Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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000
FXUS64 KOUN 141705
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
1205 PM CDT Sat Oct 14 2017

.AVIATION...
Not much change from prev forecast. Gusty south/southwest winds will
continue through the day before relaxing around sunset. Strong cold
front will bring a period of storms to most sites this evening and
overnight. Ceilings and visibilities should remain VFR, however a
very brief period of MVFR conditions possible with the storms.
Strong north winds will also accompany the front with gusts of 35kts
to 40kts likely for a few hours before relaxing.

30

&&


.PREV DISCUSSION... /ISSUED 548 AM CDT Sat Oct 14 2017/

.DISCUSSION...
Aviation discussion for the 12 UTC TAFs is below.

&&

.AVIATION...
Overall, VFR conditions are expected to continue.

AMD NOT SKED was added to the KWWR TAF due to missing surface
observations.

Removed VCSH mention at KWWR and KGAG before 00 UTC as it appears
any -SHRA will stay north of these sites. Went with a VCTS mention
at KWWR 01-03 UTC with cold front passage.

South to southwest surface winds will become gusty at all sites by
16 UTC.

A strong cold front will move through Oklahoma and north Texas
00-12 UTC, bringing strong and gusty north surface winds along
with a band of SHRA/TSRA. Generally think VFR conditions will
occur with any SHRA/TSRA though brief MVFR/IFR conditions will be
possible. Surface wind gusts from the north from the SHRA/TSRA may
be near or just above 40 kt briefly.

MBS

&&

.PREV DISCUSSION... /issued 347 AM CDT Sat Oct 14 2017/

DISCUSSION...
The main challenges of the day are dealing with rain chances and
strong to severe storms today and tonight.

The biggest change to the previous forecast was to increase rain
chances tonight based on latest model guidance, particularly
latest HRRRX/ARW/NMM model runs.

Today, unseasonably warm/hot, humid, and breezy conditions will
occur across the area. Used a blend of guidance highs mainly in
the 80s to lower 90s, about 15 degrees above average for this time
of year. Today`s record highs (93 at Oklahoma City, 98 at Wichita
Falls, and 97 at Lawton) should not be reached. Daily warmest low
records will likely not occur (70 at Oklahoma City, 69 at Wichita
Falls, and 67 at Lawton) as well due to cooler air moving in this
evening with the cold front/rain/storms. South to southwesterly s
surface winds will be stronger today compared to yesterday in
many areas with gusts generally 15-30 mph by afternoon.

Kept 20-50% rain chances today mainly across northern Oklahoma,
north of a Cheyenne to Enid to Blackwell line where mid level
moisture convergence will allow for scattered showers and perhaps
a few weak storms through late this afternoon. Any rainfall should
remain light and mainly under 0.25" before 4 pm today.

Late this afternoon into tonight, showers and storms will grow in
coverage near the cold front as the cap erodes. Most short term
model guidance has been suggesting that robust storms will not
form until after 6 pm and perhaps as late as 8 pm near the cold
front, somewhere across northern Oklahoma. First storms have the
highest potential for producing severe hail due to sufficient
shear (0-6 km bulk shear 40-60 kt to support a mix of supercells
and multicells) and instability (MLCAPE 1500-3000 J/kg), which
should not be too large in size due to unseasonably high wetbulb
zero heights generally 11-12kft AGL. As mid level temperatures
quickly cool this evening with the approach of a mid/upper trough,
a line of storms will rapidly form near the front and quickly
move southward, producing widespread wind gusts 35-50 mph. A few
gusts may be 60-70 mph, which the latest SPC Day 1 Convective
Outlook Marginal Risk handles this well. This line will likely
weaken after 10 pm as it moves into southern Oklahoma and north
Texas where instability will be lower (MLCAPE 500-1500 J/kg).
Widespread rainfall will likely result across Oklahoma and north
Texas with rainfall amounts generally between 0.25" and 1".

Will not issue a Wind Advisory at this time for tonight. Strongest
wind gusts will likely be caused by the line of storms with gusts
40-50 mph which will be handled by Significant Weather Advisories
and/or Severe Thunderstorm Warnings for gusts 60-70 mph. Gradient
surface winds away from rain/storms may be quite strong due to
strong MSLP rises, but not sure this will occur as the boundary
layer may be stabilized from the rains which would decrease the
wind potential away from storms.

Cooler air will move into the area tonight. Went towards the
cooler side of guidance lows ranging from the lower 40s in
northwestern Oklahoma to the mid 50s in southeastern Oklahoma.

Sunday will become mostly sunny, much drier, and much cooler. A
few showers and some mid level clouds may linger near Atoka and
Durant before 10 am. Surface winds will slowly weaken through the
day. Model guidance highs mainly in the 60s appeared reasonable.

Sunday night into Monday morning, clear, cool, and rather calm
conditions are expected with below average temperatures. Some
patchy frost may occur across mainly northern Oklahoma, though
confidence of frost formation may be decreasing slightly based on
slightly warmer low levels from latest models. Regardless,
forecast lows in the mid 30s to mid 40s seemed reasonable.

Monday afternoon through Friday, dry weather and a gradual warm up
are forecast with southerly surface winds returning to the area.

MBS

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  89  50  64  40 /   0 100   0   0
Hobart OK         89  49  65  38 /  10  80   0   0
Wichita Falls TX  90  54  67  41 /   0 100  10   0
Gage OK           85  42  65  34 /  30  40   0   0
Ponca City OK     90  45  64  35 /  30 100   0   0
Durant OK         90  54  68  44 /   0 100  20   0

&&

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

$$

26/17/17



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