Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 201727
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
ISSUED BY NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1127 AM CST Thu Nov 20 2014
.SHORT TERM: (Through Late This Afternoon)
Issued at 315 AM CST Thu Nov 20 2014
A deep upper level TROF continues to dominate eastern North America,
with resultant NW flow aloft for our region. A region of heavily
sheared vorticity existed overhead but was having no major impact to
our weather thanks to a very dry column. At the surface, a hi
pressure ridge axis extended from the Dakotas into western MO,
giving our region a light westerly flow. Satellite data shows a
ribbon of clouds across northern MO and southern IL, otherwise skies
were clear. Radar data was pcpn-free. Temps were in the 20s for
most locations with a few pockets of upper teens.
NW flow aloft will continue with the area of sheared vorticity
exiting later this morning. The ridge of high pressure at the
surface will then slowly edge into our region. The result should be
dry weather today with mostly sunny skies.
Started with the warmer MAV MOS temps and bumped them up still
further in some areas, especially in southeast MO where there will
be a bit more sun, while further north the clouds will tend to be a
nuisance for a good part of the day. This will yield maxes in the
30s for much of our region, with 40-45 in southeast MO.
.LONG TERM: (Tonight through Wednesday)
Issued at 315 AM CST Thu Nov 20 2014
Surface ridge to begin moving off to the east tonight allowing
winds to become easterly ahead of next weather system. Clouds will
be on the increase, but with easterly flow low temps to still dip
down into the mid teens to mid 20s.
On Friday, forecast remains tricky as the mid levels moisten up by
midday with surface temps slowly warming up to near or just above
freezing. With onset of precipitation could see a bit of sleet
initially as evaporative cooling takes place just off the surface.
Then as temps warm up through the afternoon hours, precipitation to
change over to all light rain.
WAA to kick in Friday night as winds pickup from the south. So will
see steady or slowly rising temperatures through the overnight hours.
Near normal temperatures can be expected through the weekend. The
system continues to strengthen with the best chances for rain
Saturday night and Sunday. Some elevated convection possible,
especially over southern half of forecast area Saturday through
Sunday as surface low deepens and lifts northeast through forecast
Then as system exits region will see colder air filter in on
backside. So lingering precipitation to become a mix of rain and
snow especially for central and northeast Missouri as well as west
central Illinois Sunday night and Monday before tapering off. Highs
will be below normal once again, in the mid 30s to mid 40s Tuesday
.AVIATION: (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1127 AM CST Thu Nov 20 2014
VFR conditions are expected to persist through the next 24 hours
as morning stratus scatters out east of the terminals and mainly
clear skies prevail. West northwest winds will gradually veer to
the north this afternoon, then will become light and variable
overnight. Stratus will begin to build in from the southwest on
Friday morning, but should remain VFR through 18z.
Specifics for KSTL: Skies should remain clear through Friday AM,
then stratus will begin to build in by 17-18z Friday. Ceilings
will initially range from 3-4 kft, then will gradually lower
during the early afternoon hours. By 21-22z, ceilings will drop to
1500 ft or less, and drizzle will become possible slightly after