Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 270853
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
353 AM CDT Fri Mar 27 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 331 AM CDT Fri Mar 27 2015

A potent northwest flow short wave has been generating an area of
light rain across western MO since late last night. This is far
removed from our CWA however there is some very light precipitation
now showing up in mid MO. Current projections would have this
across parts of the southern CWA after 12z and at this time I just
have a mention of sprinkles and flurries. It is moving rather
quickly due to the digging wave so anything that does occur is
expected to exit by 14z or so. Otherwise we should see alot of
clouds this morning and even into the early afternoon as low level
CAA continues, with a trend towards more cumuliform clouds as the
afternoon progresses. Once again a cold day with below average
temperatures for late March.

Glass

.LONG TERM:  (Tonight through Thursday)
Issued at 331 AM CDT Fri Mar 27 2015

Yet another robust short wave trof in the northwest flow will dig
southeastward thru the mid MS Valley late this evening into
Saturday morning. This wave looks even more potent than the
present one. The combination of large scale forcing/lift with the
short wave, strong low-mid level frontogenesis and low level WAA
will result in a band of snowfall. The center of this band looks
like it should be just west of the CWA, however snow will impact
portions of central and southeast MO. Since most of it will fall
at night, this will help the accumulation potential and presently
have amounts less than an inch. Saturday should be the last day of
the well below average temperatures.

Heights aloft begin to rise on Saturday night with the departure
of the eastern U.S. trof and surface high pressure retreats
allowing for low level WAA to get underway. Rather strong WAA
persists on Sunday ahead of the next cold front and this should
bring a rebound in temperatures back closer to normal. The WAA
associated lift along with ascent due to the migrating shortwave
will bring an area of pre-frontal showers on Sunday into Sunday
evening ahead of the advancing cold front.

Temperatures moderate back to above average next week as the
overall flow aloft decrease in amplitude and gains a more zonal
component. While there are some timing issues in the deterministic
models, another shortwave and attendant cold front will bring a
threat of showers and thunderstorms in the Wed/Wed Night time frame.

Glass

&&

.AVIATION:  (For the 06z TAFs through 06z Friday Night)
Issued at 1145 PM CDT Thu Mar 26 2015

Shortwave is sliding south southeast through western MO as of 04z
Friday with mid cloud deck moving into taf sites. Further north,
vfr sc deck on back side of system is sliding south towards
forecast area. How far south it will make it is hard to pin down.
For now have it moving into KUIN and KCOU over the next several
hours. As for precipitation with this system, light activity
remains west of forecast area so kept all tafs dry including KCOU.
Winds to pickup from the north by mid morning with sct to broken
diurnal sc. By late afternoon/early evening on Friday will see
winds veer to the northeast ahead of next shortwave that will
slide through region late Friday night.

Specifics for KSTL:
Shortwave is sliding south southeast through western MO as of 04z
Friday with mid cloud deck moving into taf sites. Further north,
vfr sc deck on back side of system is sliding south towards
forecast area. How far south it will make it is hard to pin down.
Winds to pickup from the north by 15z Friday with sct to broken diurnal
sc. By 00z Saturday, will see winds veer to the northeast ahead
of next shortwave that will slide through region late Friday
night.

Byrd

&&

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

$$

WFO LSX





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