Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 272258
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
558 PM CDT Tue Jul 27 2021

.SHORT TERM...  (Through Late Wednesday Night)
Issued at 200 PM CDT Tue Jul 27 2021

Key Message: HEAT ADVISORY for Wednesday & Thursday

The ridge of high pressure across eastern Missouri is holding back
the inevitable surge of heat and humidity that will invade the CWA
tomorrow from the southwest and intensify Thursday. Most locations
in our CWA still have dewpoints in the middle to upper 60s, while
the air to our south and southwest is thick, with dewpoints in the
middle and upper 70s. MOS guidance came in a few degrees warmer and
latest 2 meter temperature guidance from CAMs is also in line with a
slightly warmer solution for Wednesday and Thursday. Even with some
mixing occurring in the afternoon, heat index readings should top
out around 105 tomorrow and between 105 and 110 on Thursday. Heat
Advisory was expanded earlier today and is in effect for the entire
CWA from noon on Wednesday through Thursday evening.

CVKING

.LONG TERM...  (Thursday through Next Tuesday)
Issued at 200 PM CDT Tue Jul 27 2021

Key Messages:

1) Marginal Risk of Severe Thunderstorms Thursday Evening

2) Rain chances continue to increase this weekend with below normal
temperatures through the middle of next week.

A cold front is still expected to move across the area Thursday
evening through Friday morning bringing a chance of
thunderstorms. SPC has outlooked the area with a Marginal Risk and
given the strong instability and meager wind shear that will be
in place across the CWA, I concur that a low threat of severe
thunderstorms cable of producing severe wind gusts and locally
heavy rainfall should be messaged.

The front essentially stalls across Missouri from near Kansas City
to the Bootheel this weekend and sets the stage for multiple rounds
of showers and thunderstorms Friday night through Sunday morning.
Mesoscale details, including effective boundary location, will
dictate where the heaviest rainfall occurs. The cloud cover and
rainfall should really limit temperatures and the current forecast
has highs only in the 80s Saturday and Sunday!

Pattern in the long range continues to support below normal
temperatures as an unseasonable trof of low pressure digs across the
eastern CONUS, allowing cool Canadian high pressure to settle south
into the Midwest early next week.

CVKING

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 545 PM CDT Tue Jul 27 2021

Surface high pressure ridge extending from Lake Michigan
southwest into eastern Missouri will move slowly southeastward.
Light surface winds tonight will become southwesterly Wednesday
afternoon, albeit still weak. Little if any cloudiness through the
period. Could not rule out a brief period of light fog at SUS and
CPS late tonight/early Wednesday morning.

SPECIFICS FOR KSTL: Surface high pressure ridge extending from
Lake Michigan southwest into eastern Missouri will move slowly
southeastward. Light surface winds tonight will become
south-southwesterly late Wednesday afternoon and early evening,
albeit still weak. Little if any cloudiness through the period.

GKS

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     73  96  76  99 /   0   0   0  10
Quincy          70  93  75  95 /   0   0   0  20
Columbia        71  96  73  97 /   0   0   0   5
Jefferson City  71  97  75  98 /   0   0   0   5
Salem           69  94  73  97 /   0   0   0   5
Farmington      67  95  72  99 /   0   0   0   0

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory from noon Wednesday to 9 PM CDT Thursday 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...Heat Advisory from noon Wednesday to 9 PM CDT Thursday 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-Washington IL.

&&

$$

WFO LSX


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