Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 111543
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
1043 AM CDT Fri Apr 11 2014

.UPDATE:
Issued at 1042 AM CDT Fri Apr 11 2014

Stationary front is currently across far southern Missouri into
the southern tip of Illinois. Latest run of the RAP shows some
instability developing along the pooling dewpoints this afternoon
right along the front. Think that this area will be the only
location for any isolated storms to form, so have shifted slight
chances to the far southern counties for this afternoon only.
Otherwise temperatures are warming nicely, even with the clouds
and the east winds, so added a degree or two to the highs. This
current batch of mid-high clouds will continue to move quickly
east and should exit the eastern counties by mid-late afternoon.

Britt

&&

.SHORT TERM:  (Through Late This Afternoon)
Issued at 356 AM CDT Fri Apr 11 2014

A stalled cold front which was located south of the CWA at 05z will
lift slightly northward as a warm front later today. Isolated to
scattered showers/thunderstorms are possible near the front during
the afternoon hours, mainly across the southern part of the CWA
including the eastern Ozarks. Most areas should remain dry today.
Expect highs in the upper 60s to around 70.

Kanofsky

.LONG TERM:  (Tonight through Thursday)
Issued at 356 AM CDT Fri Apr 11 2014

(Saturday-Monday)

Overnight increase of southerly low level flow should allow
frontal boundary to lift back north across the area, placing the
entire CWA in the warm sector no later than midday. MET/MAV MOS is
trying to develop some lower clouds late tonight and then linger
it throughout the day on Saturday, but given what appears to be a
very thin ribbon of stratified low level moisture not certain this
cloudiness will actually develop, and if it does even more dubious
that it would be able to hang around all day. Have gone several
degrees above warmest MOS based on this spring`s trend of guidance
being consistently too cool during warmups, and if there are even
fewer clouds we may need to tack several more degrees onto this.

Saturday night, Sunday, and into Sunday night, attention turns to
increasing thunderstorm chances with strong upper level trof and
associated cold front.  I have introduced a slight chance of storms
as early as Saturday afternoon in our far north for the outside
chance of renegade storms, but it would appear that a much better
chance of storms in our northern and western areas would be later
Saturday night as storms that fire along cold front over IA during
the late afternoon and early evening hours slowly work east.   All
of the 00z guidance is also consistent in suggesting a secondary
area of convection developing over northwest MO along zone of low
level convergence that will also work east during the predawn hours.

Categorical PoPs will overspread the region from NW to SE on Sunday
and Sunday night as cold front and strong trof work their way into
the Mid-Mississippi Valley.  A few severe storms or strong line
segments will be possible with convective initiation along the cold
front during the afternoon and early evening as 00z runs are
suggesting MLCAPES 1500-2000 j/kg during max heating along with
30-50kts of deep layer shear.  In addition, the ample moisture, slow
system movement, intense baroclinicity and strong dynamics (with
some possible coupling between jet cores in the northern and
southern streams) all suggest widespread rains aoa 1" over the
northwest half of the CWA in the Sunday/Sunday night time frame.

Models have come into much better agreement with timing of front
across the region, and by 12z Monday the strong cold front will
extend from the Missouri Bootheel to extreme southern IL, placing
the entire CWA in the much colder air.  This should mean a cold and
blustery Monday, with rain winding down from west to east across the
FA.  Temperatures will be nearly steady in our SE counties due to
the strong CAA and rain, and in the west where the rain will end
early only expecting a 5-10 degree rebound from early morning lows.

(Tuesday-Thursday)

Monday`s chilly weather will continue into Tuesday, and right now it
appears that Tuesday Morning`s lows will be in the 30-35 degree
range. It`s difficult to time surface features this far out, but if
00z guidance is correct winds will be too strong for much in the way
of frost, in spite of these chilly readings.  Highs will be in the
50s.

Region should then experience a warming trend heading into midweek as
upper trof swings into the East Coast and heights rebound across the
Central CONUS, with highs well in the 60s by Thursday.

With dry air and dynamics remaining well to the north and west of
the CWA don`t foresee any rain threat in the Tuesday-Thursday time
frame.

Truett

&&

.AVIATION:  (For the 12z TAFs through 12z Saturday Morning)
Issued at 626 AM CDT Fri Apr 11 2014

VFR for at least the first 6-12 hours and probably longer. Some
MVFR stratus is possible at KCOU/KCPS/KSUS tomorrow morning around
daybreak. Winds remain northeast on the cool side of a stalled
frontal boundary, then become southeast to south once the boundary
lifts north.

Specifics for KSTL: VFR for at least the first 6-12 hours and
probably longer. Some MVFR stratus is possible tomorrow morning
around daybreak. Winds remain northeast on the cool side of a
stalled frontal boundary, then become southeast to south once the
boundary lifts north.

Kanofsky

&&

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

$$

WFO LSX






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