Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 261018
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
418 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 06z TAFs through 06z Thursday Night)
Issued at 1140 PM CST Wed Nov 25 2015
Ceilings across the FA have increased throughout the evening as
some lower level dry air as worked north across the region.
However, both RAP and NAM low level RH progs are forecasting
renewed saturation during the predawn hours. Since SREF MVFR cig
probabilities are also coming up from southwest MO into west
central IL during the morning hours on Thursday, have introduced a
TEMPO for MVFR ceilings (1500-2000 ft) during the morning at both
KCOU and KUIN. Some lowering of ceilings are also expected in the
STL Metro area, but believe here the bases will remain above 3kft.
Strong southerly low level flow also persists, so will maintain
LLWS in the forecast until gusts come up early Thanksgiving
Precip is going to remain a hit and miss proposition. Spotty
showers currently extending from mid MO to central IL will likely
persist for several hours, and it`s certainly possible that
additional spotty, light, WAA-driven showers will reform over the
northwest half of the CWA throughout the predawn and morning hours
on Thursday. However, it certainly appears that the main rain
threat will be entering the area tomorrow evening, and
especially after 06z, as cold front finally pushes into western
sections of the CWA. Not only will the rainfall become heavier
and widespread, but ceilings and visbilibites will likely take a
nose dive with FROPA at both KCOU and KUIN after 06z.
Specifics for KSTL: VFR ceilings aoa 4kft are expected overnight
and into most of Thanksgiving Day. Strong low level jet will
maintain LLWS threat until mixing commences and transfers some of
the higher winds to the surface..in the 12-15z time frame.
.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-