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000
FXUS63 KLSX 080225
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
825 PM CST Fri Mar 7 2014

.UPDATE:
Issued at 825 PM CST Fri Mar 7 2014

A cold front moving through our region is currently situated from
near a PPQ-COU line at 02z. Temps have slipped to near 40 in
northeast MO while remaining in the 40s and 50s south of the
front. Thick hi clouds have taken hold of our region resulting in
mostly cloudy skies areawide. Radar echo exists over western MO
but this is associated with lowering mid cloud at this time.

Hi-temporal res models continue to focus on ability of increasing
broadscale lift and WAA at mid levels to eventually generate some
light spotty pcpn mainly for areas north of I-70 late this evening
and overnight. Fortunately, it appears that much of the measuring
pcpn, which should be pretty meager to begin with, will be as
rain. However, enough evidence exists of spotty/spitty pcpn in the
wake later tonight to maintain a 20pct chance. It will be after
09z when temps are at or just below freezing, beginning with
northeast MO, where some very light FZRA or sleet will be
possible. Much like the thinking from the previous shift, there
is still plenty of uncertainty as to whether anything will occur
even at all and thus only the 20pct pops. This area of potential
for this light spitty wintry mix will expand into parts of central
MO and west-central IL around or just after daybreak for a very
brief window.

Based on recent temp trends, what should be a slow moving front
and thick cloud cover inundating the area more quickly, prefer the
warmer MET MOS temps for mins tonight.

A quick look at some of the new 00z guidance shows rain potential
for the I-70 corridor Saturday afternoon looking shaky with
better support for southeast MO and far southern IL but left the
forecast as-is for now.

TES

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 329 PM CST Fri Mar 7 2014

Warm advection ahead of a mid-upper level trof currently over the
Rockies will continue tonight.  Still seeing a chance of
precipitation tonight...mainly after midnight over northern sections
of the CWFA and spreading down into parts of central Missouri before
sunrise.  Forcing is pretty weak though and MOS pops are quite low,
so am only keeping chance/slight chance pops for tonight.  Thermal
profiles still look too warm for snow across the northern portion of
the CWFA, so have reintroduced a sleet/freezing rain mix.  Not even
sure if anything will actually fall, so accumulations will not be
mentioned at this time.  Temperatures will be tricky as the cold
front which is currently over Iowa moves across the area.  It`s
likely that northern sections of the CWFA will see falling
temperatures this evening after FROPA while southern zones may
steady out early and possibly remain nearly steady for much of the
night.  Stuck pretty close to MOS for lows which puts northern zones
near or just below freezing and keeps the rest of the area above
freezing.

Carney

.LONG TERM:  (Saturday through Next Friday)
Issued at 329 PM CST Fri Mar 7 2014

(Saturday - Saturday Night)

The cold front will move slowly south Saturday morning, but
temperatures should rebound a bit...expecting highs well above
freezing across the entire area.  Precipitation now looks likely
during the afternoon primarily along and south of the I-70 corridor
as the shortwave moves overhead.  Low level temperatures indicate
that the majority of the precip should be rain, but cold advection
behind the front, and falling dewpoints aloft will allow for the
possibility of some snow primarily Saturday night.  Cold advection
continues Saturday night with temps falling back into the 20s.

(Sunday - Tuesday)

Warming trend still looks on track for Sunday into the first part of
the work week.  Weather should be tranquil with relatively dry
northwest flow aloft and zonal flow in the low levels.  Surface flow
from the southwest will bring warmer air from the southern Plains
back into the Mid-Mississippi Valley and temperatures are expected
to be around normal on Sunday in the low 50s, and then warmer then
normal in the mid 50s to mid 60s on Monday and Tuesday.

(Wednesday - Friday)

Primary concern in this period is a longwave trof which is forecast
to dig across the Central U.S. developing a surface low over the
eastern Plains or Mid-Mississippi Valley.  Current indications are
that the majority of the precip will fall as rain, but as
temperatures fall late Wednesday/Wednesday night the rain could
change to snow before ending.  Thursday and Friday look tranquil,
with temperatures near or slightly below normal.

Carney

&&

.AVIATION:  (For the 00z TAFs through 00z Saturday Evening)
Issued at 513 PM CST Fri Mar 7 2014

Minimal changes to the prev TAFs. Fnt still expected to push thru
the region tonight. Area of MVFR cigs may lag the fnt slightly
initially. Winds will become nly behind the fnt. Main question
with this forecast is what, if any, precip will occur. At UIN,
precip is still expected to be very light, and may be more FZDZ
than RASN. At COU, guidance is beginning to suggest all precip may
miss the terminal just to the south. For SUS/CPS, no changes are
expected attm. Will continue to monitor trends.

Specifics for KSTL: No major changes to the prev TAF. Fnt still
expected to push thru tonight. Winds will become nly behind the
fnt. Cigs will be difficult with areas of high and low MVFR cigs
expected around the area. Otherwise, RA shud move into the area
late Sat morning into the afternoon hours.

Tilly

&&

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

$$

WFO LSX