Area Forecast Discussion
Issued by NWS St. Louis, MO

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431
FXUS63 KLSX 141034
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
434 AM CST Sat Jan 14 2017

.SHORT TERM... (Through Sunday Night)
Issued at 318 AM CST Sat Jan 14 2017

No changes to existing headlines.

A wave of freezing rain was moving across the area early this
morning. Temperatures were in the upper 20s to lower 30s across
the region on the cold side of a stalled boundary which stretched
from AR into TN. Heavier rain rates were observed from time to
time at the NWS office overnight when stronger radar echoes moved
overhead, which is consistent with the +2 SD PW values depicted by
model guidance. Ice accretion is known to be less efficient with
heavier rain rates compared to lighter rain rates, and this may
cause some locations to receive slightly less ice accretion than
would otherwise be expected based solely on a look out the window.

A lull in the rain is expected this afternoon and early this
evening before the next wave of rain develops and spreads into
the area after midnight. The surface temperatures over parts of
southeast MO and southwest IL may have risen above freezing by
the time the overnight rain arrives, and for those locations the
freezing rain threat will have ended. Depending on the location
of the surface freezing line, future shifts may be able to end
the Ice Storm Warning early for some areas.

Temperatures are expected to rise above freezing across the
southern half of the CWA on Sunday. The combination of rising
temperatures and a northward shift of the precipitation axis will
end the threat of widespread freezing rain from south to north on
Sunday/Sunday night.

42

.LONG TERM... (Monday through Friday)
Issued at 318 AM CST Sat Jan 14 2017

A cutoff low near Baja California will rejoin the flow on
Saturday night in response to a shortwave diving down the West
Coast. The former cutoff low will lift northeastward into the
southern plains by 12z Monday. The sfc reflection of this feature
will lift the stalled boundary northward as a warm front on Sunday
night and Monday. Temperatures will warm well above freezing on
Monday within the warm sector. Instability may be sufficient for
isolated to scattered thunderstorms on Monday afternoon and
evening ahead of the system`s cold front.

Models diverge significantly by the middle of the week due to
differences in the speed, timing, location, existence of, and
interaction between several shortwaves.

42

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1140 PM CST Fri Jan 13 2017

CIGs have recently dropped to IFR across COU and the STL metro
sites and should remain in these low clouds thru much of Saturday
with a slight improvement for Saturday evening. UIN should remain
in MVFR CIGs thru much of the valid period, although some of the
IFR to their south may edge them late tonight or early Saturday
morning. Something to watch.

Already "Round 2" of the FZRA event is entering our region,
affecting central MO and COU currently and will spread east and
edge the STL metro sites and UIN soon. This pcpn looks to be more
intermittent and handled with TEMPO groups with VCSH for a longer
duration into early Saturday morning. Another break in the pcpn is
then expected for much of Saturday afternoon and evening before
"Round 3" moves in. It was only mentioned in the 30-hour STL TAF
after 09z.

TES

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Ice Storm Warning until 6 AM CST Sunday for Crawford MO-Iron MO-
     Madison MO-Reynolds MO-Saint Francois MO-Sainte Genevieve
     MO-Washington MO.

     Ice Storm Warning until 3 PM CST Sunday for Audrain MO-Lincoln
     MO-Monroe MO-Pike MO-Ralls MO.

     Ice Storm Warning until noon CST Sunday for Boone MO-Callaway MO-
     Cole MO-Franklin MO-Gasconade MO-Jefferson MO-Moniteau MO-
     Montgomery MO-Osage MO-Saint Charles MO-Saint Louis City MO-
     Saint Louis MO-Warren MO.

     Ice Storm Warning until 6 PM CST Sunday for Knox MO-Lewis MO-
     Marion MO-Shelby MO.

IL...Ice Storm Warning until 6 AM CST Sunday for Randolph IL.

     Ice Storm Warning until 3 PM CST Sunday for Calhoun IL-Greene IL-
     Jersey IL-Macoupin IL-Montgomery IL-Pike IL.

     Ice Storm Warning until noon CST Sunday for Bond IL-Clinton IL-
     Fayette IL-Madison IL-Marion IL-Monroe IL-Saint Clair IL-
     Washington IL.

     Ice Storm Warning until 6 PM CST Sunday for Adams IL-Brown IL.

&&

$$

WFO LSX



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