Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 270423
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1122 PM CDT Sun Oct 26 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 355 PM CDT Sun Oct 26 2014

By most people`s standards today was a fine Autumn day, and this
enjoyable fall weather is going to continue overnight.   Warm front
stretching from near NW tip of MO into the bootheel has been working
northeast this afternoon and will continue to do so tonight,
allowing an unseasonably mild airmass to overspread the FA. This
mild air, combined with the advection of higher dewpoints and a
sustained southerly wind, should yield overnight lows from the
upper 50s to middle 60s...some 15 degrees above the average low
temps for late October. Cloudiness should be limited to a bit of
high level cirrus.

Truett

.LONG TERM:  (Monday through Next Sunday)
Issued at 355 PM CDT Sun Oct 26 2014

(Monday-Wednesday)

Strong upper trof pushing through the Great Basin Sunday afternoon
will progress east and work its way into Mississippi Valley by
Monday night, and all of the guidance is maintaining fairly good run
to run and model to model consistency with the timing and strength
of this system.  Mid and high level cloudiness will overspread the
area on Monday in advance of this system, but forecast soundings
indicate that the lower and mid troposphere will take a while to
saturate, so it may be that any precip over northwest parts of our
CWA will struggle to reach the ground until the afternoon hours.
Certainly the primary rain threat will be Monday night, as by this
time favorable upper level dynamics and low level forcing with the
approaching cold front will be able to interact with a sufficiently
moist airmass. Believe that most of the precipitation will be in
the form of showers, with a rather low chance of thunder due to
what appears to be mid level warm layer and modest mid-level lapse
rates.

On Monday, the progged thermal profile of the ams (model consensus
850mb temps of 18-20C) suggests an extremely warm day, and the only
impediment to a big warm up will be the increasing cloud cover.
Have pretty much stuck with going max temps which lean strongly to
the warmer MOS guidance, but am hesitant to go much warmer at
this point due to the rapid increase of cloudiness suggested by
the forecast soundings/RH progs. If clouds are slower developing,
these temps are likely too cool by a cat or so. Record max temps
don`t appear to be a widespread theme for tomorrow`s temps, but
STL record is certainly within reach. See climate section for
specifics.

The cold front will push into the Ohio Valley on Tuesday, sweeping
the rain threat out of southeast sections of our CWA during the
morning hours.  High pressure will then build into the central CONUS
and bring cooler temperatures to the entire area, with highs
dropping back to more typical late October levels on Tuesday and
then dipping into the 50s and 60s with the arrival of the coolest
air by Wednesday.

(Thursday-Sunday)

Medium range guidance indicates that an increasingly amplified but
progressive UA pattern can be expected from late this week into next
weekend.  There is good agreement that a secondary shortwave will be
dropping through the area on Thursday; initially on Thursday this
should produce a brief and modest warmup, but as it works east it
will deepen the trof over the eastern CONUS which in turn will bring
our area a reinforcing shot of cold air.  By the start of next
weekend this next round of cold air should result in some of the
coolest weather of the fall, with widespread frost possibly Friday
nights as lows drop well into the 30s, with Saturday`s highs only in
the low-mid 50s.

This cool down should be fairly short-lived, as upper ridge will
work into the area for the start of next week.  The temperature
moderation should begin on Sunday, with progs suggesting a more
substantial warmup occurring by the start of the new work week.

Overall, precip threat appears to be quite low during the medium
range, with the main concern tied to Thursday`s shortwave.  At
this point guidance is suggesting very limited moisture to work
with, so forecast will limit mention of precip to a smattering of
showers in a few locations on Thursday night.

Truett

&&

.AVIATION:  (For the 06z TAFs through 06z Monday Night)
Issued at 1042 PM CDT Sun Oct 26 2014

Warm front extending from a surface low over southeastern
Nebraska southeast through STL will lift northeastward late tonight.
Sely surface winds in UIN and the St Louis metro area will veer
around to a sly direction. Only some high level clouds expected
late tonight. A strong swly low level jet will lead to LLWS late
tonight and early Monday morning at the taf sites, with models
forecasting winds at 1500-2000 ft in height around 40-45 kts from
a swly direction. A relatively strong and gusty s-swly surface
wind can be expected on Monday as the surface pressure gradient
tightens up ahead of an approaching cold front. There will be mid-
high level cloudiness on Monday with scattered light showers
possibly developing in UIN and COU by late Monday afternoon. There
will be a better chance of showers Monday night as well as cloud
ceilings possibly dropping into the MVFR catagory as the cold
front moves southeastward through our area.

Specifics for KSTL: Just some high level clouds late tonight with
a sely surface wind veering around to a sly direction.
There will be some LLWS in STL late tonight/early Monday morning
due to strong swly winds at 1500-2000 ft in height around 40-45
kts. Mid-high level clouds on Monday with a relatively strong and
gusty sly surface wind. Showers will move into STL Monday night as
a cold front moves through the area with a dropping cloud ceiling
as the low levels saturate.

GKS

&&

.CLIMATE:
Issued at 355 PM CDT Sun Oct 26 2014

Record highs for 10/27:

STL    85 in 1950
COU    87 in 1927
UIN    84 in 1927


&&

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

$$

WFO LSX






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