Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 260501

1201 AM CDT Tue May 26 2015

Issued at 927 PM CDT Mon May 25 2015

An extensive MCS which originated this afternoon across the
southern Plains continues to push eastward into the lower MS
Valley this evening. Large scale ascent associated with the
upstream shortwave trof, ponounced southerly lower trop flow of
moist unstable air, and system relative convergence is helping
maintain the line from AR into Eastern TX, however radar has begun
to show decreasing convective organization on the northern periphery
which is moving more northeastward into MO. This may result in a
diminished severe threat for southern MO. However, the southerly
LLJ is forecast to ramp up and veer later tonight and this combined
with large scale ascent associated with the progressive shortwave
trof and an apparent newd moving MCV presently in NW AR should
maintain a shield of northeast moving showers and thunderstorms.



.SHORT TERM: (Tonight through Thursday)
Issued at 236 PM CDT Mon May 25 2015

Expect quiet weather to continue for any remaining holiday
festivities this evening, with the anticipation that the northern
portion of the aforementioned MCS, likely in a decaying phase,
will be entering our southwestern counties shortly after midnight.
Large scale ascent with the shortwave should initiate additional
convection further north as well with the entire area moving
northeast through the remainder of the CWA through daybreak on
Tuesday. Not sure how much redevelopment will be able to occur
Tuesday afternoon in the wake of the morning rain. Have lowered
PoPs from west to east Tuesday afternoon.

Have chance PoPs continuing Tuesday night through Thursday as a
series of weaker shortwaves are forecast to impact the area as the
upper level pattern temporarily becomes a little more zonal.


.LONG TERM: (Next Weekend)
Issued at 236 PM CDT Mon May 25 2015

Thunderstorm chances will steadily increase as the upper trough will
deepen again to our west by the end of the work week and actually
progress east into the middle Mississippi River Valley by the end of
the weekend. Temperatures will remain near normal for the end of May.



.AVIATION:  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1143 PM CDT Mon May 25 2015

Primary concern continues to be the area of rain and thunderstorms
moving northeast through southern Missouri at this time. While the
storms have weakened substantially since 00Z, it does look like
they will roll up along the I-44 corridor through 09Z. Trailing
rain will likely affect areas along and south of I-70 through
sunrise. Some marginal ceilings have developed ahead of the rain
as well, with heights around 2,000 ft. Unsure how the storms will
affect ceilings...they may mix out or reinforce and possibly
lower them. Am leaning toward the former as ceilings back over
southern Missouri are mostly VFR. Thunderstorms will likely
produce brief visibility at or below 3SM in moderate rain. A few
showers and possibly some isolated thunderstorms remain likely
further north as the upper level system associated with the storms
continues to move northeast. Expect VFR flight conditions to
prevail north of the I-70 corridor. VFR conditions are expected to
prevail on Tuesday with gusty south-southwest wind. There is a
chance for more storms in the afternoon...mainly east of the
Mississippi and across portions of northern Missouri.

Specifics for KSTL:

Expect the line of broken storms moving northeast across the
Ozarks to reach the terminal just after 08Z. Some gusty winds and
brief MVFR flight conditions are likely as the line passes. Unsure
if the storms will bring lingering MVFR ceilings or wash the
ceilings out, but am leaning toward the former as ceilings across
southern Missouri behind the line are mainly VFR. VFR conditions
are expected to prevail on Tuesday with gusty south-southwest
wind. There is a chance for more storms in the afternoon...mainly
east of the Mississippi.





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