Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 260001
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
701 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.
.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.
.AVIATION: (For the 00z TAFs through 00z Sunday Evening)
Issued at 636 PM CDT Sat Apr 25 2015
There is a substantial band of IFR/MVFR CIGS that stretch from
KS/NE thru MO and IL and points east into KY/OH. Existing IFR CIGs
are expected to last most...if not all night. A dry NE low level
flow in the wake of today`s storm system will help dry the lower
levels out and push the band of IFR/MVFR CIGs south Sunday mrng.
Current indications are that the CIGS should push out of all the
terminals...from N to S...in the 10-15Z time frame. Diurnal
cu/strato cu is expected to dvlp drng the mrng but should thin out
some drng the aftn. VFR conditions are fcst for the aftn at all
Specifics for KSTL:
Terminals should be socked in with IFR CIGs all night long.
Stratus should eroded from the NE tomorrow mrng 12-15Z with low
end VFR diurnal cu/strato cu filling in behind the clearing. This
too should dsspt by evng leaving a VFR fcst overnight with a N/NE
breeze aob 10kts.