Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 231936
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
236 PM CDT Wed Apr 23 2014

.SHORT TERM:  (Through Late Tonight)
Issued at 236 PM CDT Wed Apr 23 2014

(Tonight)

Mid/upper level ridge axis will pass overhead early tonight with next
system organizing over the south-central Plains. Expect an area of showers
and thunderstorms to organize overnight aided by strong forcing for
large-scale ascent via deepening trough and strong low-level moist/warm
advection. This area of showers and storms should stay west of the area
tonight...but may approach portions of central and northeastern Missouri
by daybreak. Sky cover should increase overnight ahead of aforementioned
system with brisk southeasterly winds continuing throughout the night.
For these reasons...went a few degrees above warmer MAV guidance in most
locations.


Gosselin


.LONG TERM:  (Saturday through Tuesday)
Issued at 342 AM CDT Wed Apr 23 2014

While the medium range guidance is coming into better agreement on
the overall synoptic pattern, the smaller scale is still unclear.
Generally, a secondary cold front will dip south across the Upper
Midwest driven south by the last vestiges of Thursday`s shortwave.
The front will stall somewhere across the Midwest on Saturday,
though models can`t make up their minds where.  GFS stalls the front
across south/southwest Missouri Saturday morning, while the ECMWF
stalls it out over northern Iowa.  The GEM is right about in the
middle stalling the front over northern Missouri.  All three models
have some low level baroclinicity over our area, whether it is the
primary baroclinic zone associated with the front (GFS/GEM) or a
secondary baroclinic zone left over from the Pacific airmass which
will be exiting to the east (EC).  Warm advection begins Saturday
morning with a 30+ kt low level jet pointed at this baroclinic zone
and all three models print out some light precip.  Have therefore
kept chance pops going in central Missouri, and would not be
surprised if subsequent shifts need to bump up pops a bit more
across the area if model trends become more consistent.

The front remains stalled somewhere between Springfield Missouri and
Davenport Iowa depending on which model you believe through Monday
as the longwave trof over the Pacific moves inland, and becomes
negatively tilted over the Rockies and Great Plains.  A strong
surface low develops as a result and it moves into the Mississippi
Valley Monday night into Tuesday.  The upper trof cuts off and
becomes stagnant while the surface low tracks across Missouri into
the Ohio Valley Tuesday.  Pattern is more reminiscent of late Fall
or Winter than mid to late Spring.  Unsure how likely this is to
happen, but this is at least the second run in a row that I`ve seen
do this.  Will have to wait and see, but right now it looks like a
cold/wet end to April.

Carney

&&

.AVIATION:  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1223 PM CDT Wed Apr 23 2014

Area of showers currently over western Missouri is expected to weaken
this afternoon and is not expected to affect KCOU or KUIN at this
time. Main impact will be increasing midlevel cloudiness at
terminals. Southeast winds are expected to prevail through the
night ahead of next system which will move eastward. Southerly
low-level jet of 40-45 knots near 2000 feet AGL over central
Missouri and west- central Illinois could produce low- level wind
shear and added mention for KCOU and KUIN. For tomorrow...another
area of showers with embedded thunderstorms is expected to move
into the area from west to east ahead of a cold front from late
morning into the early afternoon. Actual frontal passage and
accompanied wind shift is likely to be after this valid forecast
period.


Specifics for KSTL:

Increasing midlevel cloudiness is expected through the afternoon at
the terminal. Southeast winds are expected to prevail through the night
ahead of next system which will move eastward. Low-level jet axis
should stay to the west of KSTL precluding mention of LLWS. For
tomorrow...another area of showers with embedded thunderstorms is
expected to affect Lambert Field around midday. However...actual
frontal passage and accompanied wind shift is likely to be just after
this valid forecast period.

Gosselin

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     52  73  45  81 /  10  80  40   0
Quincy          50  66  43  79 /  20  80  20   0
Columbia        54  71  44  80 /  60  80  10   0
Jefferson City  54  71  44  80 /  50  80  10   0
Salem           48  74  46  78 /   5  70  80   0
Farmington      47  75  46  78 /  10  80  40   0

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX






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