Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 230505
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1205 AM CDT Sat May 23 2015

.UPDATE:
Issued at 752 PM CDT Fri May 22 2015

Lots of echo on the radar mosaic this evening, but much of it is
deceptive, only showing up when the radar beam is at a certain
level--instead hitting the mid level clouds. However, the very
back edge of this echo in western MO is indeed hitting the ground
and has even measured .01" in a few places with KSZL the latest to
report sprinkles. These scattered showers are the product of
moisture convergence and being at the vanguard of the better
h850 moisture and further being aided somewhat by the eastern
extension of broadscale lift that is centered over the mid-MO
river valley.

This area is expected to advance E-NE and NE over the course of
this evening but will also move away from some of the better
moisture which spawned its early successes. Have added sprinkles
to the central and northeast MO forecast for mid and late evening
but do not expect any measurement with it expected to weaken some.
For now, have kept overnight dry with further weakening currently
expected.

Otherwise, temps on track for upper 50s and lower 60s for mins
thanks to mostly cloudy skies, which places it at or slightly
above the higher MOS values.

TES

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 339 PM CDT Fri May 22 2015

Upper level ridge is amplifying over the Mid-Mississippi Valley as
the trof over the western CONUS deepens.  Some of the last vestiges
of the Plains convection may make it into the area during the
evening, but the air overhead is quite dry and the upper ridge
should be providing some decent subsidence.  Expect little more than
a light shower or sprinkles if any of the precip actually makes it.
Otherwise, it should be a quiet night.  Lows should be much warmer
than this morning`s with increasing mid and high clouds and light
south-southeast flow.  MAV/MET numbers are within 1-2 degrees of
each other, and I see no reason to deviate at this time.

Carney

.LONG TERM:  (Saturday through Next Friday)
Issued at 339 PM CDT Fri May 22 2015

Upper level ridge continues to amplify through Saturday which should
keep a damper on convection across our area.  Main threat for rain
should stay over the Plains into western Missouri.  The ridge starts
translating east, putting the Mississippi Valley in deep southwest
flow Saturday night.  This will gradually increase our rain chances
as shortwaves ripple by.  Looks like several waves of showers and
thunderstorms will move through the area late Saturday night through
Monday.  Potential for heaviest rain still looks to be across
central and northeast Missouri into west central Illinois.  Medium
range guidance is in pretty good agreement that the primary
shortwave will open up and be pulled northeast late Monday, but a
secondary wave will move across the Great plains Monday night into
Tuesday.  While the chance for persistent rain will decrease as the
primary wave moves northeast, the secondary wave will likely produce
at least scattered showers and thunderstorms as it moves across the
area Tuesday into Wednesday.  The remainder of the week continues to
look warm with a chance of thunderstorms as we sit in southwest flow
aloft.  Temperatures look to be as much as 10 degrees above normal
in the mid 80s.

Carney

&&

.AVIATION:  (For the 06z TAFs through 06z Saturday Night)
Issued at 1054 PM CDT Fri May 22 2015

Mainly just VFR, mid-high level cloudiness through the period.
Could not rule out a brief sprinkle from mid level clouds, but it
appears that the more significant showers will remain west of the
taf sites. Light surface winds late tonight will become sely on
Saturday as the surface ridge over our region shifts well east of
the area.

Specifics for KSTL: VFR, mid-high level clouds through the
period. There may be a brief sprinkle, but the more significant
showers should remain west of STL. Light surface wind late tonight
will strengthen to around 10 kts from a sely direction by
Saturday afternoon.

GKS

&&

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

$$

WFO LSX






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