Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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000
FXUS64 KOUN 130326
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
926 PM CST Thu Jan 12 2017

.DISCUSSION...
So far this evening, conditions have been changing more or less
as previously forecast. The available short-range forecast models
show conditions very similar to what we`ve been seeing for the
last day or two from the NAM, which remains the most believable of
the models.

As a result, we do not plan to make any changes to the forecast
this evening.

&&

.PREV DISCUSSION... /issued 541 PM CST Thu Jan 12 2017/

DISCUSSION...
The 00Z aviation discussion follows....

AVIATION...
Freezing rain, mainly light, is expected to develop late this
evening over southeast Okalhoma, then spread slowly northwest with
time. Initially, the freezing rain will likely be in the form of
scattered small showers. As the day progresses tomorrow, the
freezing rain will probably become more widespread, but will
continue to be showery...and generally fairly light. Ceilings
will lower this evening from southeast to northwest across
Oklahoma/north Texas, and we expect little change in ceiling
heights through the day tomorrow, with most of the area barely
MVFR (as opposed to IFR). The boundary between rain and freezing
rain will lie roughly along a line from KSPS to KADH, perhaps a
little farther north early Friday.

CmS

PREV DISCUSSION... /issued 427 PM CST Thu Jan 12 2017/

DISCUSSION...
Around mid afternoon, temperatures ranged from the mid 30s across
northwestern Oklahoma to the lower 70s in far southeast parts
of the state. After sunset and overnight, temperatures will drop
below freezing north of a Shawnee to Lawton and Vernon, Texas
line and perhaps farther south.

As moisture increases above a shallow cold airmass, lower clouds
will develop and spread northward. NAM soundings suggest that by
midnight to 3 am...small convective showers may develop,
especially across the southern half of Oklahoma. Overall
confidence in this not high, but HRRR runs look somewhat
similar. Therefore, there is a risk of some light icing by
sunrise Friday, mainly within the Freezing Rain Advisory.

Weak isentropic ascent will continue through the day Friday
and this will result in mainly scattered areas of light freezing
rain and freezing drizzle. Mainly a cold rain is expected across
south central and southeast Oklahoma.

Although only light amounts of rain are expected during the day,
this may provide the best chance to create problem spots on roads,
especially bridges and overpasses.

Friday night into Saturday, isentropic lift will increase and
this will result in more widespread areas of freezing rain and
rain. This will also increase accumulations of ice on elevated
objects such as trees and power lines.

The temperature forecast and the risk of freezing rain and ice
becomes more uncertain during the day Saturday. The NAM was
followed closely for temperatures through Saturday night with a
slight decrease in temperatures across the northern half of
Oklahoma on Saturday. By late Saturday afternoon or early
evening, most areas along and south of Interstate 40 should be
above freezing. Farther north, freezing rain with embedded
thunderstorms should continue through at least early Sunday
morning. This will result in more ice accumulations and an
increased risk of power outages etc.

At this time, temperatures are expected to rise above freezing in
northern Oklahoma by at least Sunday afternoon.

A rather strong trough will move across west Texas and into the
central Plains Sunday into Monday. This will bring a period of
showers and thunderstorms, with a risk of heavy rainfall and
perhaps strong winds. There may be a risk of a few severe storms
across the southern part of the forecast area Sunday. We will try
and address this topic better in later forecast.

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  28  31  31  34 /  40  60  80  80
Hobart OK         28  30  30  32 /  30  50  70  80
Wichita Falls TX  33  34  33  37 /  40  60  70  70
Gage OK           23  27  27  31 /  10  30  60  80
Ponca City OK     26  30  29  31 /  20  70  70  80
Durant OK         38  45  38  43 /  40  60  70  60

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Ice Storm Warning from 6 AM Friday to 6 AM CST Sunday for
     OKZ004>020.

     Freezing Rain Advisory until 6 AM CST Saturday for OKZ037.

     Freezing Rain Advisory until 6 PM CST Saturday for OKZ021>030-
     033>036-038.

TX...Freezing Rain Advisory until 6 AM CST Saturday for TXZ083>085.

&&

$$

23/09



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