Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 011017

Area Forecast Discussion
National Weather Service Norman OK
417 AM CST Thu Dec 1 2016

The primary forecast concerns continue to be the chance/type of
precipitation for Saturday and then impacts from a significantly
colder airmass by next Wednesday.

For today, a return to southerly winds will allow for a
seasonably warm day with temperatures in the mid-50s to low 60s
across the area with plenty of sunshine.

By late Friday into Saturday, increasing isentropic ascent/warm
air advection will result in widespread rain. The greatest ascent
will begin across parts of western north Texas Friday afternoon
and spread northeastward Friday night into Saturday. Rain chances
will increase with southward extent during the day Saturday.
Expect a cold rain for most locations with temperatures in the 40s
because of minimal insolation.

Some wet snow will still be possible across northwest Oklahoma
Friday night into early Saturday. Deterministic models
(GFS/ECMWF/NAM) still suggest surface and wetbulb temperatures
will be above freezing with the onset of precipitation. Therefore,
impacts for snow are still expected to be minimal because any
subfreezing temperatures are expected to quickly wetbulb to above

Most rain should shift eastward by Saturday night with a lull in
precipitation expected for most locations on Sunday. The upper-
level low is expected to lift northeastward on Monday, which will
increase the chance of rain--especially across central/southern
Oklahoma. Added a mention of isolated thunder across southeast
Oklahoma as there is evidence of some elevated instability. Expect
dry conditions in the low`s wake for Tuesday.

For Wednesday, the 01/00Z GFS and ECMWF are fairly consistent with
timing of the cold front. Still appears the airmass behind the
front will be well below average. Both models suggest an early
frontal passage. The end result, temperatures will likely be
falling through the day with gusty northerly winds behind the cold
front. Trended temperatures significantly colder than blended
guidance to account for a potentially tight temperature gradient.
Also increased wind speeds substantially behind the front as
models tend to underestimate wind speeds in strong cold air
advection regimes. Consequently, wind chill values could drop into
the teens behind the front-- especially across the northwest--
Wednesday afternoon.

There is more uncertainty with precipitation chances. Both models
indicate subtle ascent sufficient for light precipitation;
however, the location of the greatest ascent is unclear (the GFS
is farther south than the ECMWF). For now, kept a chance of snow
across the north transitioning to rain across the south. Bottom
line is the coldest air of the season is likely Wednesday;
however, precipitation chances are less certain at this time.



Oklahoma City OK  59  34  56  42 /   0   0  20  60
Hobart OK         58  32  54  41 /   0   0  40  70
Wichita Falls TX  61  40  57  44 /   0   0  40  70
Gage OK           52  26  51  34 /   0   0  20  60
Ponca City OK     56  32  55  38 /   0   0  10  50
Durant OK         62  40  59  44 /   0   0  10  70




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