Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 161158

658 AM CDT Thu Apr 16 2015

.SHORT TERM:  (Today and Tonight)
Issued at 331 AM CDT Thu Apr 16 2015

Shortwave ridging will develop and amplify aloft today and tonight,
providing the area with warmer and drier weather than the past few
days.  Forecast soundings show us mixing up to around 900mb this
afternoon, so used a healthy dose of mix-down temperatures for highs
today, blended with MOS guidance.  This yielded highs at or just
slightly above warmest MOS guidance.  With ridging holding in
tonight, don`t expect much if any precip...although some of the
high-res WRF members do spit out some sprinkles.  Again...this seems
unlikely given the subsidence provided by the ridge aloft.  As a
result, stuck with a dry forecast for tonight.  It looks like
mid-high clouds may be increasing toward morning, and therefore some
decent insulation so I used a blend of guidance which ended up
producing lows close to the warmer end of MOS numbers across the


.LONG TERM:  (Tonight through Wednesday)
Issued at 419 AM CDT Thu Apr 16 2015

Models continue to slow the advancement of the Four Corners low out
into the Great Plains as the week draws to a close.  With the upper
level ridge locked in ahead of the low, it looks like Friday and
most of Friday night should be dry across the CWFA.  Kept some low
chance/slight chance PoPs across parts of central and southeast
Missouri, primarily after midnight as the upper ridge begins to
shift east and the low level jet picks up a bit in response to the
approaching low.  Should see a general increase in shower and
thunderstorm activity through Saturday afternoon into Saturday
evening.  Temperatures Friday and Saturday should stay above normal,
with Friday topping out in the mid to upper 70s.  Saturday looks a
bit cooler due to increasing clouds and shower activity.

The surface reflection of the wave is now forecast to move through
Sunday afternoon/evening with another round of showers and
thunderstorms.  SPC has us outlooked in a 15% probability for severe
weather in their DY4 forecast.  GFS forecasts 1000-1500 J/kg MLCAPE
and 30-40kts of 0-6km shear at 18Z some threat for
severe storms isn`t unreasonable.  However, this forecast is still
far from clear cut with timing uncertainties and the strength of the
upper system as it opens up and is absorbed into the next system
diving in from the north.  Regardless, Sunday still looks a bit
cooler, though with temperatures still near normal, and wet as the
system moves through.

Should see a cool start to the week as another deep cutoff low moves
slowly along the U.S./Canadian border.  This will open the door for
cool Canadian air to filter down through the Plains into the
Midwest.  Below normal highs in the low to mid 60s look reasonable
with lows generally in the 40s.  Don`t see much chance for
precipitation until Wednesday when low level flow turns to the
south-southwest in response to a shortwave moving across the area on
the southern periphery of the larger low to our north.  Resulting
warm advection and moisture convergence could set off some scattered



.AVIATION:  (For the 12z TAFs through 12z Friday Morning)
Issued at 655 AM CDT Thu Apr 16 2015

Broad area of ST with over southern MO is working northeast.
Leading edge of cloud deck...which stretches from N of KCOU to
just NE of UUV...has cigs 1-2kft, but expect these cigs to
increase to above 3kft by the time they arrive at KUIN. Meanwhile,
IFR ST and fog that developed over s IL has expanded wwd into
KSTL. It appears that the wwd expansion of this IFR has slowed
so not certain these IFR conditions will reach KSUS.  Diurnal
heating will cause both these cloud decks to lift during the
morning, and have most locations with VFR ceilings by 17z, with
just a few CU/ST lingering by early evening.

Specifics for KSTL: With KSTL fairly close to the western edge of
the LIFR conditions, expect a fairly quick increase to MVFR cigs
by 15z, with further improvement to low-end VFR cigs by 17z with
this SC/CU deck scattering out during the afternoon.



Saint Louis     75  59  78  60 /  10   5  10  10
Quincy          72  54  76  56 /  10   5  10  10
Columbia        74  57  78  59 /  10   5  10  30
Jefferson City  75  57  77  59 /  10   5  10  30
Salem           72  56  76  56 /  20   5  10  10
Farmington      73  54  76  57 /  10  10  10  10




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