Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 210421
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1121 PM CDT Sun Apr 20 2014
Issued at 800 PM CDT Sun Apr 20 2014
Large mid/upper level low/vorticity maxima centered across western
KS/OK will slowly move east across the Central Plains tonight and
phase with the northern stream on Monday across the Midwest. The
northern stream will be responsible for bringing a weak cold front
currently across the northern Plains southeast into the northern
reaches of our CWA by early Monday afternoon.
Currently the greatest coverage of convection is located near the
TX/OK panhandle region where the strongest vorticity advection and
surface convergence was observed. Elsewhere, coverage is isolated
to scattered at best.
Believe that showers and thunderstorm coverage will be slow to
increase from west to east across the area late tonight/Monday
morning. Greatest chances and coverage to occur in the afternoon
and early evening along the advancing cold front where low level
convergence will serve as the focus. Further south diurnal
instability will lead to isolated/scattered coverage, similar to
what is occurring to our west today.
Have increased temperatures from the St. Louis Metro and points
northeast where dry time in the morning and early afternoon should
allow temperatures to rise into the upper 70s despite increasing
.SHORT TERM: (Through Monday)
Issued at 312 PM CDT Sun Apr 20 2014
Models continue to be a bit slower with onset of precipitation
tonight. Will not see showers and a few thunderstorms til after
midnight over central Missouri then slowly increase in coverage from
west to east Monday morning. Surface based capes continue to be on
the increase on Monday, between 500-1200 J/kg, so thunderstorms
possible, though not expecting any severe weather at this time.
Otherwise, mild conditions to persist with lows only in the mid to
upper 50s tonight and highs on Monday will be in the low to mid 70s.
.LONG TERM: (Monday Night through Next Sunday)
Issued at 312 PM CDT Sun Apr 20 2014
Cold front to slide through exiting forecast area by Monday evening,
though some post frontal precipitation not out of the question, so
have chance pops Monday evening, then precipitation comes to an end.
Not a lot of caa behind this system, so lows will be in the mid 40s
to mid 50s Monday night.
Surface ridge to build into region on Tuesday with dry and mild
weather through midweek. Highs will be in the mid 60s to low 70s
Tuesday and Wednesday with overnight lows in the 40s Tuesday night.
Next weather system to move into region Wednesday night and persist
through Thursday night. Best chances of showers and thunderstorms
will be during the day on Thursday. Then dry weather to return for
the first half of the weekend before next system moves in Saturday
night and Sunday. As for temperatures through the period, expect
upper 60s to mid 70s Thursday and Friday with highs in the low 60s
to low 70s for Saturday and Sunday.
.AVIATION: (For the 06z TAFs through 06z Monday Night)
Issued at 1112 PM CDT Sun Apr 20 2014
An upper level disturbance will combine with a cold front to bring
a chance of SHRAs/TSTMs to the region tomorrow...esp during the
aftn. The best chances for precip are expected to occur during the
aftn in assoc with max diurnal heating and passage of the cold
front. Conditions worse than currently depicted will be possible
if any convective element directly impacts a terminal. Winds will
remain sthrly overnight and then become wrly/nwrly after FROPA.
Specifics for KSTL:
The best chance for lowered VSBYs due to precip will be during
the aftn in advance of the cold front. Otherwise expect VFR
conditions with winds aob 10-12 kts.