Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 081731
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1231 PM CDT Tue Jul 8 2014

.UPDATE:
Issued at 734 AM CDT Tue Jul 8 2014

Showers and isolated thunderstorms associated with decaying MCS
have rapidly diminished early this morning, and based on latest
regional radar trends primary threat will be confined to far
southern sections of the FA over the next few hours. No changes
to the afternoon trends at this time, with primary threat of
redevelopment south of a Steelville-KCPS-Vandalia IL line. Zone
update out shortly.

Truett

&&

.SHORT TERM:  (Through Late This Afternoon)
Issued at 353 AM CDT Tue Jul 8 2014

The weakening MCS moving southeastward through east central and
southeast MO as well as southwest IL should shift southeast of our
forecast area later this morning.  The cold front now across
northwest MO will move southeastward through the forecast area
today.  Although we could not rule out redevelopment of convection
this afternoon along and just ahead of this cold front, it appears
that the effective low level boundary will be the outflow from this
mornings MCS which will be southeast of our forecast area this
afternoon.  The latest HRRR develops convection late this afternoon
south and southeast of the forecast area.  Even the operational
models afternoon qpf is confined to the extreme southern or
southeastern portion of our forecast area.  For now will include
chance pops across southeast MO and southwest IL, south and east of
STL for this afternoon.  High temperatures today will be slightly
cooler than yesterday due to at least weak cold air advection behind
the cold front and gradually lowering 850 mb temperatures.

GKS

.LONG TERM:  (Tonight through Monday)
Issued at 445 AM CDT Tue Jul 8 2014

It appears that the showers/storms will be south or southeast of our
forecast area by this evening as a surface ridge builds
southeastward into our area behind the cold front.  This will bring
cooler and less humid air into the region tonight and Wednesday.
Will have at least slightly below normal temperatures for tonight
through Wednesday night.  The next chance of convection will occur
over the northern portion of our forecast area late Thursday night
and Friday morning due to strong low level warm air advection and
moisture convergence on the nose of a southwesterly low level jet
ahead of a northwest flow shortwave.  The models were also depicting
relatively strong upper level divergence ahead of this shortwave.  A
warming trend will also begin Thursday night and Friday along with
increasing humidities due to southerly return flow on the backside
of the surface ridge as it shifts east of the region.  An upper level
ridge will try to build northeastward into southwestern MO Friday
night and Saturday.  Any potential for convection should be confined
to the northern and eastern portion of the forecast area as
shortwaves move east southeastward over the upper level ridge.
Temperatures should be quite warm this weekend, especially across
central and southeast MO.  There will be the chance of
showers/storms across the entire area as we head into the next work
week as the models deepen an upper level trough over the Great Lakes
region and send a cold front southeastward through our forecast area
Sunday night and Monday.  The ECMWF model is stronger or deeper with
this upper level trough compared to the GFS model and is also slower
moving the front through our forecast area and has more qpf
associated with this front.  Due to the model inconsistencies will
just include chance pops for most of the area on Monday along with
cooler high temperatures.

GKS

&&

.AVIATION:  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1220 PM CDT Tue Jul 8 2014

Current cigs will break up and become sct this afternoon. Expect
the remainder of the TAF period to be VFR. Winds will diminish and
back slightly this evening and become nwly again Wed morning. Only
expect diurnal CU Wed morning. Some guidance is suggesting that FG
may develop and impact UIN/COU late tonight. While the rainfall
last night may support this, believe enuf mixing will persist
tonight to prevent FG development.

Specifics for KSTL: VFR and dry conditions are expected thru the
period. Cigs are expected to quickly break up this afternoon with
winds remaining nwly this afternoon. Winds will diminish and back
slightly this evening and become nwly again Wed morning. Only sct
diurnal CU is expected Wed.

Tilly

&&

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

$$

WFO LSX






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