Area Forecast Discussion
Issued by NWS St. Louis, MO

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000
FXUS63 KLSX 020333
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
933 PM CST Sun Mar 1 2015

.UPDATE:
Issued at 929 PM CST Sun Mar 1 2015

Have updated sky cover trends through late this evening as low
stratus has advected into the far southern CWA. Mid to high-level
cloudiness remain anchored for the moment across the far north. In
between...skies have become clear or mostly clear.
Consequently...temperatures are beginning to plummet with
light/variable winds. Have taken a stab at minimums tonight and
lowered them a couple of degrees where skies are expected to
remain clear the longest. Still expect an increase in mid/high
level clouds everywhere late tonight as quasi-zonal flow aloft advects
in clouds currently over KS/OK. Still probably am not cool enough
in some areas...and will watch trends through the remainder of the evening.

Gosselin

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 405 PM CST Sun Mar 1 2015

W-E oriented band of precip continues to weaken along the I70
corridor, and dont expect much of this to linger past 00z.

Otherwise, it should be a dry night across the area. Clouds should
thin with time as mid level trof swings into the area and slowly
drags somewhat colder and drier air southward. Did not go too
cold at this point as it appears that some mid or high level
cloudiness will be streaming into the area after the lower clouds
clear, especially over the southern/southwest half of the CWA.
Based on this cloud trend have have gone with lows from the teens
north to the lower 20s south, but if clearing is more pronouced
these will likely be too warm.

Truett

.LONG TERM:  (Monday through Next Sunday)
Issued at 405 PM CST Sun Mar 1 2015

(Monday-Wednesday)

Southward push of colder air overnight will reintensify surface
ridge, with the surface high then pushing through the mid-Mississippi
Valley during the day on Monday. This should mean a chilly but
tranquil day, with highs in the lower to middle 30s.

Active weather rapidly returns to the region Monday night as
return flow intensifies on the back side of the retreating surface
high. 12z models are in good agreement with earlier solutions
that intensifying isentropic ascent/WAA will cause another round
of wintry weather to develop. Although there could be a very brief
period of snow, primary ptype will be a mix of sleet and
rain/freezing rain. There could certainly be some sleet and minor
ice accumulations depending on how long surface temps remain below
freezing, but any ice should quickly melt early Tuesday as
surface temperatures rapidly warm through the 30s.

We should quickly...but briefly...have a taste of more spring-like
weather during the day on Tuesday, as warm air surges into the
region ahead of surface low that tracks from mid-Missouri Valley
into lower Michigan. As we get into the warm sector sensible
weather trends should be a bit more spring-like with showers
overspreading much of the area. Have continued a mention of
thunderstorms as well, but at this point instability looks fairly
meager.

We rapidly swing back to cold season mode Tuesday night and
Wednesday, as yet another surge of cold air works its way into the
Mississippi Valley. Ptypes will transition back from rain to snow
overnight Tuesday night as colder air undercuts the moisture, but
really not expecting much in the way of accumulation as precip
should end as freezing levels drop enough to support snow.

However, the pattern that is expected to develop by midweek is
certainly a bit more worrisome from a winter weather point of
view, as deeping trof from the western Lakes into the southern
Plains will allow pockets of energy and moisture to work east into
the cold air that is building into the region. All of the 12z
solutions suggest a band of precip developing from AR into the
lower Ohio Valley during the day on Wednesday, but there is
considerable disagreement in where this axis...and especially
where the north edge of this precip...will set up. 12z NAM was
very far north with its QPF placement and it was such an outlier
I have disregarded its solution for now, and have used a consensus
of GFS and ECMWF for PoPs at this time. Another round of
accumulating snow will certainly not be out of the question for
our area depending of course on where the aforementioned band of
precip develops.

(Wednesday night through Sunday)

Midweek system should be exiting the area Wednesday night with
just some lingering light snow over southeast Missouri and
southern Illinois. As strong surface ridge builds in, colder air
to slide south into region with lows in the single digits to mid
teens.

Sunny conditions return to the region on Thursday, but a lot of cold
air in place. Will only see highs in the upper teens to low 30s.

Surface ridge to move off to the southeast Thursday night allowing
southerly winds to return. Temperatures to begin moderating with
highs in the 40s for the rest of the extended.

Truett/Byrd

&&

.AVIATION:  (For the 00z TAFs through 00z Monday Evening)
Issued at 535 PM CST Sun Mar 1 2015

Any MVFR cigs are expected to dissipate over the next hour or two.
Remainder of the TAF period is expected to be VFR with winds aob 8
kts. Winds will gradually veer overnight and on Mon as a sfc ridge
moves ewd across nrn portions of the area. High to mid level cigs
will gradually lower late tonight into Mon morning.

Tilly

&&

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

$$

WFO LSX






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