Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 240754

Area Forecast Discussion
National Weather Service Saint Louis MO
254 AM CDT Mon Apr 24 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 254 AM CDT Mon Apr 24 2017

Ridge axis extending from west central Illinois through central into
southwest Missouri will drift eastward today.  Wind will turn to the
south-southeast after the ridge axis pases and Warm advection will
allow temperatures to rise above yesterday`s highs.  850mb temps
between 12 and 14 degrees mix down to mid 70s to around 80 this
afternoon. This looks reasonable given the warm April sunshine and
yesterday`s temperatures in the low to mid 70s so stuck pretty close
to warm MAV guidance today.  Southerly flow will continue tonight
which should continue the warming trend.  Overnight lows MOS
guidance lows in the upper 40s to low 50s look reasonable with
slightly warmer temperatures in the urban areas of St. Louis.


.LONG TERM...  (Tuesday through Sunday)
Issued at 254 AM CDT Mon Apr 24 2017

Still looks like it will be an active weather week for showers and
thunderstorms through next weekend with the potential for a few
strong to severe thunderstorms and the potential for an additional 2-
5+ inches of rainfall by Sunday.

Upper trough entering the Pacific northwest today will deepen over
central Plains by Wednesday.  We will still see low level flow turn
out of the south ahead of it on Tuesday with 850mb temperatures
climbing to around 15C.  Highs near 80F still look good tomorrow
afternoon.  The chance for showers and thunderstorms will increase
late Tuesday night into Wednesday as both the GFS/ECMWF are showing
strong low level convergence developing along and ahead of the cold
front beneath strong mid-upper ascent ahead of the upper trough.
Could be a few strong or severe thunderstorms ahead of the cold
front given MLCAPEs of 1000-2000 J/kg and deep layer shear around
50+kts. Heavy rainfall will also be possible given PWATS over 1.5
inches and the potential for training cells.

Rain chances will continue into Wednesday night and early Thursday
as the upper trough will not exit the area until midday.  After a
brief break in the rain chances late week as a weak shortwave ridge
moves across the area, showers and thunderstorms will return by
Friday night.  This is when the GFS/ECMWF shows the front returning
back north as a warm front.  There should be a strong low level
moisture convergence on the nose of 40kt low level jet which will
produce showers and thunderstorms Friday night into Saturday.  The
warm front will move slowly north into the CWA on Saturday and
Saturday night as the upper low over the southwestern CONUS moves
east into the Plains.  A surface low will move northeast out of the
Plains on Saturday into the Midwest on Sunday bringing a cold front
across the area on Sunday. Both the GFS/ECMWF are showing sufficient
instability and shear for additional strong thunderstorms.   In
addition, shear vectors will be aligned for training storms with
both the GFS and ECMWF showing the potential for locally heavy
rainfall over the weekend.

After a brief cool down with highs only in the 60s on Thursday with
850mb temperatures only around 5C, temperatures will climb back up
above normal next weekend in the warm sector with 850mb temperatures
around 15C.



.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1202 AM CDT Mon Apr 24 2017

VFR through the period due to the influence of a high pressure
center located across the region. Light/variable winds at TAF
issuance will become prevailing southeasterly by 12z and increase
slightly after 15z.





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