Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 222044

Area Forecast Discussion
National Weather Service Saint Louis MO
344 PM CDT Sat Oct 22 2016

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 343 PM CDT Sat Oct 22 2016

High pressure at the SFC and aloft will combine to produce quiet wx
thru the end of the wknd. SFC ridge will remain centered over the
Lower MS Rvr Vly and SE US thru Sun which will keep sthrly flow
going. A short wave is fcst to top the ridge tonight and then pass
to the N/NE of the region tomorrow. An 30-40KT E-W LLJ is expected
to dvlp tonight across MO and into sthrn IL. There is decent WAA and
850 moisture convergence overnight in assoc with this feature but a
very dry atmosphere limits expected cloud cover let alone
mentionable PoPs. The short wave will drag a cold front thru the
area Sun aftn. Due to the bone dry atmosphere...FROPA is expected to
be dry.

Temps tonight should not be as cool as last night since the SFC
ridge axis will have shifted to the SE and winds will remain around
5 kts overnight. High temps tomorrow will also have a chance to
moderate about 5 degrees from today`s high temps due to the
sustained sthrly flow that is expected to become SW/WSW thru the day
and full sunshine. Temps are expected to be some 5-10 degrees above
average thru the remainder of the wknd.


.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 343 PM CDT Sat Oct 22 2016

The effective cold front should be up across northern Missouri
stretching into northwest Illinois.  The front will push south
overnight and should be through the CWFA down to near the
Missouri/Arkansas-Kentucky/Tennessee border by sunrise on Monday.  A
ridge of high pressure stuck over the Gulf Coast will block any
decent moisture return ahead of the front, so the FROPA still looks
dry.  The low level thermal gradient behind the front looks like it
will set up from Columbia northeast across the Mississippi River
with warmest readings out in central and southwest Missouri.  For
most of our CWFA , this should be another little shot of Fall
with temperatures falling back to near or a few degees below normal.
Much of central and southern Missouri will probably remain a few
degrees warmer though.

The surface ridge behind the front will build across the eastern 1/3
of the CONUS and south-southeast flow will prevail through Tuesday
night ahead of the next shortwave.  With the aforementioned thermal
gradient still in place, expect warmest temperatures to continue to
be across central Missouri on Tuesday with highs 3-5 degrees above
normal.  The next shortwave in line dips into the Great Plains
Tuesday afternoon/evening time frame.  This wave is stronger than
the one coming through Sunday night and between the stronger
synoptic forcing and a bit more moisture return ahead of the front,
we should see some precipitation.  Forecast instability shows as
much as 350-900 J/kg of MUCAPE ahead of the front so thunderstorms
still look like a good forecast Wednesday into Wednesday evening.
Looks like there may be some trailing precip behind the front, but
PoPs do drop off quickly after FROPA after 06Z Thursday.

Remainder of the medium range looks quiet with temperatures near or
a few degrees above normal.  Guidance has another cold front moving
into the area next Saturday or Sunday, but there`s little agreement
between medium range models for timing so am sticking with a dry and
relatively warm forecast on for next Saturday.



.AVIATION...  (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1236 PM CDT Sat Oct 22 2016

High pressure in control at the SFC and aloft will produce clear
skies thru the prd. The center of the SFC ridge will remain to
the S/SE thru the prd keeping winds S/SW. An upper level
disturbance will pass to the N of the area Sunday. The LLJ will
ramp up across the area tonight in advance of the upper level
disturbance which is fcst to produce LLWS after midnight. The LLWS
is expected to continue until the winds pick up Sun mrng. The
upper level disturbance will drag a cold front thru the area
tomorrow aftn. Due to very dry air...FROPA is expected to be dry.
SFC winds are fcst to become SW as the bndry approaches and may
become gusty across cntrl/NE mo and W cntrl IL by late Sunday
mrng due to a tightening pressure gradient as the cold front
approaches. Warmer temps tonight and light sthrly flow should
keep river valley steam fog from forming.


VFR fcst thru the prd. Marginal LLWS is expected tonight after
midnight as the LLJ ramps up...and should continue until SFC winds
pick up Sun mrng. An upper level disturbance will drag a cold
front thru the terminal late Sun aftn but due to a lack of
moisture FROPA is expected to be dry.



Saint Louis     55  79  50  67 /   0   0   0   0
Quincy          51  74  46  64 /   0   0   0   0
Columbia        51  75  47  67 /   0   0   0   0
Jefferson City  51  76  45  69 /   0   0   0   0
Salem           48  74  47  66 /   0   0   0   0
Farmington      50  75  48  68 /   0   0   0   0




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