Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 150849
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
349 AM CDT Fri Sep 15 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 349 AM CDT Fri Sep 15 2017

An upper ridge will build across the area today ahead of a
developing low pressure system over the plains. Southerly winds and
rising heights aloft will contribute to yet another warm day today
with highs in the upper 80s to around 90. The tightening pressure
gradient between a surface high over the northeastern CONUS and the
developing low over the plains as well as good diurnal mixing
conditions will yield a few breezes across the area today. Overnight
lows should be a few degrees warmer than last night due to
increasing low-level moisture and persistent southerly flow.

Kanofsky

.LONG TERM...  (Saturday through Thursday)
Issued at 349 AM CDT Fri Sep 15 2017

Focus thru the forecast period will remain the above seasonal
average temps.

Period begins with upper ridge building into the region with surface
ridge anchored over eastern U.S. To the west, cyclogenesis continues
just lee of the Rockies as an upper trof traverses the Rockies. This
pattern leaves the CWA with sly surface winds and a veering profile
for Sat and Sun. As such, have trended temps with the warmer
guidance, some 5 to 10 degrees above seasonal average.

As the trof ejects the surface low into the northern Plains, expect
a cdfnt to drop into northern portions of the CWA. With sly to swly
flow thru the lower levels, do not anticipate the fnt being pushed
very far into the CWA as suggested by some prev mdl cycles. That
said, how far south of the fnt precip is expected differs among the
mdl solutions. Believe that the bulk of the precip will be tied
close to the front, but with outflow boundaries possible further
south, have kept PoPs to account for TSRA along these smaller
boundaries.

Have low confidence in PoPs beyond Mon due to a lack of agreement
among model solns. Have therefore kept PoPs low and continue thru
much of the forecast. However, models do generally agree with a sly
veering profile thru low levels thru the forecast period. Have
therefore continued an above seasonal average trend. That said, the
going forecast is not warm enuf if some periods of TSRA do not
develop.


Tilly

&&

.AVIATION...  (For the 06z TAFs through 06z Friday Night)
Issued at 1144 PM CDT Thu Sep 14 2017

VFR conditions, dry wx, and light SE-S surface winds will prevail
at the TAF sites thru the valid period. Crossover temps are too
low for much fog formation tonight except in areas SE of the STL
metro area and have no fog going at the TAF sites in this set.

TES

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     90  67  90  70 /   0   0   0  10
Quincy          88  64  89  67 /   0   0   0  40
Columbia        88  64  90  67 /   0   0   0  30
Jefferson City  88  64  90  68 /   0   0   0  30
Salem           87  62  89  67 /   0   0   5   5
Farmington      84  63  87  66 /   0   0   5  10

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX



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