Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 212322

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
622 PM CDT SAT MAY 21 2016

.SHORT TERM...  (Tonight through Sunday Night)
Issued at 344 PM CDT Sat May 21 2016

High pressure stretching from the Upper Midwest all the way to the
Gulf Coast will continue to control our weather tonight and Sunday.
Wind will become light and variable by late tonight under a clear
sky.  This should allow for good radiational cooling. Don`t see any
reason we won`t cool down to near dewpoint temperatures in the low
to mid 50s.

Ridge axis will drift east of the CWFA Sunday which will allow weak
warm advection to begin.  Expect this will be the beginning of the
warming trend for the week. Strong insolation along with the weak
warm advection will likely push temperatures up at least into the
low 80s.  Guidance may actually be a little on the cool side so I
bumped up a couple of degrees.  Ridge will continue moving east
Sunday night with low level flow increasing from the south-
southwest.  Lows Sunday night will likely be a bit warmer than
Sunday morning`s lows due to the warmer start to the evening and the
continuing weak warm advection.


.LONG TERM...  (Monday through Next Saturday)
Issued at 344 PM CDT Sat May 21 2016

Broad pattern shift still in the works for next week.
Temperatures will continue to drift upward in a broad area of warm
advection. Low level moisture will also be increasing as the Gulf
of Mexico opens up. Still think we can hold off precip for the
majority of the area on Monday as the real push of higher boundary
layer moisture will be up through the Great Plains into the Upper
Midwest. The reprieve from higher dewpoints will likely come to an
end on Tuesday as the southeast ridge axis finally shifts east far
enough to allow a straight shot from the Gulf into the mid
Mississippi Valley with nothing but the Ozarks to stop it. Deep
southwest flow and a persistent longwave trof over the western
CONUS will keep the warmth and humidity pouring up into our area
through the end of the week. Will have a more or less continuous
30-50% chance for rain from Monday night through the end of the
week. SPC pushed 15% risk for severe into our area for Wednesday
and Thursday. GFS develops some very strong instability as the
boundary layer moisture increases. 0-6km shear is modest Wednesday
at 20-30kts but stronger 40-50kts on Thursday. Either way, think
severe threat is conditional on all that CAPE developing. If we
can realize the instability, it could be a very busy mid-late
week for severe weather.



.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 618 PM CDT Sat May 21 2016

VFR and dry thru the TAF period. A patch of mid level clouds will
push swd this evening as an upper level disturbance moves thru the
region. Otherwise, a sfc ridge will build into the region with
light winds thru the period.





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