Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 292016
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
316 PM CDT MON AUG 29 2016

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 316 PM CDT Mon Aug 29 2016

Afternoon storms over eastern and central Missouri as well as west
central Illinois should diminish early this evening with the loss of
daytime heating.  This is reflected well in the last few runs of the
HRRR.  Then expect most of the evening and overnight hours to be dry
before showers and thunderstorms begin to redevelop late tonight
over northern Missouri and west central Illinois.  This will occur
in an area of weak low level moisture convergence ahead of a cold
front moving southward out of Iowa and northern Illinois.  This
front will continue to move southward during the day on Tuesday.  As
it does, have continued with high chance or likely PoPs over the
area.

Went close to MOS guidance for lows.   Continued to go warmer than
MOS for highs which is closer to persistence.

Britt

.LONG TERM...  (Tuesday Night through Next Monday)
Issued at 316 PM CDT Mon Aug 29 2016

The synoptic pattern at the start of the long term period
will feature a ridge across much of the west-central CONUS. However,
two PV anomalies, one sliding into the Pacific Northwest, and
another diving out of central Canada, will help knock down the
ridge through the middle of the week.

Main focus of the period will be on a cold front slated to move
through the region late Tuesday into Wednesday.  Convection will
occur along/ahead of this front Tuesday night into Wednesday.  Main
question will be on whether convection and convective debris lingers
through Tuesday night into early Wednesday, which could limit
destabilization ahead of the front Wednesday afternoon.  General
guidance consensus suggests that precipitation will wane late
Tuesday night which should allow for showers/storms to refire along
the front Wednesday afternoon/early evening. NAM/SREF/GFS/GEFS/ECMWF
solutions generally agree the preferred location for redevelopment
on Wednesday will generally be along/south of I-70, where pops have
continued to be nudged up a bit.  Despite a bit better low-level
focus and synoptic support, mid/upper level kinematic fields
continue to look weak which will limit the chances for any
organized severe weather with this fropa.

A very pleasant airmass will move into MO/IL behind the front for
Thursday and into Friday.  Have continued to keep temperatures just
on the warmer side of guidance, given the overachieving temperatures
as of late and the cool bias noticed in guidance with the last
fropa.  Even so, temperatures in the upper 70s/low 80s look like a
good bet Thursday into Friday.

Temperatures will steadily warm into the low/mid 80s through the
weekend, but the weekend continues to look dry.  A western trough
will amplify late this weekend which will help develop convection
across the Central Plains early next week, spreading into east-
central MO and west-central IL as early as late Monday and into
Tuesday. Given the amplified flow regime, would not be surprised if
this system continues to slow down in future model runs,

KD

&&

.AVIATION...  (For the 18z TAFs through 18z Tuesday Afternoon)
Issued at 1227 PM CDT Mon Aug 29 2016

Will continue to go with VCTS in all of the terminals this
afternoon as scattered thunderstorms have already developed across
central and eastern Missouri as well as west central Illinois.
These thunderstorms are expected to last through late afternoon
before dissipating with the loss of daytime heating. There maybe
some redevelopment of fog again tonight, but did not have enough
confidence at this time to add them into the taf.

SPECIFICS FOR KSTL: Added VCTS for afternoon thunderstorms which
have already developed west of the terminal. Expect these storms
to dissipate by sunset. Then expect dry and VFR conditions the
rest of the period.

Britt

&&

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

$$

WFO LSX



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