Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 132104
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
404 PM CDT Sun Apr 13 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 359 PM CDT Sun Apr 13 2014

(Tonight-Monday Night)

Main question tonight will be severe weather chances.  Large area of
stratiform rain currently over the CWA may suppress these chances as
latest SPC objective MUCAPE analysis is mostly below 500 j/kg except
across northern Missouri and west central Illinois.  The latest runs
of the HRRR has been trending toward weaker storms these evening
because weaker instability.  However, if the rain can mover out of
the area, there are very steep lapse rates over the Central Plains
that could help quickly destabilize the atmosphere ahead of the line
of the storms currently over eastern Kansas.  Deep layer shear
between 00-03Z will be between 35-50kts which will be sufficient for
organized severe storms.

Otherwise, forecast did not require too much changes as I still
expect front to march southeast across the CWA tonight.
Thunderstorm threat will end with the front and change to a plain
cold rain.  Have kept likely chances to for rain on Monday as the
ECMWF/GFS/NAM all mid-level frontogenesis moving across the region
during the day.  Also added likely chances over the eastern counties
on Monday evening as ascent from the mid level trough will not clear
the CWA until overnight Monday night.  Forecast soundings and
critical thicknesses still point to snow mixing with the rain from
northwest to southeast during the day on Monday.  Do not have any
accumulating snow at the moment as the low atmosphere will be rather
warm during the day, as will the surface temperatures after this
unseasonably warm weekend.

With the much colder air moving into the area, temperatures will
fall below freezing over the entire CWA on Monday night.  Many areas
will see temperatures in the mid to upper 20s.

Britt

.LONG TERM:  (Monday through Next Sunday)
Issued at 359 PM CDT Sun Apr 13 2014

(Tuesday-Sunday)

Upper trough will move east of the area by Tuesday bringing dry
weather for mid week.  While Monday night looks like the coldest,
Tuesday night will likely still have temperatures around freezing
before lows become more seasonable later in the week.

While the ECMWF has trended deeper and consequently slower with the
trough that will move through the central CONUS late this week, it
is still not as deep as the GFS or the Canadian GEM.  Will stick
with the more consistent ECMWF as the GFS is quicker to move the
front through the area on Thursday night than it was before.  Will
keep Thursday dry with the front staying to the northwest most of
the day with a chance of showers Thursday night and Friday as the
front moves across the area.  By next weekend, winds turn out of the
southwest quickly behind a retreating high allowing gulf moisture to
move north from the Gulf quickly into the area.

Britt

&&

.AVIATION:  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1257 PM CDT Sun Apr 13 2014

Latest weather trends shows band of rainshowers from IRK through
central Missouri and southwest into south central Missouri moving
northeast into eastern sections of the state. Narrow band of
thunderstorms entering west-central Missouri at this time shows
recent signs of slight weakening. More organized storms continue
to develop from TOP to ICT. Eastern Missouri and southwest
Illinois will continue to receive light rainshowers this afternoon
ending by 2100 - 2200 UTC. The stronger storms along far western
Missouri shows trend of continued weakening as it hit more stable
air over central Missouri. Will bring in rainshowers over
COU...UIN...and STL terminal from 1800 UTC and ending
precipitation between 2100 to 2200 UTC. The band of storms
entering far western Missouri may reach COU area around 2300 -
0000 UTC if it holds together.

Specifics for KSTL:
Band of rainshowers from north central Missouri through south
central Missouri will enter STL area after 1800 and should
end around 2100 UTC. Expect visibility restrictions of about 5
miles in light rain. The stronger convection over far western
Missouri may not reach STL since this system will be entering in
more stable atmosphere. Stronger storms over east central through
south-central Kansas is associated with the cold front. This band
of storms will be entering the STL area after 0400 UTC. Gusty
winds are likely with these storms. Surface winds will likely be
southwest at 15 kts with gusts to as high as 25 kts.

Przybylinski

&&

.CLIMATE:
Issued at 330 AM CDT Sun Apr 13 2014

RECORD LOWS FOR 4/15:

STL - 27 IN 1928
COU - 25 IN 1928
UIN - 24 IN 1928
FAM - 24 IN 1928


&&

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

$$

WFO LSX






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