Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 100820
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
320 AM CDT Mon Mar 10 2014
.SHORT TERM: (Through Late This Afternoon)
Issued at 302 AM CDT Mon Mar 10 2014
Look for another warm spring day with highs ranging from the mid 60s
to the lower 70s thanks to persistent southwest to west winds,
minimal cloud cover, and good diurnal mixing.
.LONG TERM: (Tonight through Sunday)
Issued at 302 AM CDT Mon Mar 10 2014
Today`s tranquil dry weather and above normal temperatures will
persist tonight and into Tuesday. Some cooler air is forecast to
backdoor into northern sections of the CWA during the afternoon
which will hold max temps in the 60s over this part of the CWA.
However, the unseasonably mild air will dominate the remainder of
the FA, and 70s should be common along and south of the I-70 corridor.
However, this winter just doesn`t want to let go, and it
it appears another round of wintry conditions are on the way for
parts of the CWA on Tuesday night. Anyway you slice it, after 3
very mild days the upcoming change on Tuesday night is going to be
dramatic, with strong northerly winds, sharply falling temps, and
rain changing to snow across much of the CWA.
The cooler air that works into northern parts of the CWA on Tuesday
will intensify the baroclinicity over the area, which in turn will
allow for rapid intensification of a surface low on Tuesday night as
a strong (and well-advertised) upper trof approaches the region. In
spite of the relatively mild temps of Tuesday afternoon, all of the
short range guidance indicates rapid lower tropospheric cooling
taking place Tuesday night as the storm intensifies/winds up, with
freezing levels dropping rapidly enough that the precipitation will
be changing over to snow. This type of situation...where ams cools
to critical levels in situ...is one of the more difficult snow
forecast situations, and in this case it is made even more
problematic due to 3 days of well above normal highs which will
generate some fairly warm ground temps.
While much of the qpf will fall with low level temps warm enough
for rain, 00z guidance continues to support earlier thinking that
greatest sustained precip with low level temps cold enough for all
snow will be over the northern third of the CWA, and rough
estimates of snowfall still suggest accumulations in the 1 to 2
inch range. It remains to be seen if snowfall intensity will be
great enough to overcome the melting due to the warm ground, but
these numbers still look like a good starting point.
Some minor accumulations are not out of the question as far
south as the I-70 corridor, but due to late changeover surmise
that any accumulations in this area will be spotty, and primarily on
It still appears that precip will wind down fairly rapidly Wednesday
morning, with windy and cold weather continuing throughout the
Temperatures should rebound fairly quickly during the latter half of
the work week. With a fairly strong southwest low level
flow/persistent warm air advection, and a good deal of afternoon
sunshine, expect highs to return to the upper 50s and lower 60s by
Colder air drops into the area next weekend as broad trof develops
over Great Lakes and New England. This will be followed by
shortwave dropping into the central CONUS from the Pacfic NW, with a
chance of precipitation with this feature in the Saturday
night/Sunday time frame.
.AVIATION: (For the 06z TAFs through 06z Monday Night)
Issued at 1049 PM CDT Sun Mar 9 2014
Little cloud cover expected late tgt through Monday evng, mainly
just some high level clouds. A surface ridge will remain across
the srn Plains and Gulf Coast states with a weak front sagging
into nern MO and w cntrl IL Monday evng. Swly surface winds will
continue through the period. Relatively strong wly winds are
expected late tgt/early Monday mrng at 1500-2000 ft in height, and
may include LLWS in the tafs during this time period.
Specifics for KSTL: Just some high level clouds this forecast period
with continued swly surface winds. The LSX VWP was indicating swly
winds around 45 kts at 2000 ft in height, although it may be
depicting the winds at this level a little too strong in magnitude.
Will include LLWS in the STL taf late tgt into Monday mrng.