Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 252049
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
349 PM CDT Sat Apr 25 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 324 PM CDT Sat Apr 25 2015

The severe weather threat has failed to materialize thus far due
to what appears to be a lack of robust buoyancy owing to marginal
boundary layer moisture and heating. There is a narrow window and
zone with some limited potential for the next few hours, roughly
immediately south of St. Louis and east of Farmington through
extreme southwest Illinois where the lead surface low and
convergence zone is located. This zone will also close quickly as
the lead low migrates e/se and winds shift to the north and west
behind the low. Showers and some isolated thunder will linger into
the early evening from St. Louis south/east but as alluded to the
severe threat should be over by 23z. High pressure and cooler air
will settle into the region for the remainder of the night with
north-northeast winds. Any precipitation beyond the ongoing should
be isolated-patchy in nature. It appears some clearing of the
stratus will commence across northeast Missouri and west central
IL after 09z as northeast winds advect drier air into the area.

Glass

.LONG TERM:  (Sunday through Next Saturday)
Issued at 343 PM CDT Sat Apr 25 2015

High pressure will continue to build into the area on Sunday with
north-northeast low level flow. This flow will lead to continued
southwestward clearing of the stratus while cirrus gradually thins
from north to south as well. Present indications are that there
will be a decent amount of afternoon sunshine and this should
allow temperatures to rise into the 60s, resulting in highs a tad
below average for late April.

Deepening of the northeast U.S. vortex and accompanying
positively tilted upper trof will keep a northerly component to
the flow aloft through Tuesday. This will also maintain
surface high pressure as it builds southward through the MS
Valley. An upper low and trof which evolves in the southwest U.S.
over the next 24 hours will then migrate into the Southern Plains
on Tuesday and into the lower MS Valley Tuesday afternoon-night.
The southern track of this upper system along with dry lower
tropospheric east-northeast flow should keep precipitation at bay
to the south of the region, with predominately high clouds Monday
through early Wednesday.

A tranquil and dry pattern will dominate mid week into early next
weekend. The flow aloft will be rather amplified initially with
the trof axis to our east and surface high pressure maintained
into the later part of the week. By the weekend it appears we
should see ridging aloft move into the Nation`s midsection and a
return to southerly low level flow, bringing above normal temps
well into the 70s and pushing 80 in some locations.

Glass

&&

.AVIATION:  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1253 PM CDT Sat Apr 25 2015

Quick aviation update as storms are developing on radar attm.
Generally expect coverage in rain and IFR to increase and move
south across the area this afternoon into tonight. Strongest
thunderstorm activity expected along and south of the I-70
corridor into early evening. Thunderstorms should taper off into
general showers and IFR ceilings. Rain will end through the mid-
late evening but IFR will persist into Sunday morning.

Carney

&&

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

$$

WFO LSX





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