Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 161128

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
628 AM CDT Thu Mar 16 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 350 AM CDT Thu Mar 16 2017

Focus for today will be temps, then switching to PoPs tonight.

Mdls remain in fairly good agreement thru tonight. However, there
are some small differences in available low level moisture today.
The GFS, and to a lesser degree the ECMWF, suggest the strong WAA
associated with the wrmfnt today will generate an area of light
SHRA. However, the NAM/RAP/local WRF and the numerous CAMs, keep any
precip north of the CWA with less available moisture this far south.
Seems this setup is more difficult to get measuring precip when RA
is the suggested p-type. Have therefore lowered PoPs below slight
chance, but kept a chance for sprinkles mentioned.

With the continued WAA and strong moisture return over the region
this evening, mdls are printing out a fair amount of QPF. With the
cloud deck suggested to be only 3 kft thick, do not believe that the
area will see much in the way of precip tonight. There are a couple
of caveats, however. First, precip may turn out to be more of a DZ
event over the srn portions of the area. This seems less likely due
to progd winds. Mdls prog a s/w dropping sewd across IA into IL
tonight. Believe this will remain north of the CWA and keep any
precip out of the area, however, have kept some chance PoPs due to
uncertainty in the track of the s/w.

As for temps today, with strong WAA expected, have trended aoa the
warmer guidance despite expected cloud cover. For tonight, with sly
to sely winds continuing thru the night and extensive cloud cover,
temps will have a hard time dropping. However, there may be a brief
time early in the evening where breaks in clouds allow temps to drop
quickly when less mixing is expected. That said, the going forecast
may be too cold.


.LONG TERM...  (Friday through Wednesday)
Issued at 350 AM CDT Thu Mar 16 2017

Cold front to move southeast through forecast area on Friday,
exiting by Friday evening. Increasing low level moisture and some
decent instability just ahead of front so in addition to showers
developing, isolated thunderstorms not out of the question through
early Friday evening. As for highs on Friday, will depend on timing
of frontal boundary, cloud cover and precipitation. For now have
highs in the upper 50s to upper 60s.

Weak surface ridge to build in on Saturday, but shift to our east by
Sunday. So a short period of dry weather before some WAA showers
develop Sunday morning as warm front lifts northward through region.
Highs will be a bit cooler on Saturday, in the low 50s to low 60s,
but moderate some on Sunday with highs in the mid 50s to upper 60s.

Better chances of showers and storms beginning Sunday night with
decent MUCAPES, low level moisture and convergence along a strong
cold front. The precipitation will be on the increase with best
chances late Sunday night through Monday evening, before tapering
off early Tuesday. Monday will be the warmest day this week with
highs in the mid 60s to low 70s. Highs to dip down to near normal
for the middle of the work week.



.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 621 AM CDT Thu Mar 16 2017

High clouds will continue to move ewd this morning with cigs
actually lifting later this morning and into the afternoon. Cigs
will lower again late this afternoon into the evening hours
eventually reaching MVFR. Winds will veer throughout the period
with gusts this afternoon and early evening. Have added LLWS for
late in the period when sfc winds diminish somewhat. The LLWS is
somewhat borderline and will depend on the LLJ and if sfc winds
diminish. Chances for precip are too low attm to mention in TAF.



MO...Freeze Warning until 10 AM CDT this morning for Audrain MO-Boone
     MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
     Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln MO-Madison MO-
     Marion MO-Moniteau MO-Monroe MO-Montgomery MO-Osage MO-Pike
     MO-Ralls MO-Reynolds MO-Saint Charles MO-Saint Francois MO-
     Saint Louis City MO-Saint Louis MO-Sainte Genevieve MO-
     Shelby MO-Warren MO-Washington MO.

IL...Freeze Warning until 10 AM CDT this morning for Adams IL-Bond IL-
     Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-Jersey
     IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-Montgomery IL-
     Pike IL-Randolph IL-Saint Clair IL-Washington IL.



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