Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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438
FXUS64 KOUN 081737
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
1137 AM CST Thu Dec 8 2016

.DISCUSSION...
18Z TAFs.

&&

.AVIATION...
Although clouds will be widespread, especially in southern
Oklahoma and northern Texas, VFR ceilings are expected through the
forecast period. Winds will become light this evening and
overnight as the surface ridge moves through, then increase from
the south on Monday morning.

&&

.PREV DISCUSSION... /issued 1054 AM CST Thu Dec 8 2016/

UPDATE...
Updated cloud cover through 00Z.

DISCUSSION...
Opted to increase cloud cover across southern Oklahoma/western
north Texas this afternoon. Otherwise, no significant changes
were needed to the forecast. Expect a cold day with high
temperatures in the 30s--around 20F below average for early
December.

Mahale

PREV DISCUSSION... /issued 511 AM CST Thu Dec 8 2016/

DISCUSSION...

AVIATION... /For the 12z TAFs/
VFR conditions have returned and will persist through the TAF
period. Northerly post-frontal winds are still 12 knots or higher
at TAF sites across southern Oklahoma and western north Texas, but
these should gradually subside and become light later this
afternoon. Surface high pressure will move across the area early
tomorrow morning causing a gradual veering of winds to
southeasterly by the end of the TAF period.

PREV DISCUSSION... /issued 335 AM CST Thu Dec 8 2016/

DISCUSSION...
An air mass of Arctic origins has arrived. Early this morning
temperatures continued to fall with all locations now below
freezing and a few locations in northwest Oklahoma already in the
mid teens. Low stratus was diminishing but mid and high clouds
remained over the area, but should slowly decrease throughout the
day.

No significant weather impacts are expected over the next
several days. A progressive upper flow pattern with occasional low
amplitude waves will continue into the middle of next week. This
will lead to variations in temperatures but generally dry
conditions. The models vary with strength and timing of these
waves leading to a low confidence forecast, especially early next
week. The first wave will result in modest mid-level height falls
and enhanced southerly moist low level flow Saturday. By Saturday
night models show saturated low levels that may be sufficient for
drizzle across roughly the southeast quarter of the area. This may
persist across the southeast and far east through the first half
of Sunday. Model forecast soundings show this shallow (but
sufficiently deep saturated layer for drizzle) beneath a very
pronounced warm dry layer consequence of strongly
veering/strengthening lower level winds (differential advection
scenario). This conceptually fits these progressive flow patterns
and typically limits our precipitation. Measurable amounts are in
question, and should be limited to a couple hundreths at best.

For the rest of the forecast we did not deviate much from a
blended or consensus approach given large differences in how the
models handle the cold front on Tuesday. There are significant run
to run inconsistencies and a large spread in the ensembles. GFS is
the deepest/fastest with the approaching deep trough which forces
a more robust cold surge into the area sooner. Adjustments to
temperatures either up or down may be significant once the medium
range guidance comes into better agreement or at least shows some
meaningful trends. One change we did make was to increase winds on
Tuesday given the tendency for initialization blend to not capture
these post frontal wind events very well, and sense with just
about any solution a cold front moves in at some point during the
day.

BRB

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  33  14  40  27 /   0   0   0   0
Hobart OK         33  18  39  27 /   0   0   0   0
Wichita Falls TX  35  19  41  29 /   0   0   0   0
Gage OK           29  13  40  25 /   0   0   0   0
Ponca City OK     31  11  37  25 /   0   0   0   0
Durant OK         39  20  44  30 /   0   0   0   0

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&

$$



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