Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 251731
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1231 PM CDT Sat Oct 25 2014
.SHORT TERM: (Through Late This Afternoon)
Issued at 308 AM CDT Sat Oct 25 2014
Primary focus this morning will be on fog. Believe fog will continue to
slowly advect southeastward behind a weak cold front. By mid-morning...
expect diurnal effects to alleviate concerns for dense fog with remnant
stratus quickly scattering out and then dissipating by midday. A mostly
clear sky is forecast for the rest of today with high temperatures
about 5 degrees warmer than yesterday.
.LONG TERM: (Tonight through Friday)
Issued at 308 AM CDT Sat Oct 25 2014
(Tonight - Monday Night)
Surface ridge will come across the region tonight with light winds.
Appears to be more of a river valley fog setup as strong radiational
cooling should be the rule. More widespread fog is not expected at this
time as lower dewpoints seep southwestward from the Great Lakes.
For mins tonight...leaned a bit toward cooler guidance due to nearly
ideal radiative conditions...especially across the eastern Ozarks
where NWP guidance notoriously has a warm bias.
High temperatures appear challenging for the day on Sunday. Timing of
a warm front moving through the region is a bit uncertain with the
NAM model nearly 6 hr slower than the GFS. Leaned toward the faster
GFS (and thus warmer) solution due to forecast leeside cyclogenesis...
building mid/upper level heights...and lack of precipitation/convection
to retard the northward progression of the warm front. Still looks like
a decent temp gradient across the area however from southwest to northeast.
Expect highs reaching the mid 80s for portions of central Missouri to
low 70s across south-central Illinois.
One last summer-like day is in store on Monday ahead of an approaching
cold front from the northwest. Went above warmest guidance yielding highs
in the 80s nearly areawide as will range from +15-+19C at 850 hPa.
Cold frontal timing looks ~3 hrs quicker on tonight`s models runs than
last night. Consequently...timing of highest PoPs has shifted southeastward
a bit faster as well through Monday night.
(Tuesday - Friday)
Cooler...more seasonable weather looks in store for the rest of the work
week with highs in the 60s through Thursday. Models forecast an impulse
to come through the mid/upper Mississippi Valley on Thursday with slight
chances of showers. Models diverge greatly Friday and beyond but does
appear cooler weather will be ushered in for Halloween and into the
beginning of next weekend with the potential for a widespread frost/freeze
looming beyond the valid forecast period.
.AVIATION: (For the 18z TAFs through 18z Sunday Afternoon)
Issued at 1220 PM CDT Sat Oct 25 2014
VFR conditions expected through the overnight hours at all TAF
sites. A weak cold front across northern Missouri will sag
southward as high pressure builds in from Nebraska. Light and
variable surface winds will become light northerly this afternoon. Some
stratus based at around 2000 feet may creep into the area from
southwest to northeast on Sunday morning as a warm from
approaches. For now, will keep cloud cover at scattered coverage,
and brief evening shift to watch for possible inclusion of an MVFR
deck if later model output continues to indicate this. Light
northerly winds will veer overnight into Sunday as the surface
high moves quickly off to the east and surface low pressure
develops over the plains states.
Specifics for KSTL:
VFR conditions expected through at least 12Z Sunday with light
north winds. Areas of MVFR ceilings to 2000 feet may move across
the TAF site after around 18Z Sunday, and later updates may require
inclusion of a prevailing MVFR ceiling. Winds will veer overnight
and become southeast during the day Sunday.