Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 190100 AAA
AFDOUN

Area Forecast Discussion...UPDATED
National Weather Service Norman OK
700 PM CST Sun Feb 18 2018

.UPDATE...
Allowed the Red Flag Warning and Wind Advisory expire at 6 pm
across parts of northwestern Oklahoma.

Added patchy fog and drizzle mention tonight near and east
of I-35. Added thunder mention tonight (mainly after midnight)
southeast of a Sayre to Enid to Blackwell line.

Other small adjustments to hourly elements (surface temperatures,
dewpoints, winds, and sky cover) were made as well.

&&

.DISCUSSION...
Fog/drizzle as well as thunderstorms are possible tonight.

Due to increasing surface humidity values and decreasing surface
winds, allowed the Red Flag Warning and Wind Advisory expire.
Note that there a rather large wildfire northeast of Freedom in
Woods county where surface winds will be slow to decrease tonight.

Latest surface observations have been depicting decreasing
ceilings and visibilities mainly east of a Ponca City to El Reno
to Waurika line with some drizzle and fog forming. Thus, added
this to the forecast. Overall, do not think widespread dense fog
(visibilities 1/4 mile or less) will form tonight due to the
strong surface winds. Also think surface visibilities will be
worst before midnight then improve after midnight as surface
winds, temperatures, and dewpoints increase.

Some models, particularly the HRRR, have been depicting that some
elevated showers and thunderstorms will form tonight and move
northeastward, affecting some areas mainly southeast of a Sayre
to Enid to Blackwell line between midnight and 6 am. This seems
reasonable. Severe storms seem unlikely due to marginal
instability (MUCAPE generally 500-1000 J/kg). However, a
few storms could be strong and produce small hail as well as
gusty winds. Kept rain chances generally in the 20-50% range to
account for this activity.

MBS

&&

.PREV DISCUSSION... /issued 550 PM CST Sun Feb 18 2018/

DISCUSSION...
Aviation discussion for the 00 UTC TAFs is below.

AVIATION...
Overall, many places (except KWWR and KGAG) will experience
worsening conditions now through 10 UTC, then an improving trend.

KOKC and KOUN (and possibly KPNC) will likely experience
conditions transitioning from IFR to LIFR by 03 UTC.
These conditions should improve sometime after 06 UTC, though
the exact timing of improvement remains uncertain.

MVFR/IFR conditions will likely form near KSPS, KLAW, KCSM, and
KHBR 03-10 UTC, though exact timing remains uncertain.

Conditions will improve to MVFR or VFR at all sites after 14 UTC
with locations in western and northwestern Oklahoma as well as
western north Texas having the highest chances for VFR conditions.

Added VCSH to some sites (KOKC, KOUN, KLAW, and KSPS) for about a
3 hour period 08-14 UTC due to moderate confidence of occurrence.
TS may be possible, but did mention due to lower confidence
of occurrence.

Non-convective low level wind shear is possible now through
15 UTC, but did not mention due to low confidence of occurrence.

MBS

PREV DISCUSSION... /issued 303 PM CST Sun Feb 18 2018/

DISCUSSION...
The amplification of a western trough and eastern ridge
will coincide with the transport of very moist air into
northern Texas and Oklahoma through Monday. By tonight/early
Monday, forecast PW`s will at or above the max moving
average (mid February) per SPC`s sounding climatology page.

Tonight into Monday, widely scattered light rain showers should
develop across at least the eastern half of Oklahoma with perhaps
better chances in south central and southeast Oklahoma.  A few
rumbles of thunder will also be possible which will result in
higher rainfall totals.

The wind will remain very breezy overnight with slightly lower
wind speeds across northern Oklahoma by Monday morning.

During the day Monday, a dryline will move across the western
third of Oklahoma and adjacent areas of western north Texas.
Mid to high clouds may limit the amount of mixing Monday
afternoon; however, breezy conditions and humidity approaching 25
percent may result in elevated, near-critical fire weather
conditions across far western Oklahoma and western north Texas.
Cloudy conditions with widely scattered showers are expected
across central and eastern Oklahoma.

Scattered to widespraed rain and embedded thunderstorms are
expected Monday night through Tuesday. Some of the rain may
be heavy at times, especially across south central and southeast
Oklahoma on Tuesday.

On Tuesday, much colder air will begin to move into at least
northern Oklahoma during the morning and early afternoon. The
surface front/wind shift should be south of our north Texas and
southeast Oklahoma counties by early to mid evening Tuesday. How
quickly the axis of heavy rain/rain moves into eastern Oklahoma
and Arkansas is somewhat uncertain at this time.

With rather cold air in place, some models forecast that mainly
light precipitation may develop Wednesday/Wednesday evening. The
precipitation would develop across northern Texas and southern
Oklahoma first and then spread northward through the day. Will
keep a chance of freezing rain perhaps sleet in the forecast,
at this time. Any ice or sleet accumulations will be light, but
perhaps enough to create some hazardous driving conditions.

Wednesday night into Thursday night may be mainly dry for most of
the area. By Thursday night into Friday another round of
precipitation may develop and move across most of Oklahoma and
northern Texas.

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  52  70  61  69 /  30  40  70  70
Hobart OK         60  77  56  71 /  20  20  40  30
Wichita Falls TX  59  77  62  75 /  30  30  60  60
Gage OK           53  75  49  59 /   0   0  10  10
Ponca City OK     53  70  60  63 /  30  40  70  70
Durant OK         52  68  64  68 /  40  50  70  90

&&

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

$$

17/17/17



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