Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 170827
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
327 AM CDT Fri Apr 17 2015

.SHORT TERM:  (Through Late This Afternoon)
Issued at 327 AM CDT Fri Apr 17 2015

Deep cutoff low over the Four Corners has amplified the upper level
ridge over the mid-Mississippi Valley.  This ridge should hold fast
today as the low moves slowly east into Colorado.  The ridge should
provide enough subsidence to keep the area dry today, and with 850mb
temperatures in the 12-14C range the MOS highs in the upper 70s to
low 80s range look good.  The low will continue drifting northeast
tonight and should be in eastern Colorado by 12Z Saturday morning.
Have slowed PoPs down marginally with only a slight chance edging
into central Missouri this evening, and then low chance overnight.
With increasing clouds and southerly flow, should see overnight lows
only dip into the upper 50s to low 60s.

Carney

.LONG TERM:  (Friday through Next Thursday)
Issued at 307 PM CDT Thu Apr 16 2015

Upper ridge will remain over region on Friday, so kept dry
conditions going with highs in the upper 70s. Then as upper ridge
begins to move east, surface warm front develops south of forecast
area. So will see showers and thunderstorms develop over western MO
and increase in coverage across central MO Friday night and across
rest of forecast area Saturday and Saturday night as warm front
lifts north through region.

Then main upper level shortwave to begin to lift out Sunday with
cold front sliding through region. Decent instability with capes
between 500 and 1500 J/kg as well as decent shear, so SPC still has
15 percent probability of severe weather on Day 4. Precipitation to
taper off Sunday night as front exits region.

Beyond that, weak surface ridge builds with dry and colder weather
expected for the first part of the work week with highs in the 60s.
Then extended models have differing timing and solutions for next
weather system. For now kept slight chance/chance pops for Wednesday
through Thursday.

Byrd

&&

.AVIATION:  (For the 06z TAFs through 06z Friday Night)
Issued at 1147 PM CDT Thu Apr 16 2015

The main forecast issue continues to focus on fog development
overnight. The lingering patches of clouds from 5000-6000 ft and
high clouds spreading across the region lower confidence some, but
not enough to remove the mention from the terminals. Anticipating
that during the overnight hours, areas of fog should develop,
especially from the St. Louis area southeastward into southern IL.
I have delayed the onset from the previous forecast by a few
hours, thinking that it will be after 08-09z before visibilities
lower with potential for IFR flight conditions from around 10-14z.
By mid-morning the fog should dissipate and VFR flight conditions
will dominate with scattered diurnal cu and some high cloudiness.


Specifics for KSTL:

The main forecast issue continues to focus on fog development
overnight. The lingering patches of clouds from 5000-6000 ft and
high clouds spreading across the region lower confidence some, but
not enough to remove the mention from the terminal. Anticipating
that it will be after 09z before visibilities lower with potential
for IFR flight conditions from around 10-14z. By mid-morning the
fog should dissipate and VFR flight conditions will dominate with
scattered diurnal cu and some high cloudiness.

Glass

&&

.PRELIMINARY POINT TEMPS/POPS:
Saint Louis     82  60  77  60 /  10  10  40  80
Quincy          79  58  74  58 /  10  10  40  80
Columbia        80  60  74  59 /  10  30  70  80
Jefferson City  79  60  73  59 /  10  30  70  70
Salem           79  57  75  60 /  10  10  30  80
Farmington      78  59  73  60 /  10  10  50  80

&&

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

$$

WFO LSX






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