Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 020945
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
345 AM CST Mon Mar 2 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 345 AM CST Mon Mar 2 2015

Strong ridge of high pressure will move across Missouri into eastern
Illinois and western Indiana today.  Early morning fog should
dissipate within an hour or two of sunrise, and then we`ll see
increasing high clouds into the afternoon.  With wind turning to the
east and then southeast this afternoon and decent insolation, expect
temperatures to rise above freezing across most if not all of the
area.

Carney

.LONG TERM:  (Tonight through Sunday)
Issued at 345 AM CST Mon Mar 2 2015

(Monday Night)

Precipitation is expected to develop tonight in response to backing
flow aloft and increasing WAA.  The timing continues to look much
more favorable for after midnight for most locations, with the best
location for precipitation this evening being further west over
central and northeast MO.  While the strength of the warm air aloft
will be enough to result in liquid pcpn for much of the event
tonight, the northern fringes--especially northeast MO and
west-central IL--will likely also receive some sleet as well during
the first few hours.  The predominance of liquid pcpn will also make
surface temps a critical element in separating freezing rain from
rain.  The latest indicatons are that surface temps will be below
freezing for much of the CWA this evening, but with increasing
southeasterly winds and thickening cloud cover, temps are expected
to rise above freezing by sunrise Tuesday morning.  Freezing rain
should therefore be limited to a few hours or less for many areas,
resulting in a light glaze overnight, and be most persistent for
west-central IL, where ice accums may approach a tenth of an inch.
A Winter Wx Advisory was considered, but with the critical element
of surface temp and lesser impact of overnight occurrence, will let
the day shift take one final look with hopefully better surface temp
confidence before determining the need for any headlines.

(Tuesday)

Thick cloud cover is expected to persist but thanks to southerly
surface winds and rising temps from the previous night, temps should
still rise into the 40s for areas north of I-70 and should get into
the 50s for areas south of I-70.  This represents a bit cooler
forecast than thought earlier.  With this also looks like a bit less
of a thunder threat as well.  Have trimmed thunder to isolated in
coverage and pushed it south to just southern MO and far southern
IL.  A strong cold front will already be pushing into northeast MO
from the northwest by sundown.  WAA pcpn from the previous night
will continue for much of this day, gradually edging east but should
be all non-freezing liquid.  The much drier and colder air moving in
behind the cold front may briefly change any rain over to snow but
pcpn by this time should also be spotty and result in little-no snow
accums.

(Wednesday)

The models are coming into better consensus on handling another pcpn
event for this day.  Strong frontogenesis settling across the
southern half of MO and southern third of IL will couple with a
backbuilding h300 jet that will become cyclonically curved with time
to produce a decent shot of pcpn--especially for southeast MO and
far southern IL.  Enough cold air will be in place by this time to
maintain pcpn-types as all snow.  However, we continue to see a more
northward solution with the NAM, but the others are gradually
trending more northerly.  As far as amounts are concerned, there is
potential for a heavy snow event for parts of southeast MO given the
intense and deep lift that will occur here for several hours with a
sharp northern gradient also given the very dry air to the north.
Current snowfall amounts look to be just below 6" for a storm total
in parts of southeast MO and so will continue to monitor this
closely for the need to issue any winter headlines for this event.
Snowfall amounts further to the north towards STL metro are purely
arbitrary at this point with the anticipated sharp northern cutoff.

(Thursday - Sunday)

The main TROF axis aloft swings thru and shifts the flow from the NW
for the remainder of this period.  A quiet, dry period should
dominate much of this with moderating temps with southerly flow
expected for next weekend.  A shortwave TROF may deliver some pcpn
for next weekend but low confidence to say the least so left dry for
now.

TES

&&

.AVIATION:  (For the 06z TAFs through 06z Monday Night)
Issued at 941 PM CST Sun Mar 1 2015

VFR thru the TAF period. Cigs will lower gradually on Mon. Winds
will remain light thru the period and veer thru the period to
eventually become sely by Mon eve.

Tilly

&&

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

$$

WFO LSX



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