Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 311632
AFDLSX

Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
1132 AM CDT WED AUG 31 2016

.UPDATE...
Issued at 1131 AM CDT Wed Aug 31 2016

Small complex of showers and thunderstorms continues to move
slowly southeast across central Missouri late this morning. This
area is occurring in a band of 925-850 moisture convergence
underneath a MCV.  Expect this complex to continue to move to the
southeast with additional scattered thunderstorms developing ahead
of it this afternoon over east central and south Missouri and
southwest Illinois. With cooler temperatures advecting in from the
north and the clouds, highs in the low to mid 80s still look good
today.

Britt

&&

.SHORT TERM... (Through Tonight)
Issued at 220 AM CDT Wed Aug 31 2016

Despite the initially warm/humid start this morning, a cold front
is on track to move through the region today and ultimately bring
an eagerly anticipated cooler/drier air mass into the region
tonight.

Scattered SHRA/TSRA are expected to develop near and ahead of the
front today, especially during the afternoon when an upper trough
will be moving across the area. PW values remain relatively high
for this time of year, and some locations could experience heavy
downpours.

Pcpn will end with fropa, and a much cooler and drier air mass
then spreads into the region tonight. Overnight lows will be
around 10 degrees cooler than last night.

Kanofsky

.LONG TERM... (Thursday through Tuesday)
Issued at 220 AM CDT Wed Aug 31 2016

Expect cooler and drier post-frontal conditions for Thu, Fri,
and probably most of Sat. Friday in particular still looks like a
spectacular day. Temperatures will easily cool off at night given
the lower dew points, and overnight lows in the 50s are expected
across most of the area on Thursday night and Friday night.

A surface high pressure center located over the Great Lakes by
12z Fri will be the key factor in determining how quickly
temperatures start to warm up again and how quickly the chance of
rain returns to the area over the weekend after the upper pattn
transitions to southwest flow aloft. Initially, the sfc high will
ensure dry northeasterly to easterly flow across the area on Thu
night and Fri. Once the sfc high has progressed farther eastward
this weekend, return flow will begin over our area ahead of a
developing sfc low over the plains, bringing warmer temperatures
and increased rain chances to parts of MO/IL. Model runs 24hr ago
were in good agreement that return flow would begin on Sunday,
however the latest runs are slower with the eastward movement of
the sfc high. As the previous shift noted, this slower trend may
be due to a potential tropical system in the Atlantic which slows
the eastward progress of the sfc high and delays the return of
warm/moist wx conditions. The CR model blend depicts slightly
lower pcpn chcs for Sunday through Monday night, which seems
reasonable given the slower progress of the sfc high, and few
changes were required.

Kanofsky

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 659 AM CDT Wed Aug 31 2016

Plenty of stratus and fog dvlpd overnight due to moist conditions
and light winds. IFR/MVFR conditions should slowly improve and
become VFR at all sites by 15Z. Ongoing precip across wrn MO
should move into cntrl MO later this mrng and then expand in
coverage thru the day as a cold front approaches. Think KUIN will
be N of the bndry by the time precip would get going so kept TAF
dry. KCOU is closest to ongoing precip and according to guidance
stands the best chance of seeing addtnl SHRAs/TSTMs. Introduced
VCTS for the STL metro sites for a few hrs this aftn as the front
comes thru. IFR conditions are possible with the strongest
storms...but no way of telling this far in advance if any of the
terminals will be directly impacted. Winds are already nthrly so
won`t notice FROPA...other than falling dew points. Skies clear
from N to S this evng thru tonight with light nthrly winds
continuing.

SPECIFICS FOR KSTL:

MVFR conditions should improve by 15Z with SHRAs/TSTMs possible
this aftn as a cold front pushes thru. IFR conditions possible
this aftn if strong convection directly impact the terminal but
way too soon to be able to make that determination. Skies should
clear overnight. Light nthrly winds will continue thru tomorrow
with diurnal cu.

2%

&&

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

$$

WFO LSX


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