Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 201201
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
701 AM CDT Sat May 20 2017

.SHORT TERM...  (Through Late Tonight)
Issued at 343 AM CDT Sat May 20 2017

As individual storms move northward this morning MCS continues to
track east, exiting forecast area by midday. Then will see
redevelopment as surface low lifts northward through Iowa, dragging
cold front through forecast area late this afternoon/evening. Storms
to finally taper off after midnight tonight.

As for temperatures today, since we are starting out cooler than
originally forecast, in the upper 40s to mid 60s, went close to
guidance or even a degree or two lower for highs due to cloud cover
and precipitation. Only fly in ointment is as surface low lifts
northward today, it will lift stalled warm front back north through
region, so if clouds thin out, even a little, temps could be warmer
than we are forecasting. For now have highs in the 70 to 80 degree
range. Lows tonight will be in the upper 40s to upper 50s.

Byrd

.LONG TERM...  (Sunday through Friday)
Issued at 343 AM CDT Sat May 20 2017

(Sunday through Monday)

Period begins with the cdfnt well east of the CWA with the sfc low
in central WI and the sfc ridge building into the region.

Behind the fnt, a much cooler sfc ridge will build into the region
for Sun. This ridge will keep the area dry with temps struggling to
reach the 70s. While deeper mixing is still expected, have trended
slightly cooler on Sun due to expected cool 850 mb temps. Mon shud be
slightly warmer with 850mb trof moving ewd allowing slightly warmer
temps into the region. However, did not go too warm with clouds
expected to spread into the area and a leading s/w bringing precip
to the area.

(Tuesday through Friday)

Mdls begin the period in fairly good agreement. By the middle of
next week, differences appear, tho mainly timing issues. After the
leading s/w mentioned above pulls ewd out of the region, a fast
moving clipper system is expected to move into the area.

With the region under persistent NW flow and a strong sfc ridge
likely settling south of the region, expect temps to be well below
seasonal avg for much of next week.

Tilly
&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 655 AM CDT Sat May 20 2017

MCS complex continues to move east and should move out of taf
sites by 15z-17z timeframe. Otherwise, dealing with IFR/MVFR cigs,
which should improve to VFR. Will see another round of storms this
afternoon, mainly after 21z for STL metro area as cold front moves
through. This round to move out by 03z Sunday. As for winds, to
persist from the south, then veer to the southwest ahead of front.
Once front moves through, winds to veer to the west.

SPECIFICS FOR KSTL:
MCS complex continues to move east and should move out of metro
area by 15z. Otherwise, dealing with IFR/MVFR cigs, which should
improve to VFR. Will see another round of storms this afternoon,
mainly after 21z for STL metro area as cold front moves through.
This round to move out by 03z Sunday. As for winds, to persist
from the south, then veer to the southwest ahead of front. Once
front moves through, winds to veer to the west.

Byrd
&&

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

$$

WFO LSX



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