Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 182257
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
557 PM CDT WED MAY 18 2016

.SHORT TERM...  (Through Late Tonight)
Issued at 340 PM CDT Wed May 18 2016

Sfc ridge will remain in control of the weather pattern thru
tonight. With the sfc ridge axis building into the region tonight,
winds will become light and vrb across much of the area.

The diurnal CU that has developed today is expected to dissipate
with sunset. This shud leave much of tonight clear. However, there
is an area of congested CU down stream of Lake Michigan that has
developed today. Guidance is suggesting that this area of moisture
will move into the region tonight. Exactly what the coverage of any
clouds will be is a little uncertain, but believe sct coverage is
most likely attm.

As for temps tonight, given the above, have trended aob the cooler
guidance for tonight. Do not with dewpoints mixing out into the
lower 40s across the region, do not anticipate fog development
tonight.

Tilly

.LONG TERM...  (Thursday through Next Wednesday)
Issued at 340 PM CDT Wed May 18 2016

Sprawling high pressure centered over the Great Lakes region will
continue to be the primary feature controlling our weather for the
next several days.  The second interesting feature to watch will be
the mid-upper level wave over Arizona which will opening up and
moving east across the lower Mississippi Valley Friday night.  This
wave will ultimately move over the southeast CONUS and amplify the
longwave pattern over the East Coast.  As the wave passes over the
Mississippi Valley it will move over the area of strong low level
baroclinicity over the Gulf Coast region which will force low level
cyclogenesis.

Model guidance is in pretty good agreement that the
low level circulation will move across eastern Arkansas into
Tennessee and Kentucky early Friday morning.  This appears to be a
bit further east than previous forecasts...and latest guidance has
the vast majority of the precip further southeast than previous
runs.  With the surface ridge still in place across our area and a
subsequent lack of low level moisture, have trended lower for PoPs
Thursday night and Friday.  As the longwave pattern amplifies Friday
night and Saturday, the surface ridge will retrograde westward from
the Great Lakes back into the Mississippi Valley.  This should set
up a good omega block aloft for the weekend with ridging through the
depth of the troposphere.

Ridging starts breaking down Monday into
Monday night which will bring the chance for rain back to the area.
Medium range guidance is in pretty good agreement on the timing of
ramping up PoPs for Monday night into Tuesday...but I`m a little
skeptical.  Models are typically too fast in breaking down blocky
patterns.  Would not be surprised to see the block hang in longer
than currently forecast.  Temperatures through at least Sunday will
be near or a few degrees below normal.  However, as the block breaks
down and southwesterly flow redevelops over the region, expect temps
to bounce back up to several degrees above normal.

Carney

&&

.AVIATION...  (For the 00z TAFs through 00z Thursday Evening)
Issued at 556 PM CDT Wed May 18 2016

Dry and VFR conditions are expected through the period as high
pressure moves through the area. Winds will veer from north to
east.

Specifics for KSTL: Dry and VFR conditions are expected through
the TAF period with light winds.

Britt

&&

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

$$

WFO LSX



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