Area Forecast Discussion
Issued by NWS St. Louis, MO
FXUS63 KLSX 081711
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1211 PM CDT THU OCT 8 2015
.SHORT TERM: (Through Tonight)
Issued at 304 AM CDT Thu Oct 8 2015
Forecast focus thru this period will be precip chances.
Trends mentioned yesterday continue today with latest guidance.
Mdl solns continue to suggest region will remain cut off from Gulf
moisture. Mdls also suggest the upper trof out of sync with the
sfc fnt across the area. Believe better chances for precip will
exist E of the CWA with the sfc low and better upper level
dynamics as well as to the W with better low level forcing and a
stronger s/w within the trof. Still believe precip will develop
along the fnt, but coverage continues to look less. Have therefore
lowered PoPs closer to latest MOS guidance. As for timing, appears
SHRA with isod to sct TS will develop across srn IA late this
afternoon and push swd into nrn portions of the CWA into the
evening hours. This precip shud gradually dissipate. However, as
the upper trof approaches, it appears precip will switch to more
stratiform. Timing of this remains uncertain and have kept lower
PoPs further nwd to account for it.
As for temps today, while the upper low over nrn Mexico is
expected to drift swwd today, a leading s/w currently over ern
NEB/KS is expected to provide ample cloud cover thru at least the
morning hours. With less lower and mid level clouds, expect temps
to rise into the 80s with swly flow at low levels. Have trended
twd the cooler guidance again today due to questions of cloud
cover, but also due to the amount of CU that developed and temps
across the Plains yesterday.
Temps tonight will be difficult to pin down as the fnt pushes swd
tonight. Generally, trended cooler across the nrn third and warmer
across the srn third based on cloud trends and timing of fropa.
.LONG TERM: (Friday through Wednesday)
Issued at 305 AM CDT Thu Oct 8 2015
Same precip questions mentioned above continue into Friday
morning, perhaps into the afternoon. Trended cooler for Fri and
Sat as the sfc ridge builds into the region. Sly to swly sfc flow
returns quickly by Sun with the thermal ridge building into at
least wrn portions of the CWA into next week. Mdl solns continue
to differ slightly on timing of a dry fropa on Mon.
Overall, trended above seasonal average thru the forecast period
with the exception of Tues as the sfc ridge builds into the area.
This cooler period is expected to be brief as swly flow returns by
Wed ahead of another weak and dry fnt.
.AVIATION: (For the 18z TAFs through 18z Friday Afternoon)
Issued at 1152 AM CDT Thu Oct 8 2015
A cold front extending from a surface low in northwestern
Wisconsin southwest through southeastern Nebraska will move
southeastward through the taf sites this evening. The cold front
should move through STL around 05Z tonight. The swly surface wind
will veer around to a nwly direction after fropa. There will
likely be a broken line of showers along and just behind this
front. For now will just include VCSH in the UIN and COU tafs for
early evening, and for the St Louis metro area late this evening
into the overnight hours as it appears that most of the showers
should be on the light side with only scattered coverage. Post
frontal low level cloudiness can be expected Friday morning,
possibly briefly dropping into the MVFR catagory.
Specifics for KSTL: Will continue with VCSH in the STL taf for
late evening into the overnight hours as scattered, mainly light
showers are expected as a cold front moves through the area. The
swly surface wind will veer around to a nwly direction late
tonight after fropa. Post frontal, low level cloudiness can be
expected on Friday, possibly dropping into the MVFR catagory for a
brief period of time.