Scientific Forecaster Discussion
Area forecast discussion
National Weather Service St Louis MO
326 PM CST sun Feb 1 2015
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 rain or dz. As colder temps advect into the region, precip
shud change to snow. 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 County Warning Area. 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 snow 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 snow.
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 warm air advection 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,
European model (ecmwf)/GFS/Gem, are in good agreement with the cdfnt being S of the
County Warning Area by 00z thurs. Have trended pops twd these solns as well. Any
precip shud be largely sn, tho, may have a brief period of rain/ice pellets at
onset of precip.
(Thursday through sunday)
Differences among mdl solns gradually increase thru the period.
Chance for snow 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 18z tafs through 18z Monday afternoon)
issued at 1126 am CST sun Feb 1 2015
IFR conditions will improve late this afternoon as surface low
pressure moves rapidly eastward. Expect visibilities to gradually
improve in snow at KUIN to MVFR by around 00z, and IFR ceilings in
the kstl Metro taf sites should lift to MVFR as winds shift to the
northwest by around 00z. Winds will increase rapidly at all taf sites as
surface pressure gradient tightens dramatically early this
evening. Expect gusts in excess of 30 knots at most taf sites.
Winds will diminish quickly on Monday morning however as low
pressure area continues to move away and surface high pressure
builds in. MVFR ceilings may begin to break up by 15z Monday as
drier air filters in.
Specifics for kstl: IFR ceilings should lift to low end MVFR by
around 23z as surface low pressure moves eastward. A period of
light snow will likely move through this evening, however
visibilities should remain above 3 miles. Very tight pressure
gradient behind the low will then move in early this evening and
produce strong northwest winds with gusts in excess of 30 knots. Winds
will diminish farily quickly by around 12z Monday, with MVFR
ceilings breaking by around 15z.
Preliminary point temperatures/pops:
Saint Louis 14 25 23 47 / 80 10 5 5
Quincy 8 19 17 36 / 90 5 10 10
Columbia 13 25 22 46 / 80 5 10 5
Jefferson City 14 26 22 48 / 80 5 10 5
Salem 14 27 21 42 / 50 10 5 5
Farmington 15 28 23 47 / 30 10 5 5
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.
Illinois...Winter Storm Warning until 9 PM CST this evening for Adams Illinois-
Winter Weather Advisory until 9 PM CST this evening for Pike Illinois.
Weather forecast office lsx