Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 261209
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
609 AM CST THU NOV 26 2015
.SHORT TERM: (Through Late This Afternoon)
Issued at 316 AM CST Thu Nov 26 2015
Focus continues to be precip chances thru the afternoon.
Expect strong sly winds to continue thru today. A strong swly LLJ is
expected to continue over the region today as well. Mdls continue to
depict broad areas of moisture convergence across the area today.
This is expected to result in light SHRA off and on thru much of the
day. The better chances appear to continue to be across nrn portions
of the CWA. Believe will continue with higher PoPs across this area,
tho expect little accumulation with these SHRA.
That said, the area of more stratiform and somewhat heavier RA shud
be moving into the nwrn portions of the CWA late this afternoon into
the evening hrs.
Another forecast problem for today is temps. While expect extensive
cloud cover across the area, the strong sly flow shud help push
temps warmer. Have trended slightly above the cooler guidance for
.LONG TERM: (Tonight through Wednesday)
Issued at 418 AM CST Thu Nov 26 2015
(Tonight through Saturday )
Not many changes to the prev forecast thru this period. Mdls are in
fairly good agreement and have slowed onset of stratiform precip
this evening. Other main change was to speed up swd progression of
precip tomorrow night into Sat.
Despite this slower onset timing, have kept the Flood Watch as-is
except to extend the watch to 18z Sat. While precip will likely
continue into Sat afternoon, believe the heaviest precip will have
ended, tho a residual flooding threat may linger.
Focus begins to shift to p-type issues late Fri night into Sat
morning, and again late Sat night into Sun morning. As the large
arctic airmass builds into the area, cold air will advect into the
region as precip comes to an end. Have not trended as cold as some
guidance and future forecasts may need to speed up the CAA and pull
the FZRA further swd sooner than the current forecast. There is also
some indication that the low level cold air may be deep enuf that
sleet will also be possible. With sfc temps being warmer, believe
that chances for ice accumulation are low, especially given the low
chance of occurrence. Will need to continue to monitor this time
period and watch trends with future updates.
(Sunday through Wednesday)
Again, not many changes from the prev forecast for this period. The
GEM continues to be a cold soln and have trended twd the warmer
GFS/ECMWF solns. Have continued low PoPs thru Mon due to differences
among mdl guidance. However, it appears all precip shud be out of
the area on Tues.
.AVIATION: (For the 12z TAFs through 12z Friday Morning)
Issued at 543 AM CST Thu Nov 26 2015
Focus for this fcst prd will be timing of onset of precip and
deterioration of CIG/VSBY this aftn/evng. Strong cold front will
push thru the region today and tonight. VFR showers and/or
sprinkles should be fairly widespread thru the day ahead of the
front. Tied diminishing flight categories to the dvlpmnt of the
more persistent rain as the front approaches. Timed low end MVFR
conditions with FROPA...but widespread IFR conditions will be
likely later tonight and Friday behind the front. Due to lower
confidence on the exact timing of FROPA...eventual CIG/VSBY
values and the trend that the IFR conditions are not expected to
dvlp until towards the end of the fcst...decided to hold off
introducing IFR conditions into the TAF attm. Strong sthrly winds
will dvlp today and then switch quickly to the north after FROPA.
Specifics for KSTL:
VFR fcst into this evng with light showers and/or sprinkles thru
the aftn. More widespread showers are expected to dvlp this evng
as a strong cold front approaches the terminal. MVFR conditions
should dvlp as more persistent rain moves into the area tonight.
Tied the low end MVFR conditions to FROPA...though fully expect
there to be widespread IFR conditions on Friday. Strong gusty
sthrly winds will dvlp later this mrng...diminish after 00Z and
then quickly switch to the north with FROPA.
.PRELIMINARY POINT TEMPS/POPS:
Saint Louis 67 52 56 39 / 30 100 100 80
Quincy 66 39 41 32 / 70 100 60 30
Columbia 67 40 42 34 / 70 100 80 60
Jefferson City 68 42 45 35 / 70 100 90 70
Salem 65 56 58 42 / 20 100 100 90
Farmington 64 54 57 39 / 30 100 100 90
MO...Flood Watch from this evening through Saturday morning FOR Boone
MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
Iron MO-Jefferson MO-Madison MO-Moniteau MO-Montgomery MO-
Osage MO-Reynolds MO-St. Charles MO-St. Francois MO-St.
Louis City MO-St. Louis MO-Ste. Genevieve MO-Warren MO-
IL...Flood Watch from this evening through Saturday morning FOR
Clinton IL-Madison IL-Monroe IL-Randolph IL-St. Clair IL-