Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 190448

Area Forecast Discussion
National Weather Service Norman OK
1148 PM CDT Sun Jun 18 2017

The 06Z aviation discussion follows....


Elevated instability above a relatively cool airmass has led to
the development of scattered showers over parts of south-central
Oklahoma. These showers may affect KLAW and KSPS through 12Z (and
there could be a few TSRA near KSPS during that time).
Thunderstorms should be confined to the Red River area and
southward by morning, and will continue to sink south through the
morning. Low ceilings (low MVFR, possibly high IFR categories) are
also expected to persist near the Red River well into Monday
morning, before finally rising above 3,000 ft by 18Z. VFR
conditions are expected throughout Oklahoma and north Texas after
18Z Monday, and winds will mostly be light east or southeast,
possibly increasing a bit in speed in western Oklahoma Monday
afternoon, as the area of cool high pressure begins to retreat to
the east.


.PREV DISCUSSION... /issued 736 PM CDT Sun Jun 18 2017/

Increased rain chances this evening across parts of central
and southeastern Oklahoma. Made minor changes tonight mainly to
hourly sky cover and surface temperatures.

A few severe storms with large hail and damaging winds may occur
tonight mainly southeast of I-44. Locally heavy rainfall and
flash flooding are possible as well.

Latest radars indicated light echoes developing roughly near I-40
including the OKC metro area. These appear to be forming along the
850 mb front. Think this activity will grow upscale and move
south/southeast in the next few hours as the mid level cap around
700 mb weakens due to cold air advection at this level
(temperatures falling below +10C at this level). Latest HRRR
model runs support this solution with storms becoming more robust
and numerous somewhere near a Ada to McAlester line by 11 pm
this evening.

A few severe thunderstorms may occur tonight, mainly in the form
of large hail up to half dollar size as storms will be elevated in
nature, though not confident about this. The 00 UTC KOUN sounding
depicted MUCAPE of 1168 J/kg. MUCAPE values are generally
forecast to be 1000-3000 J/kg anywhere south of I-40 based on
latest RAP model analyses, but appears the cap will be too strong
for any storm development northwest of I-44. Current SPC Day 1
Convective Outlook handles this well. If enough storms could form,
there could be a few damaging wind gusts as well. Locally heavy
rainfall and flash flooding may be a bigger concern tonight with
precipitable water values 1.7-2.2", above the 90th percentile for
this of year, which will support rainfall rates of 1-4"/hr,
especially southeast of a Waurika to Pauls Valley to Shawnee line.

Products will be updated shortly.


PREV DISCUSSION... /issued 639 PM CDT Sun Jun 18 2017/

The 00Z aviation discussion follows....

A cold front now crossing Texas will be the source of lift later
this evening that will probably generate scattered showers and
thunderstorms near the Red River. Already, there is a line of
showers farther upstream along I-40, east of KSNL. As the front
continues to recede to the south, the convective activity is
expected to shift south into northern Texas, south of all our TAF
sites. A few areas of MVFR-level ceilings are likely near the Red
River this evening. Otherwise, expect VFR conditions and light
east/southeast winds overnight into Monday.


PREV DISCUSSION... /issued 227 PM CDT Sun Jun 18 2017/

Cold front still working its way across south-central and
southeast Oklahoma this afternoon. Chances for scattered to
numerous post=frontal storms will increase this evening and
especially overnight near and just north of this front, primarily
across south-central and southeast Oklahoma, as height falls and
associated erosion of mid-level cap occurs. Large hail will be
possible with steep lapse rates and 20 to 30 knots of shear. Heavy
rain could also become an issue near the Red River of southeast
Oklahoma where models are more persistent on storm formation.

Our cool down will not last long as temperatures expected to rise
to and above seasonal averages by Tuesday. With southwest U.S. upper
ridge attempting to build into Southern Plains ahead of next upper
trough, likely to see 100s again across western Oklahoma and
western north Texas by the end of the week.

Models beginning to show some consistency on frontal timing late
in the week with strong cold front potential late Friday and
Saturday. Still some question on amount/potential of tropical
moisture associated with Gulf system to interact with this front,
but given approaching high amplitude trough, tropical system will
likley be kicked eastward before it can get up this far north.
Regardless, next chance for organized rain and hopefully more
widespread activity appears on tap for the first part of next


Oklahoma City OK  62  87  66  92 /  20   0   0  10
Hobart OK         62  89  66  94 /  10   0   0  10
Wichita Falls TX  67  88  69  93 /  20  10  10  10
Gage OK           59  87  63  93 /   0   0   0  10
Ponca City OK     61  85  63  91 /   0   0   0  10
Durant OK         68  87  68  92 /  50  20  10  10




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