Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 111739
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
1239 PM CDT Fri Aug 11 2017

.DISCUSSION...
The 18Z aviation discussion follows....

&&

.AVIATION...
The storm complex that passed across most of Oklahoma and part of
extreme north Texas last night has dissipated, except for a few
tiny showers south of KHBR. We expect no significant redevelopment
until overnight tonight. Patches of low ceilings remain in the
moist lower levels of the atmosphere, and these should gradually
rise/dissipate as afternoon heating progresses.

It appears at this point that there will not be enough
instability or a significant focus for storm development this
afternoon, so chances of TSRA through about 12/0800Z are quite
low. However, model forecasts point to another storm complex
forming over the southern High Plains, and moving/expanding toward
the east overnight. Most of our TAF sites are likely to be
affected by this complex (all but KSPS). Confidence in timing and
exact location is fairly low, but we are more confident that
there will be a complex...and that it will affect some part of
central and western Oklahoma tomorrow morning.

CmS/26
&&

.PREV DISCUSSION... /issued 1045 AM CDT Fri Aug 11 2017/

UPDATE...
Overhauled POPs and adjusted trends in clouds, temperatures.

DISCUSSION...
The remnant convection has decreased in coverage and intensity
through the morning, but is persisting in the short term. Will
keep likely POPs (but areal coverage wording) in the axis across
southern Oklahoma, but this should still diminish through the
morning.

PREV DISCUSSION... /issued 555 AM CDT Fri Aug 11 2017/

AVIATION...11/12Z TAF ISSUANCE...
Primary aviation concern is on going convection across portions of
central and southern/western Oklahoma. Many TAF sites are out of
the expected path/coverage of remaining thunderstorms, including
KOKC. Attempted to keep the TAFs simple, with the evolving complex
of storms, this morning. Overall, most sites are now VFR or close
to it, with, primarily, winds out of the north, breezy at times.
Expect the ongoing convection to persist through mid to late
morning, continuing to push eastward. Overnight, TSRA chances
return, as another complex is expected to move across the region.
At this time, only confidence for a mention in the TAFs was at
KGAG and KWWR, in the northwest.

Kurtz

PREV DISCUSSION... /issued 135 AM CDT Fri Aug 11 2017/

DISCUSSION...
Primary forecast focus is on this morning`s convection, along with
today and another complex tonight into Saturday.

This morning through sunrise, a loosely organized area of convection
will continue to move eastward across the northern half of Oklahoma.
A persistent MCV can be visualized on KVNX and surface observations,
in northwestern Oklahoma. The low level jet has continued to to
steadily increase ahead of this feature and convection will continue
to be supported by a fairly stout 500mb short wave moving eastward
off the western high plains of Colorado.

11/00z sounding from KOUN measured a pwat of 1.87 in, and KAMA, 1.36
in, both of which are above the 90th percentile. Nearest the MCV,
broad ascent coupled with MUCAPEs around 1000-1500 J/Kg, strong
updrafts will lead to efficient rain producing storms. In just over
an hour, Slapout, OK between, 10:15 pm and 11:15 pm, picked up 2.91
inches. This is concerning, leading to increased confidence that a
localized flash flooding threat will persist through the remainder
of the overnight hours into the morning. The heaviest rainfall from
Thursday occured over west central Oklahoma, from Kingfisher County
through Grady county. Most flash flood guidance would suggest, 2.50
to 3.00 in/hr for the lower threshold for Flash Flood Warning
issuance, if needed.

Felt it was necessary to issue a Flood Watch for flash flooding,
beginning this morning and continuing through Sunday morning. More
details to follow, but with several rounds of rainfall expected due
to overnight thunderstorm complexes, multi-day rainfall amounts of 3
to 5 inches are possible across much of central and western
Oklahoma, with locally higher amounts more than possible through
Sunday Morning.

Forward propagation vectors of around 20kts, suggest a fairly
progressive system, given similar 0-3km bulk shear values.
Therefore, concerns for backbuilding are not all that high.
Efficiency will be the primary driver for locally heavy rainfall.
Earlier, around 1030 pm, Slapout recorded a 58 mph gust. Given
instability over 1000 J/Kg and areas of 0-6km shear around 30 to 40
kts, instances of severe gusts, over 60 mph, and up to Half dollar
sized hail will remain a possibility overnight.

After sunrise, expect lingering showers and thunderstorms,
scattered, across portions of northern and central Oklahoma, with
the remaining complex continuing across eastern Oklahoma, possibly
nearer the KS/OK border. Expect any stronger storms to be well east
of the I-35 corridor. Precipitation chances will dwindle through the
late morning and through the afternoon, but with remnant outflow
boundaries and lingering instability, will keep low precip chances
for much of the region through the afternoon, with the best
potential for scattered development across central to south central
Oklahoma, near the Red River, where a surface boundary may stall
through late this afternoon.

As most are aware by now, we`re stuck under a persistent pattern,
with a trend of nightly MCSs/complexes of some sort, near daily into
early next week. Convection will likely be ongoing over the high
terrain of Colorado/New Mexico and the Panhandles by late
afternoon/evening, this activity will persist moving steadily
eastward into the overnight. Looking at MCS maintenance parameters,
it`s likely this activity will build east/southeast across western
Oklahoma into central Oklahoma through sunrise, Saturday. The wet
trend continues into Sunday, with another complex moving across the
region Saturday night into Sunday. As mentioned above, a Flood Watch
for flash flooding remains in effect through early Sunday morning.

Stay Safe!

Kurtz

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  85  70  81  70 /  40  40  70  70
Hobart OK         90  72  85  71 /  60  50  60  70
Wichita Falls TX  95  76  93  73 /  30  20  50  50
Gage OK           80  68  78  66 /  20  70  70  70
Ponca City OK     84  68  80  68 /  20  20  50  60
Durant OK         93  74  88  74 /  50  20  50  70

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Flood Watch through Sunday morning for OKZ004>048-050>052.

TX...None.
&&

$$

26/23/23



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