Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 230430
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1130 PM CDT Wed Apr 22 2015
.SHORT TERM: (Through Late Tonight)
Issued at 324 PM CDT Wed Apr 22 2015
An elongated ridge of high pressure which stretches from the
east-central Great Plains up into central Canada will continue slide
east tonight. The southern lobe of anti-cyclonic rotation is
centered over southeast Nebraska and northeast Kansas and will move
over central Missouri by 09-12Z Thursday morning. This will result
in light and variable wind across much of the forecast area.
Upstream temperatures this morning fell into the low to mid 30s
across southeast Nebraska and northern Kansas. MOS guidance shows
similar temperatures so this seems very reasonable. With light wind
and a mostly clear sky, expect areas of frost to form especially in
low-lying/sheltered areas. Will therefore go ahead and issue a
frost advisory for the entire area since the growing season is in
.LONG TERM: (Thursday through Next Wednesday)
Issued at 324 PM CDT Wed Apr 22 2015
Even with winds being light and variable under surface ridge on
Thursday, will see temperatures warm up into the low to mid 60s
under mostly sunny skies.
Then by Thursday night, surface ridge to move off to the east ahead
of next weather system. With strong low level flow from the south to
southwest will see low level moisture return ramp up, but still feel
that precipitation will be slow to move into forecast area due to
weak upper level ridge. Just have slight chance pops after 06z
Friday for western portions of forecast area. Lows will range from
the upper 30s far east to the mid 40s far west.
Models for the most part are on the same track with this system,
though the 12z GFS and ECMWF have a rather wonky track for the
surface low compared to the NAM. For now will keep with similar
timing and placement to previous forecast package with precipitation
on the increase during the day Friday. Best chance will be Friday
night through Saturday, before tapering off and exiting Saturday
evening. Depending on track of surface low and precipitation
coverage, will see a wide range of temperatures on Saturday, from
the mid 50s far north to the low 70s far south.
Surface ridge briefly builds in by Sunday with dry conditions
through Monday before next chance of rain moves in Monday night
through Wednesday. Confidence is low on exact details and timing of
the rounds of rain that will be possible with this system, so just
kept slight chance/low chance pops through the period. Temperatures
to remain cool with highs in the 60s and lows in the 40s.
.AVIATION: (For the 06z TAFs through 06z Thursday Night)
Issued at 1130 PM CDT Wed Apr 22 2015
VFR conditions and dry wx will prevail at the TAF sites thru the
valid period. Otherwise, light NW surface winds will become
variable in direction from west to east during the course of
Thursday, and eventually settle from the east.
Specifics for KSTL: VFR and dry thru the period. Light NW surface
winds will become variable in direction late Thursday afternoon
for a few hours as a high pressure RIDGE moves in before becoming
easterly by late evening.
MO...FROST ADVISORY from 4 AM to 8 AM CDT Thursday FOR Audrain MO-
Boone MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-
Gasconade MO-Iron MO-Jefferson MO-Knox MO-Lewis MO-Lincoln
MO-Madison MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO-
Osage MO-Pike MO-Ralls MO-Reynolds MO-Shelby MO-St. Charles
MO-St. Francois MO-St. Louis City MO-St. Louis MO-Ste.
Genevieve MO-Warren MO-Washington MO.
IL...FROST ADVISORY from 4 AM to 8 AM CDT Thursday FOR Adams IL-Bond
IL-Brown IL-Calhoun IL-Clinton IL-Fayette IL-Greene IL-
Jersey IL-Macoupin IL-Madison IL-Marion IL-Monroe IL-
Montgomery IL-Pike IL-Randolph IL-St. Clair IL-Washington