Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 031755

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1255 PM CDT TUE MAY 3 2016

Issued at 1147 AM CDT Tue May 3 2016

Forecast on track with only minor adjustments made.

Vort max moving thru central and southeast MO and southern IL this
afternoon will act upon a diurnal CU field that would otherwise
already form and result in isolated to scattered SHRA mainly for
areas in STL metro, southeast MO, and far southern IL, with this
activity diminishing or exiting by sunset. Boosted PoPs into
chance category in some areas.

Max temps still look to be in the 60s, with coolest values
underneath the thickest clouds and better rain chances in
southeast MO.

Next chance of rain with a cold front dropping down late tonight
looks wetter than before, and have boosted PoPs to higher-end
chance and even some likelys for areas mainly east of the MS
river after midnight. This should be nearly out of our area by
sunrise Wednesday, perhaps lingering in southern MO and far
southeast MO. Min temps will be in the 40s in southeast MO where
clear skies can last the longest, and 50s in the north.



.SHORT TERM...  (Through Late This Afternoon)
Issued at 405 AM CDT Tue May 3 2016

In the short term, concern will be duration of fog that has
developed over portions of central MO. Cloud cover and slightly
drier air advecting into that region is complicating the forecast
and increasing the uncertainty as to how long any fog will persist.
Will go with a Dense Fog Adv thru about 13z for portions of central
MO and address changes as needed.

Otherwise, main concern today will be cloud cover, and therefore,
also temps today.

Mdls are in fairly good agreement with phasing of the upper trof and
pushing swd thru the area today. This shud be just enuf support to
generate isod SHRA again this afternoon. However, do not believe
that coverage will be as great as yesterday and shud be confined to
the srn third or so of the CWA. This same area will see much more
cloud cover than the remainder of the area.  Have therefore trended
aob the cooler guidance for today in these areas. Elsewhere, trended
twd a compromise.


.LONG TERM...  (Tonight through Monday)
Issued at 405 AM CDT Tue May 3 2016

While upper level shortwave exits forecast area, secondary cold
front to approach region this evening. Will see activity continue to
fire up along the boundary, moving into northern portions of forecast
area by 04z Wednesday. Some decent instability, so would not be
surprised to see showers with some isolated thunderstorms as
activity sinks south tonight. Best chances will be along and east
of Mississippi River. Otherwise, it will be a bit milder with lows
in the mid 40s to low 50s.

On Wednesday, cold front to exit forecast area with some lingering
precipitation over eastern portions of forecast area. With northerly
flow over region, will see highs in the mid 60s to low 70s, just a
bit below normal.

Region dries out for remainder of work week as surface ridge builds
in. Temperatures to moderate, warming back up into the mid to upper
70s on Friday, then into the upper 70s to low 80s on Saturday.

No major changes to forecast for last half of weekend as next system
moves into the region. Showers and thunderstorms will be on the
increase Saturday night and persist through Monday.



.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1255 PM CDT Tue May 3 2016

VFR conditions will prevail at the TAF sites thru the valid
period. Two periods of rain chances: this afternoon should stay to
the south of the TAF sites, with STL metro on the far northern
edge and the second associated with a cold front should be a
better chance for sites near the MS river and east. May need to
upgrade this to a TEMPO later on. Otherwise, look for surface
winds to shift from NW to SW by this evening ahead of the front
and then veer from the NW again with gusts on cold FROPA late





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