Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 170524
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
1124 PM CST Sat Dec 16 2017

...Aviation Discussion...

&&

.AVIATION...
For the 06z TAFs:
Drizzle should diminish early tonight at OKC/OUN but light fog may
persist into the early morning. MVFR to IFR ceilings will persist
and possibly lower to LIFR at some sites later tonight. All sites
should improve to MVFR later in the morning. Lower ceilings and
possibly fog will be possible toward the end of the TAF period
again.

&&

.PREV DISCUSSION... /issued 721 PM CST Sat Dec 16 2017/

..Updated...

DISCUSSION...
The forecast is in good shape and only minor adjustments were
made. Based on latest trends, we adjusted precipitation
probabilities. This included starting higher probabilities a
little quicker across much of the area and moving the rain out a
little faster later tonight. Also, we have added higher wind gusts
for this evening. Grids and graphics have been sent.

BRB

PREV DISCUSSION... /issued 522 PM CST Sat Dec 16 2017/

AVIATION...
VFR conditions will quickly become MVFR this evening with area of
light rain expected to move south to north across the area.
Ceilings may drop into IFR category late tonight and linger
through mid-morning before gradually improving through the day.
VFR conditions may return across west/southwest late in the day
Sunday, with sites farther east remaining MVFR throughout the
forecast period. Gusty south winds will weaken overnight and weak
front will shift winds at GAG/WWR to the northwest by midday.

PREV DISCUSSION... /issued 344 PM CST Sat Dec 16 2017/

DISCUSSION...
A closed-low, currently across southwest Texas, will open and
eject northeastward tonight. GOES-16 Water Vapor Imagery indicates
a stream of moisture advecting northward, ahead of the low. Light
radar echoes have already begun to develop across north Texas as
ascent increases downstream from the wave.

The combination of ascent and moisture will be sufficient for
widespread rain across the eastern two-thirds of Oklahoma. It is a
scenario where probabilities for rainfall will be rather high,
even though most locations will receive low amounts. The highest
rainfall amounts are expected across southeast Oklahoma, where
~0.25" is expected. Amounts will decrease with northwest extent.
Rain should exit north central Oklahoma by 12Z.

For tomorrow, remnant cloud cover may create a northeast to
southwest temperature gradient across the area; cooler
temperatures are expected across north central Oklahoma with
warmer temperatures across southwest Oklahoma/north Texas.

Another closed low, similar to tonight`s, is expected to pass by
Tuesday into Tuesday night with widespread rain expected one
again. The highest chance for rain will be across
southern/southeastern Oklahoma. Isolated thunder can`t be ruled
out in far southeast Oklahoma with some elevated instability.
Temperatures will remain ~10F above average Monday through
Wednesday, with highs generally in the upper-50Fs to mid- 60Fs.

By Thursday, a shortwave trough will amplify and pass by the
Northern Plains. The attendant cold front will enter northwest
Oklahoma Thursday afternoon and move by the entire area Thursday
night. Ahead of the front, another warm day is expected with the
potential for Elevated to Near Critical fire weather conditions.
Behind this cold front, expect falling temperatures Thursday
afternoon across northwest Oklahoma. In the front`s wake, much
colder temperatures are expected Friday with high temperatures
only in the 30Fs.

There continues to be high uncertainty on the potential for
winter precipitation next weekend. The 16/12Z GFS is aggressive
with winter precipitation on Saturday as it closes off a low
across the southwest U.S.; however, it is important to note that
several GEFS members and the 16/12Z ECMWF are not as aggressive
with precipitation Saturday. The ECMWF does suggest a chance of
snow Saturday night into Sunday with a wave that approaches from
the northwest, but many of its ensembles are not as aggressive and
its source of ascent is different than the GFS`s (northern stream
wave vs. southern stream wave).

For now, will introduce only a low chance of snow Saturday across
western Oklahoma/north Texas because several ensemble members
are less aggressive than their deterministic counterpart. The
bottom line is much colder weather is expected late this week with
at least a low chance of winter precipitation next weekend--but
specifics are yet to be determined.

Mahale

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  59  42  52  34 /  10  70  10   0
Hobart OK         59  40  53  30 /  10  40   0   0
Wichita Falls TX  62  42  61  37 /  20  60   0   0
Gage OK           60  35  51  26 /   0  20   0   0
Ponca City OK     60  44  48  32 /   0  50  10   0
Durant OK         61  44  57  41 /  20 100  10   0

&&

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

$$

12/30



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