Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 020218
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
818 PM CST Sun Feb 1 2015
Issued at 807 PM CST Sun Feb 1 2015
The arrival of colder temperatures has caused light rain to mix
with and finally change over to light snow across most of the CWA.
The overall forecast looks on track with only minor tweaks
required at this time.
.SHORT TERM: (Through Tonight)
Issued at 254 PM CST Sun Feb 1 2015
Focus continues to be the ongoing storm.
Dry slot continues to push into much of the CWA, resulting in
light RA or DZ. As colder temps advect into the region, precip
shud change to SN. It currently appears the 34 degree F isotherm
is the one to watch and see no reason this will change. Question
then becomes, how much precip will remain this eve as temps drop.
Mdls are in good agreement thru the period in all aspects except
for precip coverage/amount. All are suggesting ongoing def zone
precip will move esewd this eve and gradually dissipate, but
differ in timing. However, as much colder air is advected swd
behind the low, thermal profiles will be such that any clouds cud
produce at least flurries thru the night, despite loosing cloud
from the top down. The bulk of the measurable precip shud remain
over the nrn third of the CWA. Main question will be how far S the
measurable precip will progress.
Regardless, as winds increase and temps drop this eve, wx related
problems will likely continue. If SN is not blown off of
trees/power lines before it can freeze, power outages may become an
issue. Another issue to watch will be freezing of any water on roads
as temps drop this eve. This will obviously be a concern even for
areas that did not receive SN.
With precip still expected into early this eve and with other
concerns, will keep going headlines as is for now, but see no
reason attm that headlines will need to be extd.
.LONG TERM: (Monday through Next Sunday)
Issued at 326 PM CST Sun Feb 1 2015
(Monday through Wednesday)
Focus will be temps thru most of this period.
A chance for flurries will continue thru mid morning as clouds
continue to move swd. Otherwise, no precip is expected until Wed.
Mdls continue to be in good agreement thru much of this period.
Given the snow pack across nrn portions of the CWA, have trended
cooler across areas that received SN, especially at night. Tues
appears will be a good WAA day with decent thermal ridge advecting
into the area with swly sfc winds. Have trended twd the cooler
guidance across the N, but not below, while trending warmer
elsewhere. With a cdfnt moving in on Wed, potential for a large
error exists. Trended cooler across nrn portions where the cdfnt
will arrive either in the morning or during the day and trended
warmer across the S to account for a slower fropa.
This fnt shud also bring post-frontal precip to the region, tho
timing of precip and cdfnt is up for debate. The global mdls,
ECMWF/GFS/GEM, are in good agreement with the cdfnt being S of the
CWA by 00z Thurs. Have trended PoPs twd these solns as well. Any
precip shud be largely SN, tho, may have a brief period of RA/IP at
onset of precip.
(Thursday through Sunday)
Differences among mdl solns gradually increase thru the period.
Chance for SN continues from above early in the period. After a dry
period, the chance for precip returns on Sun as yet another trof
drops swd thru the region. Have kept PoPs low for this system as
mdls differ on timing, strength and thermal profile.
Otherwise, generally trended twd a compromise for temps thru the
.AVIATION: (For the 00z TAFs through 00z Monday Evening)
Issued at 454 PM CST Sun Feb 1 2015
Quick look at current conditions and models indicate a low MVFR
forecast. 18z Monday looks to be a good average time for improving
ceilings, although some gradual lifting will likely take place
from mid morning on. Light precipitation to continue for at least
another 6 hours, but do not expect major reductions in
visibilities. North wind gusting 25 to 30 knots to be a factor
overnight diminishing by 12z.
Specifics for KSTL:Surface observations and guidance suggest a low
MVFR forecast, so do not expect to see the current IFR to last.
Looks like MVFR conditions may hold until about 18z Monday as 925
MB relative humidity progs stay pretty high until then. Drizzle
should eventually transition to some light snow but do not expect
it to seriously drop visibilities. North wind with gusts 25 to 30
knots will pick up soon and prevail overnight dropping off by 12z.
MO...WINTER STORM WARNING until 9 PM CST this evening FOR Knox MO-
Lewis MO-Marion MO-Shelby MO.
WINTER WEATHER ADVISORY until 9 PM CST this evening FOR Monroe
MO-Pike MO-Ralls MO.
IL...WINTER STORM WARNING until 9 PM CST this evening FOR Adams IL-
WINTER WEATHER ADVISORY until 9 PM CST this evening FOR Pike IL.