Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 161201

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
701 AM CDT Mon Oct 16 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 330 AM CDT Mon Oct 16 2017

High pressure centered over northern Texas will move northeast
across the Mississippi Valley into the Mid Atlantic Region by early
Tuesday morning.  The high will bring our area tranquil weather and
temperatures near seasonal normals in the mid 60s today.  Should see
temperatures a few degrees warmer in the mid 40s over northern
portions of the forecast area tonight as light southerly flow
develops northwest of the ridge axis.  Temperatures will be
cooler in the upper 30s to around 40 under the ridge axis
across southeast Missouri.


.LONG TERM...  (Tuesday through Sunday)
Issued at 330 AM CDT Mon Oct 16 2017

Northwest flow aloft will continue thru Wednesday, gradually de-
amplifying with time.  A RIDGE aloft is then expected to build over
our region on Thursday and then shift eastward, resulting in a SW
flow aloft heading into next weekend with a TROF approaching on
Sunday.  At the surface, a southerly flow will prevail for much of
this period, with a weak cold front edging our region to the north
Wednesday night and early Thursday.  A more meaningful cold frontal
passage looks slated for Sunday.

The atmospheric column will begin the period quite dry thanks to NW
flow aloft and a RIDGE axis extending along the Gulf Coast
effectively choking off any moisture return.  Any upper level
disturbances set to slide thru will struggle mightily to generate
any clouds or pcpn and dry weather is favored thru at least Friday.

The southerly low-level flow during this period will result in
temperatures above average thru the period with some 80s possible in
places for Friday and Saturday.

The models continue to signal support to the breakdown in the dry
stranglehold on our weather by Saturday, with flow from the Gulf of
Mexico opening up and flow aloft having gone SW some time earlier.
With weak upper level disturbances anticipated to stream into our
region on Saturday ahead of the approaching upper TROF, have
mentionable PoPs beginning on Saturday afternoon and then trend them
into likely category with a much stronger signal with cold frontal
passage on Sunday.



.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 643 AM CDT Mon Oct 16 2017

VFR flight conditions are expected to prevail across the area
today. Visibility will be reduced locally this morning due to
steam fog in the vicinity of area rivers. The steam fog will
dissipate by 13-14Z. Light wind will turn to the south across the
area tonight as the surface ridge drifts east of the region.


VFR flight conditions will prevail at Lambert through Tuesday
morning. Expect light and variable wind to become southerly this
evening as a surface ridge moves east of the area.





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