Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 261108
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
608 AM CDT SUN JUN 26 2016

.SHORT TERM... (Today and Tonight)
Issued at 306 AM CDT Sun Jun 26 2016

Like yesterday, the main focus today will be on convective trends
and coverage. The vast majority of convection thus far this
morning is centered through IA, with a small trailing portion in
NW MO which has actually shown a recent weakening trend. This
activity/MCS is being largely driven by a weak low amplitude
disturbance and 30+ kt southwesterly LLJ. I`m not sure whether
anything will bodily move into NE MO this morning, however there
is a rather apparent outflow progressing to the east/southeast and
this boundary combined with the LLJ should be enough to support at
least some scattered activity within the NW third of the CWA
through around 15z or so. The other quandry this morning is what
will happen across southeast and east central MO into southwest
IL. The overly wet GFS and some iterations of the HRRR have
showers and thunderstorms developing in this region between
10-12z. While I can`t totally discount this solution there is
currently a severe lack of clouds where the activity is expected
to evolve. Additionally the 10 member NCAR short-range ensemble
has only 1 member with any development and it is rather meager. At
this point I will carry some slight chance pops thinking some
spotty development is at least possible.

Otherwise it will be another hot and humid day with afternoon
heat indices in the 100-103 range across parts of eastern MO into
southwest IL. The main action is expected this afternoon. Morning
clouds that exist should thin and this should promote good heating
and a moderately unstable and uncapped air mass along and ahead of
an advancing cold front. The combination of convergence/lift with
the front and a more NE-SW oriented pre-frontal trof should lead
to the development of scattered to numerous thunderstorms from
central MO into central IL between 19-21z, with the activity
shifting to the south-southeast through the late afternoon and
evening hours along and ahead of the advancing boundaries.
Southern MO and southern IL will remain the primary area for
precipitation for the remainder of tonight. Can`t quite figure out
the NAM with all its precipitation across northern MO but the main
boundary will reside to the south.

Glass

.LONG TERM... (Monday through Saturday)
Issued at 306 AM CDT Sun Jun 26 2016

The initial front will continue to ooze south of the CWA on Monday
however the air mass remains quite warm in its wake and we should
see another seasonably hot day, albiet with less humidity. A
secondary cold front will then begin pushing into northern MO and
central IL in the afternoon advancing south of the area on Monday
night. Cooler and drier conditions will then prevail Tuesday and
Wednesday as a prominent surface high builds southward through
the central U.S..

An amplified upper air pattern will be in place at midweek
featuring a rather broad, deep upper trof over eastern NOAM and
upper ridge centered through western NOAM. The long wave pattern
remains status quo through the end of the week and into the
weekend with and northwest flow aloft dominating. Temperatures
should remain at or below average for late June-early July. We
will have to closely monitor a series of short waves within the
northwest flow Wednesday into Friday and potential impacts to MO
and IL. At this time it appears the first several in the series
will mainly impact parts of the central Plains into western MO. A
stronger short wave and attendant front will bring perhaps the
best threat of showers and thunderstorms in the Friday/Saturday
time frame.

Glass

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 601 AM CDT Sun Jun 26 2016

Generally VFR conditions expected through much of this TAF period.
A weak cold front will trigger scattered showers and thunderstorms
a KCOU and KSTL metro TAF sites beginning around 21Z. Coverage is
uncertain so only identified in TAFs as VCTS. Winds will become
light northwesterly this afternoon as well...then gradually veer
to northeasterly at KSTL by around 14Z Monday.

Specifics for KSTL:

Browning

&&

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

$$

WFO LSX



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