Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 240036 AAA
AFDOUN

Area Forecast Discussion...UPDATED
National Weather Service Norman OK
636 PM CST Fri Feb 23 2018

.UPDATE...
Temperatures in some locations are already lower than forecasted
lows for those areas so made some adjustments to account for it
but overall temperatures are expected to remain fairly steady
overnight. Patchy fog will be possible this evening and overnight
so have added a mention in the forecast. Some of the fog may
become dense but will hold off on a dense fog advisory for now and
continue to monitor observations/reports.

&&

.PREV DISCUSSION... /issued 448 PM CST Fri Feb 23 2018/

AVIATION...
Very moist boundary layer will maintain IFR/LIFR conditions
through the night into the morning hours on Saturday along with
widespread drizzle. A storm system will bring a round of
thunderstorms that will impact many of the TAF sites between
12Z & 18Z Saturday before drier air works in behind
dryline/Pacific front. This should bring in VFR conditions during
the latter part of the forecast period.

PREV DISCUSSION... /issued 324 PM CST Fri Feb 23 2018/

DISCUSSION...
Primary forecast focus is on the next 24 to 48 hours, with moderate
to heavy rainfall concerns, strong to severe convection, and fire
weather concerns through Saturday.

This afternoon and evening, scattered showers and isolated thunder
will remain possible across a large portion of central Oklahoma and
north Texas. Forcing for ascent continues to be provided by a weak
500mb shortwave and the resulting broad isentropic ascent spread
across the region. The larger western trough continues to churn
eastward, still just west of the Four Corners through 21Z (3 PM).
The greatest rainfall amounts remain confined to southeastern
Oklahoma into north Texas, where amounts of a half inch to just over
an inch have occured through today.

There will be a lull in moderate precipitation overnight, as the
weak short wave lifts east/northeast. However, it will remain damp,
with drizzle and light rain chances continuing across most of the
region, along with some scattered showers across southeastern
Oklahoma. Through sunrise, Saturday, thunderstorm chances will
increase, as the larger 500mb trough begins it`s swing across the
Rockies, with another broad area of forcing for ascent focused
across north Texas into eastern Oklahoma and up onto the Ozark
Plateau. Short to mid range guidance remains in good agreement along
with coordination between neighboring offices and WPC. Increased
rainfall amounts across southwestern and south central Oklahoma into
north Texas, expanding the Flood Watch an extra row of counties
west, which was done earlier this morning. Rainfall chances will be
the greatest Saturday morning across southwestern Oklahoma.
Additional rainfall amounts, including tonight, but more so focused
Saturday morning, will approach 1 to 2 inches, widespread within the
watch area, with locally higher amounts possible.

With between 4 to 6 inches earlier this week, an additional 1 or so
inches today, and more on the way overnight and Saturday, soils are
basically hydrophobic, completely saturated. Flash flooding is
possible, especially within the hilly terrain of south central and
southeastern Oklahoma as thunderstorms increase in coverage Saturday
Morning.

Additionally, elevated instability, between 750 and 1500 J/Kg
possible, and effective shear of 30 to 40 kts, severe hail and wind
may accompany storms Saturday morning in southeastern Oklahoma. This
will be especially true, if storms develop into a line, as many of
the CAMs and conditions suggest. Most likely time for strong
to severe storms would be in dawn hours through the morning.

Not to be outdone, elevated to near critical fire weather conditions
will develop Saturday afternoon, as southwest winds increase and
temperatures warm into the mid 60s. Although ERC-G values are down
due to the recent precipitation, given the drought conditions, it
won`t take much for fuels to dry out.

For Sunday and Monday, dry and mild conditions are expected to
persist, with highs in the 50s and 60s each day. elevated to near
critical fire weather conditions will exist, as well, across western
Oklahoma and western north Texas. West and southwest winds will be
breezy on Sunday, as a weak surface trough swings across the region.
Monday, south winds will increase in the afternoon as the surface
pressure gradient increases across the Panhandles into western
Oklahoma.

For Tuesday, shower and thunderstorm chances will increase, more
likely in the afternoon, boundary layer return flow becomes
established and dew points climb back into the 50s across Texoma by
mid afternoon. Once again, focus will be provided by a swath of
isentropic ascent supported by a surface trough ahead of a digging
500mb trough across southern California and Arizona. Beyond Tuesday
night, long range guidance begins to diverge considerably with the
synoptic pattern. However, there remains enough continuity to lend
confidence to shower and thunderstorm chances continuing through
Wednesday into early Thursday, primarily across the eastern half of
Oklahoma.

Fire weather concerns are increased on Wednesday, but hang
on how the swing of the 500mb trough will unfold. Either way, it
appears with the push of the surface front east, it will open up
strong southwesterly winds to western north Texas and southwestern
Oklahoma.

Kurtz

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  37  59  31  62 /  40  70   0   0
Hobart OK         35  62  29  62 /  30  30   0   0
Wichita Falls TX  37  66  33  66 /  40  70   0   0
Gage OK           32  53  24  57 /  20  10   0   0
Ponca City OK     35  51  26  58 /  50  50   0   0
Durant OK         44  63  37  65 /  80  90   0   0

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Flood Watch through Saturday afternoon for OKZ032-041>043-
     045>048-050>052.

TX...Flood Watch through Saturday afternoon for TXZ090.

&&

$$

25/30


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