Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 031717
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1217 PM CDT THU SEP 3 2015

.UPDATE:
Issued at 1157 AM CDT Thu Sep 3 2015

Forecast remains on track with only minor tweaks to it for this
afternoon. As with previous days, there remains a very low chance
for an isolated shower or brief thunderstorm but probabilities
remain low enough to preclude mention.

Otherwise, plenty of sunshine with max temps in the lower 90s,
with mid 90s in the STL metro area, closely following persistence.

TES

&&

.SHORT TERM:  (Through Late This Afternoon)
Issued at 313 AM CDT Thu Sep 3 2015

Weak warm advection over central Missouri is producing isolated
showers northwest of Columbia.  Expect this activity to continue
this morning for a few more hours...but should be ending between 12Z
and 15Z as the weak low level jet backs and warm advection shuts
off.  Remainder of the day looks to be a carbon copy of the past
couple with high pressure controlling our weather.  Expect highs in
the 90-95 degree range.  Wouldn`t be surprised to see an isolated
thunderstorm or two this afternoon, but overall chances are 10
percent or less across the area so have kept the forecast dry for
today.

Carney

.LONG TERM:  (Tonight through Wednesday)
Issued at 346 AM CDT Thu Sep 3 2015

Stagnant weather pattern will persist at least through Sunday as the
upper level ridge remains locked in over the center of the country.
The trof currently over the Pacific Northwest will move east across
the Rockies into the northern Plains by late Sunday causing
cyclogenesis over the Dakotas.  Resulting cold front plows southeast
into Iowa by Monday.  As a result, the temperature and precip
forecast becomes a little tricky Monday through Wednesday.  While
Monday may be a repeat of Sunday with respect to temperatures,
medium range ensemble guidance trends pretty sharply cooler into the
low to mid 80s on Tuesday, even though we`re still in the warm
sector with the front hanging back across Iowa.  Upper 70s is being
advertised by guidance across northeast Missouri with low to mid 80s
further south on Wednesday as the front finally dives southeast into
our CWFA.  While I do think mid to high chance for thunderstorms as
indicated by guidance is appropriate for Monday through
Wednesday...not sure about the temperature forecast.  There isn`t
any airmass change until the front pushes through, and the low level
thermal ridge is still over our region with 850mb temps in excess of
+20C.  Low to mid 80s just feels too cool to me until the front
moves through...regardless of the precip chances.  If I was
forecasting in a vacuum, I`d keep temperatures at least 5 degrees
warmer than guidance; however, have kept the forecast temperatures
close to the ensemble guidance to maintain consistency with
neighboring offices.

Carney

&&

.AVIATION:  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1217 PM CDT Thu Sep 3 2015

VFR conditions, dry wx, and S-SW surface winds will prevail at the
TAF sites thru the valid period. Once again, we could see isolated
SHRA/TSRA for a brief period this afternoon but probs are much too
low for any TAF mention. Also looking at persistence being favored
for any VSBY reductions at some sites for late tonight.

Specifics for KSTL: VFR, dry, with S-SW surface winds.

TES

&&

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

$$

WFO LSX



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