Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 041129

Area Forecast Discussion
National Weather Service Norman OK
529 AM CST Sun Dec 4 2016



.AVIATION... /For the 12z TAFs/
Gradually improving conditions are expected this morning. Rain is
exiting the area and some light drizzle may linger for another
couple of hours. IFR ceilings are occurring at a few locations,
but MVFR will become dominant through mid morning, followed by a
return to VFR. Northerly or northwesterly winds will remain light
and may become variable later tonight before turning southerly
toward the end of the TAF period.


.PREV DISCUSSION... /issued 352 AM CST Sun Dec 4 2016/

Latest radar mosaic and regional surface observations show low
stratus, drizzle, and areas of rain continuing tonight. The
heaviest hourly rainfall amounts have been just under a tenth of
an inch with a band of rain which has now reached Oklahoma City.
We have made adjustments to the short term forecast to better
refine space/time of this area of precipitation. Outside of this
area of rain, light to moderate drizzle has been effective at
providing measurable amounts (around a few hundreths of an inch).
Short term model guidance suggests that even after this area of
light-moderate rain moves out deep enough low level moisture may
linger for drizzle for a few more hours. This drizzle may even
linger for a short time after sunrise across the southeast portion
of the area. Gradual clearing will occur throughout the day as
the northern stream shortwave trough passes through the area.

Our attention then shifts to the deep closed low that has been
slowly drifting east over Mexico. All model guidance is in
agreement that this low will cross the Big Bend region of Texas
early Monday and accelerate northeastward as it opens up. A period
of increasing moisture and ascent will lead to some rain across
the southeast half of the area. Instability is absent in
soundings so thunderstorms are not expected.

A deepening broad trough extending across the northern Plains and
northern Rockies will force the first of two cold fronts into the
area Monday night bringing colder temperatures and low stratus to
the region on Tuesday. Meanwhile, the strengthening surface low
counterpart of the aforementioned system will move from Minnesota
into Canada and will help dislodge a very cold artic air mass.
This air mass will follow a second cold front forced south into
the area by an embedded shortwave that will move through the
central Rockies Tuesday night and onto the central Plains on
Wednesday. There are timing differences in the medium range
guidance. GFS remains faster than ECMWF by approximately 12 hours.
The strongest post-frontal surface pressure rises and resultant
winds will be with the second front. Wind speeds were increased
above the model blends behind both frontal passage, but especially
the second since it seems the timing differences between models is
causing speeds to be averaged down too much.

A period of ascent with the mid-upper shortwave trough may be
enough for some light snow late Tuesday into Wednesday across
mainly the northern portion of the area. GFS Bufkit forecast
soundings are not particularly robust with moisture and are fairly
dry in the low levels which will limit the snow potential and keep
amounts and any potential accumulation very light at most.

Temperatures are expected to fall into the teens across much of
the area Wednesday night and winds may stay strong enough for
single digit wind chill values, possible near zero in northern

Uncertainties exist late in the week with how quickly the artic
air mass will modify and/or shift east. GFS is quicker than ECMWF,
and is more progressive with another system moving in front the
west as well. Warmer temperatures are anticipated Saturday and
perhaps a few showers across mainly the southeast Saturday night
if enough moisture is present. Confidence at this range is low.



Oklahoma City OK  53  35  54  35 /  10   0  30  20
Hobart OK         53  34  53  33 /   0   0  20   0
Wichita Falls TX  55  40  52  37 /   0  10  50  10
Gage OK           52  31  57  27 /   0   0   0   0
Ponca City OK     53  32  56  32 /  20   0  20  20
Durant OK         53  41  50  39 /  20  20  70  40




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