold air SC now
stretches from just W of KUIN to W sections of STL metro area, and
is moving southeast at ~ 20kts. Current rate of movement has all
of this cloudiness pushing east of the Mississippi River and
exiting UIN and STL metro area TAFs in the 13-15z time frame. VFR
conditions should then prevail for the rest of the day and into
the evening, with VFR mid clouds aoa 8kft thickening across the
area after 06z as cloudiness associated with upstream clipper
overspreads the region. Precip associated with the clipper should
begin to threaten UIN and COU just after 12z Wednesday, with this
threat moving into STL metro by mid-late morning.

Specifics for KSTL: Early morning MVFR cigs 2-3kft at start of
TAF period will advect east of airport complex by 14z, with VFR
conditions/mostly clear skies then expected for the rest of the
day and into the evening. Mid clouds in advance of approaching
system will move into the area during the predawn hours, with
cigs lowering to around 3kft as precip forms by mid/late Wednesday
morning.

Truett

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     38  29  41  29 /   5   5  70  20
Quincy          35  27  37  23 /   5  10  60  10
Columbia        39  30  40  25 /   0  30  50   5
Jefferson City  40  30  42  27 /   0  20  50   5
Salem           37  27  39  30 /   5   0  60  20
Farmington      40  27  43  29 /   0   5  50  10

&&

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

$$

WFO LSX





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