Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 150825
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
325 AM CDT Sun Oct 15 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 325 AM CDT Sun Oct 15 2017

The cold front is passing through west central Illinois and central
Missouri at this time.  Showers containing moderate to occasionally
heavy rain are moving east ahead of the front and there are a few
lightning flashes embedded in the line of showers.  Expect the line
to continue moving east through the predawn hours with the heaviest
rain likely clearing eastern sections of the CWFA before 12Z.  An
area of stratiform rain behind the line will likely persist along
and just behind the front through 12-15Z this morning...which should
generally be pretty light.  Model consensus has the cold front
exiting our southeastern counties by 12Z and the last of the
precipitation behind the front exiting by 15Z.

There`s a wide area of stratocu extending north into Iowa and
Minnesota behind the cold front.  Given the strong pressure gradient
and resulting cold advection, this area of stratocumulus should
continue to build south-southeast today and will likely blanket the
CWFA through late morning into early afternoon.  Expect clearing
from northwest to southeast with most areas becoming mostly sunny by
19-20Z.  Gusty northwest flow will bring much cooler air to the
region and highs are only expected to hit the low 60s in most
locations...likely not even cracking 60 in northeast Missouri and
west central Illinois.  With a clear sky tonight and a diminishing
wind, we should have excellent radiational cooling conditions.
Guidance is showing lows in the upper 30s to low 40s in most
locations outside the urban heat island of St. Louis.  This looks
reasonable and would make tonight coolest night of the Fall season
so far.  This will likely be just outside the best temperature range
for widespread frost, but wouldn`t be surprised to see some isolated
frost Monday morning in well protected low lying areas.

Carney

.LONG TERM...  (Monday through Saturday)
Issued at 325 AM CDT Sun Oct 15 2017

Northwest flow aloft will begin the work week on Monday and should
persist until 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.  At the surface, the cool Canadian RIDGE of high
pressure will begin overhead and shift into the southeastern CONUS
and linger thru much of the remainder of the week, giving us a
southerly surface flow.  The atmospheric column will begin the
period quite dry and NW flow aloft and a RIDGE axis extending along
the Gulf Coast should only serve to maintain that.  Any upper level
disturbances detected or not will struggle mightily to generate any
clouds or pcpn and dry weather is favored thru at least Friday.

The southerly low-level flow will give us a warming trend with
temperatures already back to above average by Tuesday with 80s
possible in places for the second half of the week.

The models favor an approaching upper TROF and surface cold front
late next weekend and it looks like this will have the first real
potential for our next rain chance just beyond the end of the
forecast period.

TES

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1145 PM CDT Sat Oct 14 2017

Line of showers and a few thunderstorms will move through the
terminals early in the TAF period. Then MVFR conditions are
expected through the mid morning hours before ceilings lift to low
VFR. Skies are expected to clear during the afternoon hours as
drier air moves into the area. West to northwest winds are
expected to be gusty through at least afternoon.

SPECIFICS FOR KSTL:

Line of showers and a few thunderstorms will move through the
terminal early in the TAF period. MVFR ceilings can be expected
through at least mid morning before lifting to low MVFR. Skies
will clear during the afternoon hours. West to northwest winds
will be gusty into the evening hours.

Britt

&&

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

$$

WFO LSX



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