Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 160828
AFDLSX

Area Forecast Discussion
National Weather Service Saint Louis MO
328 AM CDT Sun Apr 16 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 327 AM CDT Sun Apr 16 2017

Cold front over northeastern Iowa extends southwestward through
northwestern Missouri as of 07z. Ahead of front, showers and storms
have finally begun to move into northern portions of the forecast
area. In the meantime, a MCS complex over western MO is weakening,
with storms associated moving into central MO. So main forecast
question for the morning hours, is how fast will activity move to
the east and southeast across region and what kind of coverage will
it be. For now will see precipitation chances diminish by 12z along
I70 corridor and become scattered.

By late morning through the afternoon hours, will see another wave
of storms develop along frontal boundary, mainly along and south of
I70, as frontal boundary slowly sinks to the south. With increasing
instability, decent lapse rates and plenty of low level moisture,
could see some strong to severe storms along and south of I70 this
afternoon and evening, with the main threats being large hail and
damaging winds. Despite clouds, precipitation and northerly winds,
will still see highs in the low to mid 70s today.

Tonight, models indicating that MCS development will be a bit
further north than previous model runs. So will see MCS develop over
eastern Kansas and track east southeast through Missouri. So raised
pops a bit for areas along and south of I70. Cooler temps expected,
but still a bit above normal for this time of year, in the upper 40s
to upper 50s.

Byrd

.LONG TERM...  (Monday through Saturday)
Issued at 327 AM CDT Sun Apr 16 2017

Focus thru the forecast period remains PoPs. Mdl solns are in fairly
good agreement thru the short term. However, still have low
confidence in timing of precip overall, esp after about 48 hrs, due
to poor consistency from one cycle to the next.

The week active starts with an MCS across ern portions of the CWA
and exiting thru the morning hrs. Believe the GFS is too far north
based on where the effective sfc boundary shud be and best forcing
and have trended PoPs further south and east. With the sfc ridge,
centered over ern Canada, building into the region, the remainder of
Mon and Mon night shud be dry with ely flow at the sfc.

Have continued warm trend on Tues as sly flow returns with swly
850mb flow. Have continued this warm trend into Wed despite mdl
differences, trending twd a ECMWF/GEM consensus.

Mdl differences continue to increase beyond and is difficult to pin
down precip or temp trends. Mdls have been hinting at a deep low
impacting the region late this week into the weekend. Have fairly
high PoPs for this late in the forecast, but have kept out of cat
PoPs for now.

Tilly

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1202 AM CDT Sun Apr 16 2017

Ongoing SHRA/TSRA in Iowa have made slower southeastward progress
than previously anticipated, and the onset of SHRA/TSRA at the
terminals for this set of TAFs has therefore been delayed by
several hours compared to the previous set of TAFs. A broken line
of SHRA/TSRA is still expected to move through the terminals
during the first 0-12 hours. The slower movement of the cold front
means that afternoon redevelopment of SHRA/TSRA near the front
after 18z may affect the St. Louis metro area terminals if the
front has not moved through by then. Expect MVFR conditions
during SHRA/TSRA and for a period of time after precipitation has
ended due to lower ceilings. Initially southwest winds at TAF
issuance will turn westerly with FROPA and then become
northwesterly to northerly behind the front.

Kanofsky

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     74  54  70  53 /  50  40  50   5
Quincy          72  51  72  51 /  10  10  10   5
Columbia        73  53  70  53 /  40  40  40   5
Jefferson City  73  54  70  54 /  50  50  40   5
Salem           74  54  68  50 /  60  40  60   5
Farmington      72  55  68  53 /  70  50  60  10

&&

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

$$

WFO LSX



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