Area Forecast Discussion
Issued by NWS St. Louis, MO

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004
FXUS63 KLSX 081630
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
1030 AM CST MON FEB 8 2016

.UPDATE:
Issued at 1022 AM CST Mon Feb 8 2016

Have updated grids thru tonight to increase PoPs thru at least the
evening hours. With another vort moving swd, expect SHSN to
continue across at least the ern half of the CWA. Still do not
anticipate much accumulation with these showers, but a few spots
may see around an inch if some of the showers hit the same
locations.

Tilly

&&

.SHORT TERM: (Today and Tonight)
Issued at 300 AM CST Mon Feb 8 2016

Previous forecast is pretty much on track. Large scale amplification
is underway with lead shortwave centered through IL and initial
cold front well to the east. Secondary cold front/surge is through
KUIN/KPPQ and KCOU at 08z with the next weaker upstream vort max
stretching from the upper low in WI into western IA. This second
cold front will blast through the area this morning as the vort
max rotates s/se, accompanied by gusty northwest winds, strong CAA
and falling temperatures. Regional radars don`t seem to give
justice to the snow especially from northern MO into southern IA.
Snow showers, snow bands - they will spread southeast across the
area this morning in association with the aforementioned vort max
rotating southeastward. Model soundings continue to exhibit steep
low level lapse rates and strong unidirectional shear in the
lowest few km, supportive of HCRs/snow showers with conditions
becoming less favorable from north to south late morning into the
afternoon. Snow accumulations are not expected to be much and
could be highly variable with some spots seeing not much more than
a trace or dusting and others up to a half inch, and in highly
isolated spots possibly upwards of an inch. The potential for
light snow showers and/or flurries will continue this evening,
albiet lower, gradually shunting east of the MS River into IL
overnight as the upper low moves east into the lower Great
Lakes/Ohio Valley region.

Glass

.LONG TERM: (Tuesday through Sunday)
Issued at 300 AM CST Mon Feb 8 2016

The deep expansive upper trof will dominate the eastern 2/3rds of
the Nation through Wednesday resulting in winter cold with 15-20
degree below average temperatures. During the later half of the
week there is a general trend towards some deamplification of the
upper trof with a very broad cyclonic flow from the Rockies
eastward. Initially this will result in a slight moderation of
temperatures, however they will remain below average. The ECMWF is
supported by the GEFS showing another formidable surge of cold air
on Friday as the upper trof deepens again over the eastern U.S.
Confidence is high enough that forecast temps are now trended
colder for Sat/Sun. Still some questions on a precipitation event
Sunday into Monday. There is little run to run consistency in the
deterministic solutions and confidence is low at this point in
time.

Glass

&&

.AVIATION:  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 559 AM CST Mon Feb 8 2016

Large storm system centered over the Great Lakes will continue to
push cold air into the area on strong and gusty northwet winds.
Cyclonic flow around the upper system will also help produce bands
of light snow. Ceilings and visibilies will likely bounce a lot
today from VRF to occasional MVFR/IFR. With radar often not seeing
the band until it is on tip of a station, TAFs will be generic
with tempo lower ceilings/visibilities. Expect plenty of
amendments. Not much change expected into tonight with the snow
pretty much ending around 06z or shortly after.

Specifics for KSTL: Messy forecast for this period. Occasional
light snow with lower ceilings and visibilities will come and go
as the strong cyclonic flow around the upper system continues into
tonight.

JPK

&&

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

$$

WFO LSX



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