Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KLSX 262359

559 PM CST THU NOV 26 2015

.SHORT TERM: (Through Saturday)
Issued at 333 PM CST Thu Nov 26 2015

A strong wound-up storm system over the Great Basin region of the
western CONUS is expected to move little during this period,
maintaining an active southwest flow aloft over our region, and
shooting out pieces of energy or distrbances our way as well.

The first of these disturbances is expected to arrive shortly after
sundown this evening, with essentially a near continuous train thru
late Saturday after that.  The effects of the rainfall that this
brings will be further augmented by a slow moving cold front thru
midday Friday and rich moisture from the Gulf of Mexico, some of
which will continue to overspread north of the front after it
passes, into the cold air.

Despite much cooler air ushering in behind the cold front,
temperatures are expected to stay above freezing for most areas thru
this entire period and will keep pcpn-types as all rain.  The
exception is expected to be in parts of northeast MO and west-
central IL late Friday night and early Saturday morning, where temps
will be around the freezing mark.  Fortunately, much of the pcpn by
that time should be to the south with only light spotty pcpn
currently anticipated.

Otherwise, the main concern will be the prolonged period of heavy
rainfall--especially for parts of southeast MO and far southern IL--
where rainfall totals may top 4 inches into Saturday.  The Flood
Watch will continue, with the addition of Audrain and Lincoln
counties in MO, where similar QPF and contingency forecasts for area
rivers and streams exist.  An expansion into Marion, Bond, and
Fayette counties in IL was also considered, with timing of onset
enough to give it one more look before making a final call.  Even
though rainfall chances remain high into Saturday afternoon and into
Sunday for southeast MO and southern IL, rainfall amounts look light
enough to justify ending the FFA on Saturday as it currently does.

Temps will be quite mild for late November ahead of the front, but
will rapidly drop to below average for daytime maxes behind it, with
readings in some areas not getting out of the 30s.  Fortunately,
plenty of warm air aloft should keep the pcpn as rain unless surface
temps can slip below 32F.


.LONG TERM: (Sunday through Next Thursday)
Issued at 333 PM CST Thu Nov 26 2015

Model solutions have come into much better agreement on mass
fields here, with the wound-up storm system ejecting into the
Plains on Monday and slowly tracking east--north of our region on
Tuesday-- with northwest flow aloft to follow on Wednesday. Large
model spread then resumes for next Thursday, where the EC shows a
much deeper storm trying to take shape for the mid-MS valley than
the GFS.

Either way, pattern is very supportive of keeping the very cold air
locked in Canada.  The approach of the main storm system Monday will
allow for one more decent rain chance at all locations after being
largely confined to southern MO and southern IL again on Sunday,
with dry wx for a change Tuesday and Wednesday as high pressure
builds in, and probably will continue into Thursday.

Temps look to be around average for the November-December interface.



.AVIATION:  (For the 00z TAFs through 00z Friday Evening)
Issued at 555 PM CST Thu Nov 26 2015

Large area of rain stretching from s WI into the southern
Plains..and the associated cold front...will continue their slow
eastward march overnight and into the day on Friday. Timing of
onset of rain as well as FROPA in 18z TAF set still looks quite
good, with rain moving into the KCOU and KUIN areas over the next
few hours, and pushing into STL Metro area around 06z, with FROPA
occurring 4-6 hours later. While ceilings/vsbys will likely dip
into MVFR range in the steadier rain just ahead of the cold front,
believe that IFR cigs will develop and/or advect into an area once
FROPA occurs, and forecast of ceilings dipping to around 500 feet
with FROPA is the primary change to earlier forecast trends. Low
level jet will produce LLWS conditions over STL Metro for most of
the night...with winds around 2kft 40-45kts.

Specifics for KSTL: VFR conditions are expected early this
evening. However, rain should begin to move into the area late
this evening with ceilings and vsbys lowering into MVFR range by
06z. Conditions should continue to deteriorate during the predawn
hours as the steady rain persists and strong cold front moves in
by around daybreak, and expect IFR cigs and low end MVFR vsbys in
rain throughout the morning hours on Friday. Moderate to
occasionally rain is anticipated Friday morning.

Intensifying low level jet should maintain LLWS threat for most
of the night...with southerly winds of 40-45 kts around 2kft.



MO...Flood Watch from midnight CST tonight through Saturday morning
     FOR Crawford MO-Franklin MO-Jefferson MO-St. Charles MO-St.
     Louis City MO-St. Louis MO-Washington MO.

     Flood Watch from Friday morning through Saturday morning FOR
     Iron MO-Madison MO-Reynolds MO-St. Francois MO-Ste.
     Genevieve MO.

     Flood Watch through late Friday night FOR Audrain MO-Boone MO-
     Callaway MO-Cole MO-Gasconade MO-Lincoln MO-Moniteau MO-
     Montgomery MO-Osage MO-Warren MO.

IL...Flood Watch from midnight CST tonight through Saturday morning
     FOR Madison IL-Monroe IL-St. Clair IL.

     Flood Watch from Friday morning through Saturday morning FOR
     Clinton IL-Randolph IL-Washington IL.



WFO LSX is the U.S. government's official web portal to all federal, state and local government web resources and services.