Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 302259
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
559 PM CDT TUE AUG 30 2016

.SHORT TERM...  (Through Late Wednesday Afternoon)
Issued at 308 PM CDT Tue Aug 30 2016

Active thunderstorm complex has moved south to I-70 with the outflow
pushing to the south.  Still expect these thunderstorms to continue
to push south and east through late this afternoon and evening
before they diminish with the loss of daytime heating.  Chances
tonight will continue as there will be weak low level moisture
convergence ahead of the surface cold front coming down from the
north.  There will be some weak mid level support from a mid level
trough that will move into the area from the north.  The chance for
thunderstorms will continue into tomorrow over the area before they
begin to end from the north as drier air begins to filter in behind
the front.

There may be some fog over the area tonight with the abundant low
level moisture over the area.  MOS temperatures look reasonable
tonight and tomorrow.

Britt

.LONG TERM...  (Wednesday Night through Next Tuesday)
Issued at 308 PM CDT Tue Aug 30 2016

The actual airmass change will begin taking place on Wednesday night
as drier air filters south.  Think there will likely be scattered
convection continuing on the dew point boundary during the
evening, but there probably won`t be enough convergence on the
boundary to sustain precipitation after 03-06Z with the loss of
diurnal heating. Dew point temperatures should fall into the 50s
and lower 60s as high pressure builds across the Upper Midwest and
Great Lakes region. Persistent low level northeast to easterly
flow will keep cool and dry air over the region through the end of
the week and probably through Saturday as well. Temperatures
should be below normal with highs in the mid to upper 70s and lows
mainly in the mid 50s to around 60.

Guidance is indicating that the high will be trying to move off the
East Coast on Sunday (possibly slowed by a tropical system), but it
should be far enough east that we get back into return flow.
Southerly flow persists through the end of the forecast period
Tuesday afternoon.  Air temperatures and humidity will be more
typical of mid August with highs climbing back into the mid 80s by
early next week with dew point temperatures rising back into the mid
and upper 60s.  GFS and ECMWF print out precip Monday and
Tuesday...primarily over northern portions of the area, but there
are differences in the mass fields of the two models so this is low
confidence at this time.

Carney

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 534 PM CDT Tue Aug 30 2016

The current showers/storms in the St Louis metro area should
shift east/southeast of the taf sites by 00Z Wednesday. Could not
rule out some additional development of showers/storms impacting
the taf sites for the remainder of the night with the actual cold
front still north of the area, but most of the convection this
evening will likely be south of the taf sites. Will get some fog
late tonight/early Wednesday morning due to a light surface wind,
high surface dew points, and recent rainfall. There may also be
some patchy stratus clouds as well. There will be scattered
convection mainly during the afternoon on Wednesday as the cold
front drops southward through the region which could impact COU
and the St. Louis metro area. North-northwesterly surface winds
will strengthen on Wednesday.

SPECIFICS FOR KSTL: The current showers/storms in the STL area
should shift east/southeast of STL by 00Z Wednesday. Could not
rule out some additional development of showers/storms impacting
STL for the remainder of the night with the actual cold front
still north of the area, but most of the convection this evening
will likely be south of STL along outflow boundaries from
afternoon convection.  Will get some fog late tonight/early
Wednesday morning due to a light surface wind, high surface dew
points, and recent rainfall. There may also be some patchy stratus
clouds as well. There will be scattered convection mainly during
the afternoon on Wednesday as the cold front drops southward
through the region which could impact STL. North-northwesterly
surface winds will strengthen on Wednesday.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     72  85  64  81 /  40  40  10   0
Quincy          69  82  58  78 /  40  30   5   0
Columbia        69  81  60  78 /  40  40  10   0
Jefferson City  70  83  62  80 /  50  50  10   0
Salem           71  84  61  80 /  40  50  20   0
Farmington      70  83  61  78 /  40  50  20   0

&&

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

$$

WFO LSX



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