Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 211731
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1231 PM CDT Thu May 21 2015

.SHORT TERM:  (Through This Afternoon)
Issued at 340 AM CDT Thu May 21 2015

Widespread low cloudiness in the wake of yesterday`s system
continues to blanket much of the region early today.  Although some
holes have developed in the cloud deck over western IL and central
MO, the true back edge of the cloud deck is currently hugging the
MO-IA border and dropping southeast at ~15 kts.

With the surface ridge working southeast and re-exerting its
influence over the area today, see no reason that the above clearing
trend won`t work across the entire FA during the morning.  Should be
quite a bit of sunshine this afternooon, but also anticipate some
CU/SC to reform in the wake of the clearing due to diurnal heating
of the saturated ground.

Temperatures will remain below average today as the chilly Canadian
airmass continues to exert it`s influence...with highs in the 60s.

Truett

.LONG TERM:  (Tonight through Wednesday)
Issued at 340 AM CDT Thu May 21 2015

Not many changes to the prev forecast thru day 3. Large sfc ridge
remains in control of the wx pattern thru Fri. Mdls prog the sfc
ridge moving ewd out of the region on Fri with upper level ridging
occurring over the area. Differences among guidance begin early with
the ECMWF focusing the LLJ much further E than the other guidance.
All other mdls suggest the LLJ will remain focused on the wrn
fringes of the upper ridge. This soln seems more plausible, outside
from any MCS activity. While the ECMWF soln is possible, have
continued drier trend twd other solns. Regardless, mdls come into
better agreement Sat night as the upper ridge moves slightly E and
the LLJ becomes more focused over the region. This trend continues
thru at least Mon, perhaps longer if mdl trends continue. Confidence
quickly drops for Tues and beyond with differences among guidance
and due to the general flow across the region. Have kept chance PoPs
continuing thru the period.

As for temps, have continued cool temps thru Sat due to the sfc
ridge in place and then, precip/cloud cover expected on Sat. That
said, am somewhat concerned that mdls, esp the GFS, are overdoing
cloud cover. Will monitor trends, but going forecast may be too cool
this weekend if clouds do not materialize. Have temps moderating
thru the remainder of the forecast due to mdls suggesting heights
gradually rising. However, temps will be modified somewhat on any
given day due to cloud cover and precip.

Tilly

&&

.AVIATION:  (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1225 PM CDT Thu May 21 2015

Some lingering low end VFR ceilings possible for first hour or
two at KSTL metro TAFS, but otherwise VFR conditions will prevail
through this TAF forecast period. Winds will continue light northwesterly
to westerly.

Specifics for KSTL: Ceilings just above 3000 feet will likely go scattered
by 19Z or so. Otherwise VFR conditions expected through the
forecast period. Light northwesterly winds will become west by sunset.

Browning

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     65  49  76  57 /   5   0   0  10
Quincy          66  48  74  53 /   5   0   0  10
Columbia        65  45  72  51 /   5   0  10  10
Jefferson City  65  43  73  51 /   5   0  10  10
Salem           63  44  74  54 /   5   0   0   5
Farmington      62  42  72  49 /   5   0   5  10

&&

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

$$

WFO LSX






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