Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 261154 AAA
AFDOUN

Area Forecast Discussion...UPDATED
National Weather Service Norman OK
554 AM CST Sun Feb 26 2017

.AVIATION...26/12z TAF Issuance...
Broken to scattered mid-level stratus will continue to stream
across most of the region through the morning hours. South and
southeasterly winds will persist, weakening in the evening,
becoming more west and northwestward by the late afternoon.
Overnight, as a weak surface front slides south and southeast,
winds will shift to the north and east. MVFR ceilings are expected
to develop tonight, primarily across central into southern
Oklahoma and into north Texas.

Kurtz

&&

.PREV DISCUSSION... /issued 501 AM CST Sun Feb 26 2017/

DISCUSSION...
Primary forecast focus is on Tuesday, with Critical fire weather
conditions in the west and a marginal risk of severe storms in the
east/southeast.

This morning, south winds have picked up slightly from north Texas
into southern Oklahoma. Farther north, scattered midlevel clouds
continue to stream along the Oklahoma/Kansas border, with light snow
bands north and northeast of Wichita. Chilly temperatures this
morning will rebound through the day, as warm air advection
increases across the region ahead of an approaching surface trough.
Afternoon highs will top out in the mid 50s to mid 60s.

Through the afternoon into the evening, low level return flow ahead
of the approaching open 500mb trough off the western high plains,
will result in gradually increasing surface dew points and low level
moisture. In response, shower and thunderstorm chances will increase
across east Texas into southeastern Oklahoma by the evening. The
greatest chances will be focused along a decent axis of isentropic
ascent, influenced by the upper level support of the broad 500mb
short wave trough as it swings across Oklahoma towards the Ouachitas
and up the Ozark Plateau, overnight. Scattered rain/thunder chances
will linger across the eastern half of Oklahoma, through the day,
ending by the evening.

Tuesday...Critical Fire Weather...Marginal Risk of Storms...
A stronger 500mb trough will be making its way across the western
United States, with a fairly stout surface trough developing into
the morning hours, stretched from the northern Plains back to the
Panhandles into northeastern New Mexico. This will result in a
complex scenario, with warm dry advection in the west and warm
moist advection in the east, close to a classic fire weather
pattern.

For western north Texas and west/southwest Oklahoma, southwesterly
flow will dominate, with the 850mb jet approaching 50kts through the
afternoon. A stout 700/850mb thermal gradient will set up from the
Edwards Plateau, along and off the Llano Estacado and towards/along
the I-35 corridor in central and northern Oklahoma. Model blends
continue to struggle with temperatures, winds, and dew points. Upped
the winds considerably across western Oklahoma into western north
Texas, MOS guidance has provided a decent starting point. Sustained
winds through the afternoon will range from 20 to 25 mph, while
gusts will push 35 mph. At the same time, leaned on traditional
guidance from the GFS/ECMWF/NAM for dew points, as they resolve the
gradient/dry line well. Once again, MOS guidance was a good starting
point for temperatures, highs will be well into the 70s, pushing 80
in central Oklahoma to the mid 80s across western north Texas.
Suffice it to say, Critical fire weather conditions are expected to
develop from western north Texas and across western Oklahoma.

To the east, ahead of the dry line, warm moist return flow from the
gulf will persist, with dew points in the 50s by sunrise, pushing
the low 60s by mid to late morning into the afternoon. With forcing
for ascent from the dry line and decent instability, SBCAPE between
1000 and 1500 J/Kg, thunderstorms are expected to develop in the
late afternoon into the evening across southeastern Oklahoma, east
of I-35 and south of I-40, to start. Overall, instability will be
elevated, with hail and winds the major concern, especially given
forecast soundings reveal relatively high LCLs, between 3 and 5 KFt.
There is some reservations with this scenario as well. The same
forecast soundings suggest a cirrus and stratus coverage may persist
through the afternoon, which would impact instability development.
With that said, effective deep layer shear is stout, suggesting
severe hail development remains possible with the strongest
updrafts. Additionally, orientation would suggest a initial storms
would quickly merge into a broken line as they move eastward through
the evening. The SPC acknowledges the tricky/messy setup, with a
marginal risk of severe storms for areas south of I-40 and east of I-
35 and as far east as Atoka county. Hail will be the primary
concern, especially given elevated instability and shear.

By sunrise, Wednesday, a cold front will have pushed southward, well
beyond the Red River, with storm chances well east and southeast of
the area. Northerly flow will bring much cooler temperatures as
well. Locations in northwestern Oklahoma will see quite a stark
change, with highs Tuesday near 75 and lows Wednesday morning near
or at freezing. After Critical fire weather conditions, Tuesday, the
wind shift and then gusty north winds during the day, Wednesday, may
impact any containment efforts under way from previous fires.
Additionally, the dry and breezy conditions will result in elevated
fire weather conditions through the day.

Beyond Wednesday, dry conditions will persist into the weekend, with
elevated fire weather conditions both Thursday and Friday, due to
warm, dry, and breezy conditions each afternoon.

Kurtz

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  59  43  67  49 /   0  10  20  10
Hobart OK         59  40  68  45 /   0  10  10   0
Wichita Falls TX  65  47  73  51 /   0  20  10  10
Gage OK           54  32  69  43 /   0  10  10   0
Ponca City OK     56  37  62  47 /  10  10  20  10
Durant OK         60  48  71  57 /  20  50  30  10

&&

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

$$

03/04



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