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fxus63 klsx 272317 
afdlsx

Area forecast discussion...updated aviation
National Weather Service Saint Louis MO
617 PM CDT Thu Jul 27 2017

Short term... (through late Friday afternoon)
issued at 313 PM CDT Thu Jul 27 2017

Latest GOES-16 imagery showed a mesoscale convective vortex moving southeast near the
Missouri/Arkansas line. A cold front extends from near Champaign to
south of Kansas City and the atmosphere remains unstable ahead of it
despite the cloudiness with MLCAPES between 500-1000 j/kg. Regional
radars are still showing scattered showers and a few thunderstorms
ahead of the front. Expect this trend to continue the next few
hours as the front moves south and eventually through the County Warning Area by mid
evening. The clouds will linger around, at least along and south of
I-70, into Friday morning before drier air finally moves into the
area. Partly to mostly sunny skies are still expected on Friday
with north winds as both the GFS/NAM shows a high moving into the
Great Lakes.

Went above MOS guidance tonight where I expect clouds to linger.
Once the clouds clear tomorrow, should have enough sun and mixing to
850mb to go at or above MOS guidance.

Britt

Long term... (friday night through next thursday)
issued at 313 PM CDT Thu Jul 27 2017

Seasonably cool and less humid weather is expected Friday night
through early next week. Mid/upper level ridge is expected to move
westward from the Central Plains to the Great Basin by early next
week with a downstream trough carving out along the eastern Seaboard
of the Continental U.S.. at lower levels, anomalously strong anticyclone will
remain nearly stationary across the upper Midwest to Great Lakes,
helping to provide cool, dry northeasterly flow across the bi-state
area. This area of high pressure will slowly slide east-southeast toward the
Ohio Valley and weaken by midweek. Some agreement on some kind of
cold frontal passage mid-late next week, but differences in timing.
This front is expected to bring the next chance of precipitation to
the area.

Coolest conditions in the extended will likely be this weekend with
850-hpa temperatures only in the +10 to +15c range. Highs on
Saturday and Sunday are forecast only to be in the low to mid 80s,
with lows Sunday morning ranging from the mid 50s to near 60
degrees.

Gosselin

&&

Aviation... (for the 00z tafs through 00z Friday evening)
issued at 614 PM CDT Thu Jul 27 2017

Challenging forecast tonight due to lingering MVFR cigs and the
potential for additional MVFR cigs to develop overnight. Surface
cold front has pushed to near the St. Louis Metro area. As it
moves through, winds will shift to the north-northwest. A few showers will
continue to remain possible near this front for the next few
hours, before all sites go dry overnight. However, low-level dry
air will be slow to move in behind the front, thus some additional
low cigs are expected to develop along and just north of the
front. It will be a close call as to how far north these clouds
will redevelop (likely near the I-70 corridor), but will continue
to remain pessimistic in the St. Louis sites keeping MVFR cigs in
overnight into the morning hours. If the drier air works in a bit
sooner, it is possible these MVFR cigs could be shunted off to
the south. Low cigs should mix out by mid-morning Friday, leaving
VFR conditions with continued northerly winds.

Specifics for kstl:
challenging forecast tonight due to lingering MVFR cigs and the
potential for additional MVFR cigs to develop overnight. Surface
cold front is currently pushing through stl. As it moves through,
winds will shift to the north-northwest. A few showers will continue to remain
possible near this front for the next few hours, before things dry
out tonight. However, low-level dry air will be slow to move in
behind the front, thus some additional low cigs are expected to
develop along and just north of the front. It will be a close call
as to how far north these clouds will redevelop (likely near the
I-70 corridor), but will continue to remain pessimistic at stl
keeping MVFR cigs in overnight into the morning hours. If the
drier air works in a bit sooner, it is possible these MVFR cigs
could be shunted off to the south. Low cigs should mix out by mid-
morning Friday, leaving VFR conditions with continued northerly
winds.

Kd

&&

Lsx watches/warnings/advisories...
MO...none.
Illinois...none.
&&

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