Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 061139

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
639 AM CDT FRI MAY 6 2016

.SHORT TERM...  (Through Late This Afternoon)
Issued at 314 AM CDT Fri May 6 2016

High pressure centered over northern Arkansas will drift southeast
today.  Light west-southwest flow will increase in response to the
passing ridge axis today...particularly over western portions of the
CWFA.  850mb temperatures will be on the increase as well with
readings increasing from the single digits into the teens today.
Forecast soundings show some fairly deep used a
combination of ensemble MOS and mix-down temperatures for highs this
afternoon.  This yielded max temperatures close to or a bit higher
than operational guidance.  Overall, high temperatures should be
around 10 degrees higher today than Thursday.  Other than that,
it should be another tranquil day.


.LONG TERM...  (Tonight through Thursday)
Issued at 314 AM CDT Fri May 6 2016

GFS/NAM/ECMWF are in good agreement that upper ridge that will be
over the plains tonight will not move east of the area until Monday
morning.  However, models are still consistent a cold front will
drop south out of Iowa and northern Illinois by late Saturday and
Saturday evening before it stalls over the central part of the CWA
Saturday night and early Sunday.  Still looks like this front will
be a focus for scattered thunderstorm development on Saturday
afternoon and evening.  Also can not rule out the potential for a
few strong thunderstorms on Saturday as MLCAPES will be in the 1000-
2000 J/kg range and 0-6km shear will be around 40kts which favors
organized convection.

Additional scattered storms are expected on Sunday as the front
moves back north during the afternoon and early evening as the front
moves back north as a warm front.  Will keep likely PoPs on Sunday
night as we get into southwesterly upper flow and decent low level
jet kicks in allowing for strong low level moisture convergence over
the area.  Will continue to see the threat for showers and
thunderstorms into Monday and Tuesday as strong low level forcing
will continue under a series of mid level troughs moving out of the
Great Plains.

The threat for severe weather will be dependent on how unstable the
airmass will be at any one time, particularly if the atmosphere can
recover from a previous round of convection.  GFS and ECMWF do not
show that attendant cold front will move across the area until
Tuesday night or Wednesday, so will keep showers and thunderstorm in
the forecast through midweek.   By Thursday, drier weather is
expected as the GFS and ECWMF show the upper low moving off to the
east and a surface high moving into the area.

Temperatures are expected to be at or above normal through the
period.  Highs tomorrow will be above normal as 850mb temperatures
climb to around +15C.



.AVIATION...  (For the 12z TAFs through 12z Saturday Morning)
Issued at 635 AM CDT Fri May 6 2016

High pressure over northern Arkansas will continue to bring dry
and tranquil weather to the area through Saturday morning. VFR
flight conditions are expected to prevail. There is a chance there
could be some low level wind shear late tonight...primarily across
northern Missouri and west central Illinois. Confidence is low at
this time so have not mentioned in the TAFs yet.

Specifics for KSTL:

VFR flight conditions are expected to continue to prevail at
Lambert through Saturday morning.





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