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000
FXUS63 KLSX 141157
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
657 AM CDT Fri Mar 14 2014

.SHORT TERM:  (Today)
Issued at 334 AM CDT Fri Mar 14 2014


Cold front as of 0700 UTC was oriented southwest-northeast from near KAMA
to KDYT and moving southeastward. This front should move through the area
late this afternoon with the main impact being an increase in mid
and high-level cloudiness. Colder air lags a few hours behind front so
temperatures should once again warm quite nicely. As we have seen on and
off the past several days...MOS guidance seems too cool and went several
degrees above warmer MAV guidance in many locations for today`s
highs which yielded 60s and 70s or around 15 degrees above seasonal
norms. Only reasons I did not get more aggressive was expected increasing
cloud cover mentioned above and possibility that frontal passage
comes in a couple of hours quicker than anticipated. Elevated fire
weather conditions will also be present this afternoon across
central...eastern...and southeastern Missouri as RH values dip to between
25 and 30 percent ahead of cold front along with 15-20 mph southwest
winds ahead of boundary.


Gosselin

.LONG TERM:
Issued at 334 AM CDT Fri Mar 14 20

(Saturday - Sunday)

Complex forecast for the Saturday - Sunday period. Two distinct shortwave
troughs will affect the region Saturday night/Sunday and their
interaction/attempt to phase will be key in determining
precipitation type and amounts. Right now...numerical guidance
suggests that these vorticity maxima will retain their unique
identities with the lead southern shortwave ejecting out ahead of
the longwave trough late Saturday night. Northern stream shortwave
will help push fairly strong baroclinic zone south of most of the
area by 1200 UTC Sunday. Track of low-level cyclone is well south of
the area...which climatologically is favorable for heavy snow.
However...with a fully phased system at this point not the most
likely scenario...rain will be rather slow to changeover to snow
given the lack of antecedant cold air. Still look for transition zone
to sink southward as strong CAA overwhelms warm boundary layer from
north to south between 0900 and 1800 UTC Sunday. Snow accumulations
will be very difficult to pin down as intensity of snowfall will
need to be sufficiently hard enough to overcome initially very warm
ground temperatures. Also plenty of uncertainty of how quickly
boundary layer cools although do think current model depictions are
very plausible as strong 1030+ hPa high is progged to be around the
Great Lakes with strong cold/dry advection persisting for a long
duration of time. For now...went conservative with snow amounts
given the uncertainty mentioned above and went with very low snow to
liquid ratios (~5:1 to 7:1) which yielded snow amounts in the
maximum band of 0.5 to 1.0 inches along and just to the north of
interstate 70.

With overcast skies and some from of precipitation falling during
the day...it will certainly be a raw/cold March day on Sunday with
temperatures in the 30s and 40s and stiff north winds 10-20mph
making it feel a whole lot colder. Temperatures in most areas will also
fall during the day.

(Monday - Thursday)

Another cool day is probable for Monday with highs generally in the
40s or 5-10 degrees below average. Next system to affect the region
will be on Tuesday with a chance of rain. Otherwise...mostly dry
weather is anticipated in the extended with temperatures near
seasonal normals.


Gosselin

&&

.AVIATION:  (For the 12z TAFs through 12z Saturday Morning)
Issued at 649 AM CDT Fri Mar 14 2014

Low level wind shear conditions will prevail until mid morning
with a 45 to 50 kt southwest low level jet screaming over the area
between 1000-2000 FT. While some stations are currently reporting
wind gusts, expect gusts to really pick up as daytime heating
mixes the lower atmosphere between 14-16Z. Gusts of 25 to 30 kts
are likely. A weak cold front will push through the area from late
morning through the afternoon which will shift the wind to the
northwest. Wind will diminish during the late afternoon into early
evening and become light and variable by 04-06Z. VFR conditions
are expected to prevail through the period.

Specifics for KSTL:

Low level wind shear conditions will prevail until mid morning
with a 45 to 50 kt southwest low level jet screaming over the area
between 1000-2000 FT. Expecting a direct crosswind from 210
degrees for a couple of hours this morning but the wind should
eventually become more west-southwesterly at about 250 degrees by
mid to late morning. Gusts will increase to around 25 kts after we
get a little heating and the lower atmosphere begins mixing. A
weak cold front will move through the terminal during the mid to
late afternoon shifting the wind to the northwest. Gusts will
diminish during the early evening. VFR flight conditions are
expected through the period.

Carney

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     69  39  69  37 /  10   0  10  60
Quincy          62  33  64  32 /   5   0   5  20
Columbia        67  36  69  36 /  10   0  10  60
Jefferson City  67  34  70  40 /  10   0  10  70
Salem           65  38  65  38 /  10   0  10  50
Farmington      70  35  68  41 /  10   0  10  80

&&

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

$$

WFO LSX