Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 200910
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
410 AM CDT Thu Apr 20 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 406 AM CDT Thu Apr 20 2017

Not a lot of change from the prev forecast thru tonight. Continued
warm trends for the ern half to two thirds of the CWA for today.
While there shud be a mostly bkn cloud deck today, the area shud
begin the day quite warm. With continued CAA tonight and clouds
clearing across nrn portions of the CWA, have trended aob the cooler
MOS while trending slightly warmer further south.

Mdl solns do not have a great handle on how precip will evolve
today. Expect ongoing SHRA with sct TS to continue thru the morning
hrs. TSRA shud develop ahead of the fnt, across ern and srn portions
of the CWA, by early afternoon with a weak CAP in place and heating.
Severe parameters are not great and think CAPE is overdone in many
mdl solns, wud expect pockets of greater instability to exist in
this area. With a weak CAP, storms shud initiate before much CAPE
can build, limiting the severe threat. That said, a threat will
remain with unidirectional hodographs allowing for storms to merge
with bowing segments possible. Believe main threat will be wind if
storms can become organized.

Tilly

.LONG TERM...  (Friday through Wednesday)
Issued at 406 AM CDT Thu Apr 20 2017

Models remain in pretty good agreement with upper level shortwave
over Central Plains sliding east, dragging surface low along stalled
boundary just south of forecast area.  Rain chances to increase and
spread northward through out the day and into the overnight hours on
Friday. By Saturday, as system begins to lift off to the east
northeast, will see showers gradually taper off, especially by
Saturday evening. A few issues to deal with are qpf with this system
and temperatures, especially highs on Saturday. With front south of
forecast area, cloud cover, precipitation and northeast winds, it
will be a rather chilly rain with highs only in the upper 40s to mid
50s Saturday. Warmest temps will be across far northern portions of
forecast area where the lowest pops are. As for qpf, storm total
amounts of about an inch, along I70 corridor, to between 2 and 3
inches over southeast MO/southern IL can be expected. But it is over
a 3 day period, so feel that a flood watch is not warranted at this
time.

Surface ridge to build in beginning late Saturday night, so will see
moderating temperatures for the remainder of the forecast period.
Temperatures to warm back up into the mid to upper 60s on Sunday,
then into the 70s by Tuesday and Wednesday. Extended models have
some timing and placement issues with the next system that will
approach the region by late Tuesday night, Wednesday. For now kept
what Superblend has with increasing chances of rain for this period.

Byrd
&&

.AVIATION...  (For the 06z TAFs through 06z Thursday Night)
Issued at 1150 PM CDT Wed Apr 19 2017

The cold front stretched through northwest MO at 05z and coverage
of showers and storms along the front was rather scattered. The
cold front will move east/southeast overnight and Thursday
accompanied by scattered showers and thunderstorms. Exact terminal
impacts remain difficult to gage given the scattered coverage. I
have continued to indicated a roughly 4 hour window when I think
the best threat will occur, however flight conditions with any
showers or storms could certainly be lower. In addition to a west
to northwest wind shift, there could also be a brief period of
MVFR cigs/stratus accompanying the frontal passage.

SPECIFICS FOR KSTL:

Spotty showers are expected to develop in eastern MO sometime
between 09-12z, however a better threat of showers and possibly
some thunder will be along and ahead of the approaching cold front
during the 15-19Z time frame. Flight conditions with any showers
or storms could certainly be lower than indicated in the TAF at
this time. In addition to a west to northwest wind shift, there
could also be a few linger showers accompanying the frontal
passage.

Glass
&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     76  49  60  45 /  50  10  30  70
Quincy          70  44  59  43 /  40   5  10  50
Columbia        70  47  58  43 /  50  10  40  70
Jefferson City  71  49  59  45 /  60  10  50  70
Salem           79  49  60  45 /  70  30  40  70
Farmington      76  51  57  45 /  70  50  70  90

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$
WFO LSX



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