Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 271155

Area Forecast Discussion
National Weather Service Saint Louis MO
655 AM CDT SAT AUG 27 2016

.SHORT TERM...  (Through Late This Afternoon)
Issued at 353 AM CDT Sat Aug 27 2016

SW upper flow remains in place with a short wave lifting NE from
the nthrn Plains into sthrn Canada. Focus remains on trying to
determine convective trends....though this attempt appears to be
futile. Needless to say the location of highest PoPs is low
confidence. The stalled bndry has finally begun to lift back north
over the past several hours and appears to be aligned roughly
along the IA/MO border and on E across cntrl IL as of early Sat
mrng. A weak area of low pressure moving NE will help lift the
front well N of the CWA by this aftn. This will allow the
warm...humid and unstable airmass confined to sthrn IL and sthrn
MO over the past several days to expand across the entire FA. The
lack of a focusing mechanism means that convection may dvlp just
about anywhere at anytime...but should be concentrated temporally
drng the PM hrs.

SPC has the nthrn portion of the CWA in a marginal risk again today.
This is supported by 1000-3000 J/kg of SBCAPE and around 30 kts of
0-6 km bulk shear. Can`t rule out a strong to potentially SVR
storm but modest lapse rates and a moist profile should limit the
SVR threat. The heavy rain threat may be a bigger factor once
again due to PWATs remaining near 2 inches...esp if convection is
able to train over areas that have had recent heavy rainfall.

There is still expected to be plenty of cloud cover today which will
help keep temps in check...holding in the 80s.


.LONG TERM...  (Tonight through Friday)
Issued at 353 AM CDT Sat Aug 27 2016

Tonight through Sunday night

500mb pattern is expected to transition from SW flow to zonal with
best flow along the US/Canadian border. The same airmass will be in
place so expect isld/scttrd diurnal convection. It will not be a
wash out but there will be spotty SHRAs/TSTMs around the area.

Temps will remain near average in the mid/upper 80s with lows near

Monday through Friday

Upper flow amplifies next week with a ridge building across the
cntrl CONUS...though not quite as robust as yesterday. The region
will be on the front side of the ridge which will put the FA on the
fringe of NW flow. Guidance is beginning to change solutions for
next week and is now indicating a cold front may drop into the CWA
Tue. If this occurs...temps will trend cooler towards the end of the
week with a lowering PoP trend as well. Not sold on this new
solution just yet. Unfortunately...the mandated model blend that
loads the extended grids incorporated this solution but...would
prefer to hold off advertising this scenario until guidance shows
some continuity. Regardless of what happens mid-week and
beyond...Mon and Tue should remain quite humid with Dps in the
low/mid 70s and highs near seasonal norms in the mid/upper 80s to
near 90. Isld/scttrd diurnal convection will continue as well...with
better coverage on Tue if FROPA occurs.



.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 634 AM CDT Sat Aug 27 2016

A warm, moist, and unstable atmosphere will spread northward into
the region today. Diurnally-driven showers and thunderstorms are
possible during the afternoon and early evening hours. Winds will
vary between lgt/var and southerly to southwesterly with speeds
AOB 10 kts.





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