Scientific Forecaster Discussion
Area forecast discussion...updated aviation
National Weather Service St Louis MO
1116 PM CDT Tue Sep 16 2014
issued at 845 PM CDT Tue Sep 16 2014
Going forecast looks on track this evening. Sky is clear/mostly
clear across the area with just a bit of cloud cover hanging in
across our southeast MO counties. Short range guidance continues to show
an increasing amount of low level moisture convergence over
eastern Kansas/western Missouri this evening with convection
breaking out between 06z-08z. Models are pretty consistent in
keeping all but perhaps a few showers out of our area through 12z
with the lion's share of the precip back over southwest Missouri.
Should see scattered showers and thunderstorms spread into parts
of central and eastern Missouri later Wednesday morning. Rap and
hrrr seem to want to bring some showers into northeast Missouri by
15z as well...and I may tweak the pops up before sending out the
midnight update if the new 00z NAM and GFS agree.
Short term: (through tonight)
issued at 230 PM CDT Tue Sep 16 2014
A weak S/W will approach the County Warning Area late tonight bringing a chance
for storms to wrn and srn portions of the County Warning Area late tonight.
Otherwise, expect clouds to continue to break up during the
afternoon and into the evening. Clouds are expected to build into
the region from the west tonight ahead of the S/W. Have trended twd
a compromise of guidance for wrn portions of the County Warning Area and twd the
cooler guidance for ern portions. Latest guidance suggests fog will
develop late tonight impacting srn and ern portions of the County Warning Area
where radiational cooling will be greatest.
Long term: (wednesday through next tuesday)
issued at 309 PM CDT Tue Sep 16 2014
(wednesday through friday)
Main concern continues to be rain chances tomorrow into tomorrow
night over mainly central and southeast Missouri. GFS/NAM/ECMWF are
still in relatively good agreement in dropping a weak shortwave
trough across Missouri during the day tomorrow. Each of these
models shows some weak low level moisture lingering across central
and southeast Missouri into Wednesday night, so will continue a
chance of showers and thunderstorms in this area. This scenario is
depicted pretty well at least through 00z by the reflectivity on the
NSSL WRF. Thereafter will maintain a dry forecast Thursday and
Friday as a surface ridge moves across the area at the same time a
upper ridge builds in from the west.
Went on the cooler side of guidance for highs the next couple of
days given the easterly surface flow and it matches up better with
mixing down the 900mb temperatures. Likewise followed the cooler
NAM MOS for lows.
(Saturday through next tuesday)
While there is still some disagreement between the GFS/European model (ecmwf)
regarding the speed and depth of a trough that will pass through the
area this weekend, it still appears that the attendant cold front
will move through on Saturday night and early Sunday. Will keep
chances of showers and thunderstorms going Saturday into Sunday.
Will keep Monday and Tuesday dry at this point as we will be on the
back side of the the upper trough, though the latest runs of the GFS
is showing a secondary through dropping down in the northwesterly
flow on Tuesday. This is a new trend that the European model (ecmwf) is not
showing. Still expect at or just above normal temperatures ahead of
the front on Saturday before they drop back below normal for early
next week given expected 850mb temperatures in the 6-9c
Aviation: (for the 06z tafs through 06z Wednesday night)
issued at 1104 PM CDT Tue Sep 16 2014
Northwest flow aloft will keep the mid fall like conditions in
place. Upper air wave will move through overnight to reinforce the
northwest flow. Models trying to generate precitation at the nose
of a low level (5000 ft) jet of 30 knots over the MO/Kansas border. So
far no sign of anything develping. Cou looks to be the only
location with a shot at rain, but will keep them dry for now. Band
of 4k to 5k clouds rapidly advancing southeast. That may put a stop to
any MVFR ceilings. Lower clouds over southern MO are slowly
expanding a bit to the north. Some fog at sus and cps will will
bring temporary MVFR conditions until the clouds arrive. Wednesday
looks to be VFR.
Specifics for kstl: 4k to 5k deck should arrive from 08 to 09z.
Will go with that and hold off on any MVFR ceilings. Lower clouds
over south central MO may work their way north and the mav
guiidance brings them in for a short time. Not that confident they
will arrive, so will leave out for now.
Weather forecast office lsx