000
FXUS63 KLSX 181044
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
544 AM CDT Wed Oct 18 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 336 AM CDT Wed Oct 18 2017

Early this morning, a RIDGE of surface high pressure extended from
the Mid-Atlantic states, thru the mid-South, and back into eastern
Texas, resulting in a light southerly flow for our region. Northwest
flow prevailed aloft, with another upstream upper level disturbance
over southeastern Nebraska.  The atmospheric column remains bone
dry, and the disturbance is once again only able to generate an area
of high cirrus clouds out ahead of it.  Temperatures range from the
mid to upper 30s in sheltered areas in the eastern Ozarks of
southeast Missouri to the lower 50s in the prairie regions of
northeast Missouri with a lot of 40s in between.

The surface RIDGE axis of high pressure will remain nearly
stationary to our south but will weaken in strength some over the
next 24 hours.  A weak surface cold front will approach our region
this evening but only make it as far as southern and eastern Iowa
before stalling out.  The result will be another day of southerly
flow but a tad stronger than yesterday with a tighter pressure
gradient from the approaching front.  The only clouds expected will
be a region of somewhat thin cirrus clouds from the upper level
disturbance that will move thru mainly this afternoon and evening.
The column will simply be too dry for any pcpn to develop.

Thanks to continued southerly flow, the warming trend will continue
with max temps in the low to mid 70s expected.  Likewise, min temps
tonight will be a bit higher than persistence with mid 40s to lower
50s expected for most areas.

TES

.LONG TERM...  (Thursday through Tuesday)
Issued at 336 AM CDT Wed Oct 18 2017

High pressure centered over the central Appalachian Mountains at
the beginning of the period will remain nearly stationary through
Friday night. Meanwhile, the ridge aloft will amplify over the
Mississippi Valley Thursday and Friday as a strong trof digs into
the western U.S. Thursday and Friday still look warm with
southerly flow on the western side of the high and the increasing
heights aloft as the ridge amplifies; therefore have tweaked
temperatures up Thursday, Friday, and Saturday a few degrees over
ensemble guidance

The trof will continue moving east into the Great Plains Saturday,
forcing a cold front ahead of it into the Mississippi Valley. Models
continue to be in good agreement through Friday, and have come into
better agreement on the speed of the trof as it moves through the
Great Plains on Saturday.  However...the GFS now develops a cut off
low over Texas late Sunday night while the ECMWF is progressive with
the trof.  This is a reverse from a few days ago when the ECMWF was
the model with the cut off low over the Gulf Coast.  All guidance
points to a FROPA on Sunday, but am leaning toward the ECMWF`s open
wave solution and dry weather after the FROPA.  This would be more
consistent with the previous forecast...and previous runs of the
models.  Medium range models do become a little more consistent by
the end of the forecast on Tuesday with a longwave trof over the
eastern 1/2 of the U.S. and northwest flow at all levels over the
Mississippi Valley.  This is a cool pattern which should bring
temperatures back to near normal.

Carney

&&

.AVIATION...  (For the 12z TAFs through 12z Thursday Morning)
Issued at 544 AM CDT Wed Oct 18 2017

VFR conditions, dry weather, and southerly surface winds will
prevail at the TAF sites thru the valid period. Wind speeds may
top 10kts at times during late morning and afternoon.

TES

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX