Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 271157
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
557 AM CST Sun Nov 27 2016

.DISCUSSION...
The November 27-28, 2016 12 UTC TAF discussion follows:

&&

.AVIATION...
Overall, a low confidence aviation forecast through the TAF
period. Generally expect low ceilings with MVFR to IFR flight
conditions to continue at most terminals. Some drizzle and/or mist
is also possible. Gusty winds should prevent the development of
any low visibilities. Scattered showers, perhaps isolated
thunderstorms, are expected to develop across western Oklahoma
later this morning. These showers should progress eastward through
the day. Ceilings should improve across western terminals late
this afternoon; however, MVFR ceilings may persist across central
Oklahoma terminals through the period.

Windy conditions are also expected today, especially across
northern and western Oklahoma/adjacent north Texas. Expect
sustained south to southwesterly winds at 20 to 25 knots, with
gusts over 35 knots possible. Surface winds are expected to veer
and weaken tonight. The highest chance of showers/storms are
expected to stay southeast of any TAF sites tonight.

Mahale

&&

.PREV DISCUSSION... /issued 413 AM CST Sun Nov 27 2016/

DISCUSSION...
Primary forecast concerns are strong winds/rain chances today,
severe weather potential tonight, and the potential for
precipitation toward the end of the week.

A tight surface pressure gradient (~13 mb change in pressure from
Buffalo to Atoka at 21Z) indicates sustained wind speeds of 25 to
30 mph with higher gusts will be possible today, especially
across northern and western Oklahoma/adjacent north Texas. As a
result, went above blended guidance for wind speeds and opted to
issue a wind advisory. One mitigating factor, especially across
the east, will be cloud cover/precipitation. That should reduce
the potential for mixing. There will also be the potential for
elevated to near-critical fire weather conditions late this
afternoon. The overall threat will be modulated by how far
eastward the drier air shifts; however, parts of Harper and Ellis
Counties could experience these conditions this afternoon.

A fast-moving vort max is expected provide sufficient
ascent for showers and perhaps isolated thunder starting later
this morning across western Oklahoma and into northern/central
Oklahoma as it lifts northeastward this afternoon. Though the
forecast QPF is expected to be low (<= 0.10"), the probability of
receiving measurable precipitation is relatively high (>50%).
Therefore, opted to increase the probability of rain across
western Oklahoma late this morning and central/northern Oklahoma
this afternoon.

There might be a lull in precipitation late this afternoon into
the evening behind the initial wave. However, a second vort
max/short wave trough is expected to provide additional ascent
tonight--primarily across southeast Oklahoma. Environmental
conditions will be favorable for isolated strong to severe
thunderstorms as elevated instability increases after midnight.
Effective bulk shear and 0-1 km shear is expected to be more than
sufficient for strong to severe storms (both ~45 knots). The
limiting factor will be the instability. Nevertheless, MUCAPE
~750-1000 J/kg will be sufficient for elevated storms that could
produce hail. A stable boundary layer should mitigate the wind
threat, but with a rather intense low-level jet (>50 knots), some
higher momentum air/gusty winds could make it to the surface
within some downdrafts. Any rain chances should end Monday
morning across southeast Oklahoma.

For Tuesday through Thursday, relatively quiet weather is expected.
Embedded short-waves that will rotate around a cut-off mid/upper
level low across the Northern Plains will allow for reinforcing
shots of cold air to affect the Southern Plains.

For late Friday into Saturday, a mid/upper level low is forecast to
cut off across the southwest United States/northern Mexico.
Impacts will be modulated by the eventual location of the cut-
off low as the 27/00Z ECMWF is farther west than the 27/00Z GFS
with the system. Consequently, the GFS places Oklahoma and western
north Texas within a region of isentropic ascent late Friday into
Saturday. In contrast, the ECMWF holds off precip until late
Saturday into Sunday.

Impacts will also be modulated by the eventual temperature
profile. Overall, the GFS is cooler than the ECMWF (owing to the
GFS keeping a mid-level trough across the Northern Plains while
the ECMWF develops a ridge). For Saturday morning, GFS BUFR
soundings across northwest Oklahoma indicate that snow will be
possible if precipitation occurs. In this type of synoptic setup
(i.e., isentropic ascent/warm air advection), would anticipate a
mixture of precipitation types. However, for now, will just
include low chances of rain and rain/snow mixture to simplify the
forecast as the eventual transition zones will evolve as the
(possible) event draws closer. Only low chances were included
because of uncertainty as suggested by the drier/warmer ECMWF
solution.

Mahale

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  62  50  65  37 /  60  30  10   0
Hobart OK         64  43  63  36 /  60  20   0   0
Wichita Falls TX  66  51  67  43 /  30  30  10   0
Gage OK           67  37  62  29 /  60  10   0   0
Ponca City OK     61  48  64  34 /  60  30  10   0
Durant OK         62  57  69  44 /  30  80  40   0

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Wind Advisory from 10 AM this morning to 6 PM CST this evening
     for OKZ004>007-009>012-014>017-021-022-033>036.

TX...Wind Advisory from 10 AM this morning to 6 PM CST this evening
     for TXZ083>085-087-088.

&&

$$

25/10/10



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