Area Forecast Discussion
Issued by NWS Tulsa, OK

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FXUS64 KTSA 211146

Area Forecast Discussion
National Weather Service Tulsa OK
646 AM CDT Sat Oct 21 2017

MVFR ceilings and breezy southerly winds across much of the CWA during
the morning hours are expected to lift back to just within the
VFR category this afternoon ahead of a cold front approaching the
CWA. Thunderstorms are expected to develop along the front late
this afternoon and spread across the CWA this evening and tonight.
Periods of IFR/MVFR conditions and strong variable winds will be
possible within the stronger storms along/near the leading line
with MVFR conditions...northwesterly winds and decreasing
thunder/rain chances behind the front. Will carry tempo groups for
timing of the stronger storms. Conditions look to begin lifting
back to VFR/clearing out across Northeast Oklahoma late in the TAF


.PREV DISCUSSION... /Issued 320 AM CDT Sat Oct 21 2017/


The main items of interest for this morning`s forecast will be
severe storm and heavy rain potential late today and tonight with
a cold front, and rain chances/temps with a strong front late next

Broad western CONUS trough is marching toward the Plains this
morning. A pocket of higher PV was located near the Four Corners
near the basal portion of the parent trough. This energy will move
out into the central/southern Plains later today and will help
provide lift along with the associated Pacific front to produce
widespread storms across the region thru tonight.

The latest short term hi-res guidance indicates some semi-discrete
cell development between 21z and 00z to the west/northwest of
Tulsa, where the greatest threat for hail will be with this event.
An isolated tornado is possible as well. Storms should quickly
grow upscale into a squall line by the time they reach Tulsa and
will continue to march south and east from there thru the night.
Some hi-res guidance indicates there will be potential for some
QLCS tornadoes where segments of the line can bow out to the east
and northeast. This threat will be greatest to the west of highway
69 in northeast Oklahoma. It will be interesting to see how the
supercells that are expected to develop across central OK evolve,
because as they become a portion of the eventual squall line,
they could bring the best threat for QLCS tornadoes as the system
moves into northeast OK. The line should generally decrease in
intensity as it moves into Arkansas and southeast Oklahoma owing
to decreasing instability after midnight.

Given the progressive nature of the system, the flash flood threat
will be localized at best. However, broad 1 to 2 inch rains over
the region may cause a few river points to flood.

There will be a temperature roller coaster next week with
primarily tranquil weather. After a mild start to the work week
Monday, cooler temps are expected Tuesday behind a polar cold
front which will push thru Monday night. Another quick warm-up is
expected thru Thursday ahead of the next system.

There is a lot of uncertainty regarding the evolution of the upper
flow pattern late next week and into the weekend. One thing is
fairly certain. Some shortwave energy is expected to dive
southeast across the middle of the country late next week and will
force another strong polar cold front thru the region. The
Canadian and GFS keep this system a progressive open wave and
suggest little in the way of precip for the area. The 00Z ECMWF is
following in the footsteps of the 12Z run, closing the system off
well to our west and is much wetter going into next weekend. Given
the uncertainty, will keep the chance PoPs from the consensus
guidance for Friday with the front, and will maintain low PoPs
going into the weekend. The temperature forecast is no walk in the
park either during this time frame. Started with consensus
forecast and made adjustments.



TUL   79  52  71  44 /  30 100  10   0
FSM   78  59  70  46 /  20 100  40  10
MLC   80  55  70  43 /  20 100  10   0
BVO   77  50  72  38 /  60 100  10   0
FYV   74  54  64  38 /  20 100  30  10
BYV   74  55  65  44 /  20 100  40  10
MKO   79  53  69  44 /  20 100  20   0
MIO   77  51  68  43 /  10 100  20   0
F10   79  53  70  45 /  20 100  10   0
HHW   82  58  71  47 /  20 100  30  10




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