Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 250832
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
332 AM CDT SAT JUN 25 2016

.SHORT TERM...  (Through Late This Afternoon)
Issued at 300 AM CDT Sat Jun 25 2016

Main forecast issue for today is convective trends and probabilities.
As usual with warm season QPF in the absence of significant forcing,
the deterministic models have rather varied solutions. The CAMS
are having issues as well and the hourly HRRRs seem to change with
each new run. A few spotty showers and storms have developed in
central MO on the cool side of a ill-defined warm front drapped
from SW NE across NE KS thru SW MO. These appear to be high-based
and are occuring within a region of weak moisture convergence
associated with a southwesterly LLJ and also ahead of a weak
elongated vort max. My initial thinking is we will continue to see
some of this spotty/scattered activity across central/eastern MO
through early morning and then it will dissipate. By early
afternoon however I am thinking a new round of scattered storms
will develop within the unstable air mass across eastern MO, in
response to the northeastward moving warm front and the meandering
vort max. The storms should continue to develop and shift eastward
through western IL during the afternoon attendant with the east-
northwest advancing warm front, moving out of the CWA by early
evening.

Glass

.LONG TERM...  (Tonight through Friday)
Issued at 300 AM CDT Sat Jun 25 2016

A progressive upper trof will move across the upper MS Valley
tonight and this will help push a cold front southward entering NW
MO by early Sunday morning. Extensive convection is expected to
span the cold front and with the LLJ veering to more westerly ahead
of the front, some of this activity will likely progess into
northeast MO in the early morning hours on Sunday. The cold front
and a pre-frontal trof will continue to advance slowly southward
during the day with heating contributing to an increasingly
unstable and uncapped air mass, and should be the focus for
scattered to numerous showers and thunderstorms by Sunday
afternoon.

On Sunday night and Monday the focus for showers and storms will
shift to southern MO and southern IL as the front sinks southward,
and then as the initial cold front is reinforced by a stronger
cold front on Monday. Cooler and drier air will spread into the
region on Monday night and Tuesday as a formidable surface high
settles southward through the north central U.S. in response to
large scale amplification and an evolving upper trof across
eastern NOAM. This air mass will prevail thru Thursday as high
pressure continues to settle southward resulting in below average
temperatures. The latest guidance is beginning to suggest the
northwest flow short wave track may remain west of the area and
the previously anticipated threat of showers and thunderstorms
late Wednesday and Thursday may instead occur from the central
Plains into southwest MO. This is still 5+ days away so we won`t
be too quick to drop pops based on a single model cycle.

Glass

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1124 PM CDT Fri Jun 24 2016

For the most part dry, VFR conditions to prevail through forecast
period. As warm front lifts northward through region will see
isolated/scattered storms develop Saturday afternoon. Kept VCTS
mention in metro area tafs. Otherwise, light southeast to south
winds to pickup from the south by mid morning.

Specifics for KSTL:
For the most part dry, VFR conditions to prevail through forecast
period. As warm front lifts northward through region will see
isolated/scattered storms develop Saturday afternoon, then
diminish after sunset. Kept VCTS mention in metro area tafs.
Otherwise, light southeast to south winds to pickup from the south
by 15z Saturday.

Byrd

&&

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

$$

WFO LSX



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