Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 082112
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
312 PM CST Sat Mar 8 2014
.SHORT TERM: (Through Late Tonight)
Issued at 311 PM CST Sat Mar 8 2014
Main concern in the near term will be rain/snow/sleet this evening
over the southern third of the CWA. Overall expect this to be a
light event with little if any snow/sleet accumulation. Light rain
currently falling over the southern CWA is part of a larger area of
precipitation that extends back to the west across southwest
Missouri into Kansas and Oklahoma. This is being forced by a 500mb
trough that extends from the western Great Lakes into the central
high plains that will move south of the area by midnight. Low
level thermal profiles from the RAP/HRRR suggest that this will
be mainly rain with snow/sleet mixing in as it ends from north to
south this evening.
.LONG TERM: (Sunday through Next Saturday)
Issued at 311 PM CST Sat Mar 8 2014
Dry weather is expected from Sunday into at least early Tuesday.
Surface winds will turn out of the southwest by midday Sunday and
continue into Monday providing a warmup wind under mostly sunny
skies. Forecast soundings show mixing up to 925mb on Sunday and
between 900-850mb on Monday and Tuesday which support the warmer GFS
MOS temperatures. Went will similar highs on Tuesday except across
northeast Missouri and west central Illinois where a cold front will
move into the area early in the day.
(Tuesday Night-Next Saturday)
A trough will drop down out of Canada and move across MO/IL on
Tuesday night and Wednesday. Both the GFS/ECMWF are showing
continuity problems with this fast moving shortwave which lowers
confidence in the timing of precipitation. Will keep a chance of
rain or snow going Tuesday night/Wednesday morning over the northern
CWA with a chance of rain elsewhere with this system. The cold
front that will move through the area on Wednesday will cause
temperatures to fall back below normal Wednesday into Thursday.
ECMWF/GFS are in agreement that low level flow will turn back
westerly by late Thursday with 850mb temperatures climbing back
above 0C which should allow for temperatures to warm back above
normal Friday and next Saturday. GFS and ECMWF both push a cold
front through the area next Saturday, but current indications are
that late next week will be dry.
.AVIATION: (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1116 AM CST Sat Mar 8 2014
Low end MVFR to IFR cigs and MVFR visbys continue to be widespread
across the region this afternoon. Surface high pressure building
in from the northwest will settle over the area tonight and winds
will become light and variable. Boundary layer moisture trapped in
the lowest 1500 feet will be difficult to clear out tonight given
weak flow, so will keep cigs and vsbys near to current conditions.
Will monitor closely for possible drops in both cigs and vsbys
tonight give some model guidance suggesting this as a possibility.
Light showers will pass south of all TAF sites this afternoon and
tonight. Cigs and vsbys should improve rapidly by mid morning as
stronger March sun works to mix out residual low level moisture.
Southwest winds will increase my midday as surface high slides off
to the east.
Specifics for KSTL: Low level moisture will be hard to dislodge
overnight as surface high pressure moves overhead and flow becomes
weak. Will keep both cigs and vsbys near current levels but will monitor
closely for indications of cigs and visbys lowering overnight as
indicated in a couple of the numerical models. Light showers will
pass well south of the KSTL TAF site this afternoon and tonight. Cigs
and vsbys will improve to VFR by late morning as sun mixes out low