Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 281741
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
1241 PM CDT Thu Aug 28 2014

.UPDATE:
Issued at 1230 PM CDT Thu Aug 28 2014

Have made some minor adjustments to going forecast into this
afternoon...mainly delaying the onset of PoPs across northeastern
Missouri and west-central Illinois. Beginning to have some doubts
as to what coverage of storms up that way may actually be...as
instability per latest SPC mesoanalysis is mainly to the south.
Will hold off and maintain mid chance PoPs up across the far north
for now but may need to lower later today. Further to the
south...scattered diurnal thunderstorms beginning mid-afternoon
looks on track as diurnal cu is already forming across
southeastern Missouri.

Gosselin

&&

.SHORT TERM:  (Through Late This Afternoon)
Issued at 334 AM CDT Thu Aug 28 2014

Nocturnal convection has remained well northwest of forecast area
with just a few very small showers popping up over northeast
Missouri and west central Illinois early this morning. For today,
will see a lot of sunshine initially but diurnal cu to pop by mid
to late morning most locations. So depending on how much cloud
cover forms and timing of when storms will develop will affect how
warm temperatures get. For now have highs in the mid 80s far north
to the upper 80s to low 90s elsewhere. Will still see dewpts in
the low to mid 70s so another very humid day. Heat indices could
get close to 100 in the metro area this afternoon but not warrant
any headlines. Just like yesterday, expect widely scattered
thunderstorms to develop along weak boundary that remains draped
across region.

Byrd

.LONG TERM:  (Tonight through Wednesday)
Issued at 334 AM CDT Thu Aug 28 2014

Tonight activity to slowly dissipate then refocus back to the
northwest along main frontal boundary. Lows tonight will be in the
low 70s. On Friday, upper level shortwave/trof to begin to lift
northeast out of central plains and into forecast area.
Precipitation chances to be on the increase with the best chances
Friday night and Saturday. Kept likely pops going through this
period. Highs on Friday will be a bit lower, in the upper 80s and
lows Friday night will be in the upper 60s to low 70s. As system
slides through on Saturday, the combination of clouds and storms
will keep highs in the low 80s far north to the upper 80s south.

Frontal boundary to stall out just southeast of forecast area
Saturday night through Sunday, could see a bit of a break in
activity with just isolated/scattered storms through this period.
Then an even stronger trof will slide east through region Sunday
night and Monday with increasing chances of storms once again. This
boundary to stall out just south of us as well, so kept mention of
storms possible through the rest of the forecast period. Highs will
be in the 80s through the middle of next week.

Byrd

&&

.AVIATION:  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1230 PM CDT Thu Aug 28 2014

Main focus for the valid TAF period will be on convection. Diurnal
thunderstorms are likely to develop by mid afternoon with the best
chance of affecting the St. Louis metro terminals. Kept a VCTS for
now at KUIN...though beginning to have doubts about coverage of
storms that far north as instability is mainly confined to areas
to the south. Tonight should be mainly dry...as diurnal convection
weakens and dissipates by 0100-0300 UTC. Some models are
developing more showers and storms along and east of the
Mississippi River tonight but left mention out of TAFs for now due
to low confidence. During the day tomorrow looks like a better
chance for showers and storms to redevelop as a midlevel system
approaches form the west.

Specifics for KSTL:

Main focus for the valid TAF period will be on convection. Diurnal
thunderstorms are likely to develop by mid afternoon. Tonight
should be mainly dry...as diurnal convection weakens and
dissipates by 0100-0300 UTC. However...some models are initiating more
showers and storms along and east of the Mississippi River tonight
but left mention out of TAF for now due to low confidence. During
the day tomorrow looks like a better chance for showers and storms
to redevelop as a midlevel system approaches form the west so
added a VCTS mention for that possible activity.

Gosselin

&&

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

$$

WFO LSX






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