Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service St Louis MO
348 am CST Mon Dec 29 2014

Short term: (through late this afternoon)
issued at 345 am CST Mon Dec 29 2014

Today should be another typical late December day with the County Warning Area
between two different systems. The previous cold front that pushed
thur the region on the 27th is still lingering across the sern US
with continued precip. Of importance to our area is the lingering
stratus that never completely cleared out of the sthrn zones last
night. Now that the low level flow has become Erly on the backside
of the sfc ridge, this cloud cover is pushing back into the ern
Ozarks from sthrn Illinois and the MO bootheel early this mrng. Not
completely sure how far northwest the clouds will make it before winds turn
nrly this aftn and push it back to the south. The other system is an
Arctic cold front that currently stretches from the lower tip of lk
Michigan to the Iowa/MO border and west along the Kansas/NE border. This bndry
denotes the wind shift and this should push thru the County Warning Area today. The
truly cold dry Arctic air lags behind this bndry considerably and
should arrive tonight.

2%

Long term: (tonight through sunday)
issued at 345 am CST Mon Dec 29 2014

(tonight-wednesday)

Guidance remains in fairly good run to run and model to model
agreement with the timing and intensity of the Arctic airmass that
will arrive tonight and remain over the region into midweek. Other
than a few minor tweaks to hourly temps tonight and into Tuesday
that try to reflect the impact of the Arctic air (falling temps
through at least mid morning Tuesday, followed by a very minimal
warmup in temps during the afternoon) haven't made any significant
changes to going forecasts. Certainly...the coldest temps will be
Tuesday night when overnight lows dip into the single digits and
teens...with highs on Wednesday only rebounding into the 20s. Have
continued mention of a few flurries with the arrival of the cold air
overnight tonight and into Tuesday morning.

(Thursday-sunday)

Medium range concerns remain focused on cutoff low that forms over
the West Coast over the next few days, and its evolution and
movement as it pushes into the central Continental U.S. By the end of the week.
As expected, each cycle of the medium range guidance continues to
slow the eastward progression of this system, with consensus now
suggesting the upper low will be over the Texas Panhandle by midday
Saturday...a full 12-18 hours slower than the solutions of yesterday
at this time.

In spite of the slow down, there still appears to be a threat of
precip across the area late Thursday night and Friday (as depicted
in current forecast), tied to the initial stages of warm air advection as the
Arctic airmass begins its retreat. The 00z GFS wants to keep most
of this precip south of our cwa, while the European model (ecmwf) pushes the northern
edge of the precip shield into northern sections of the County Warning Area by
Friday.

Other than this initial shot of precip well ahead of the system
(sometimes referred to as a "throat-clearing" for storms coming out
of the sw), lots of uncertainty remains with the eventual impact of
this storm on our County Warning Area. Trying to pick a particular solution at this
early juncture would primarily be speculation and/or "wishcasting"...
so plan to continue with a very broad brush approach with both pops
and ptype for now. The only real adjustment to ptype will be to
trend them a bit more to rain over southeast sections of the County Warning Area
after Friday morning into Saturday night as both GFS and European model (ecmwf) depict
a decent warmup of the air mass over this area. It will probably be several
more days (at least) before we get a better handle on this system.

Truett

&&

Aviation: (for the 00z tafs through 00z Monday evening)
issued at 523 PM CST sun Dec 28 2014

VFR and dry conditions expected thru the period. There is some
question of fog development overnight, mainly at sus and cou where
light winds and a clear sky will be in place. However, attm,
believe that any fog development will be patchy and will not
mention in taf. Otherwise, winds will become nely to Ely on Mon
and remain aob 8 kts.

Specifics for kstl: VFR and dry expected thru the taf period.
Light and vrb winds tonight will become nely on Mon and remain aob
8 kts.

Tilly

&&

Lsx watches/warnings/advisories:
MO...none.
Illinois...none.
&&

$$

Weather forecast office lsx

National Weather Service Glossary of Abbreviations