Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 262100
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
400 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 it
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 18z TAFs through 18z Monday Afternoon)
Issued at 1230 PM CDT Sun Oct 26 2014

VFR through the period with increasing mid and high clouds. LLWS
is possible at KSTL/KSUS/KCPS/KCOU after 06z, ending around 13-15z
once diurnal mixing begins in earnest. Wind gusts of 20-30 kts are
possible tomorrow due to the stronger winds aloft that will be
mixed down to the surface.

Kanofsky

&&

.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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