Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 171253

Area Forecast Discussion
National Weather Service Norman OK
753 AM CDT Sun Sep 17 2017



Just sent a minor update to follow radar trends. The forecast
remains in good shape. Convective coverage has increased across
portions of central Oklahoma into northeast Oklahoma over the
last hour or two where subtle moistening in mid levels was seen in
12z OUN sounding. We confined higher probabilities to generally
east of a line from Stillwater to OKC to Holdenville through mid-
morning, aligned with enhanced mid-level moisture in models.
Parcels seem to be originating around 800-700 mb yielding modest
instability (~750 J/kg MUCAPE). Overall weak convection and lack
of boundary layer mixing/momentum transfer potential will limit
strong/severe potential this morning. Also adjusted winds based on
latest obs and short term guidance for a slightly further south
frontal position.



.PREV DISCUSSION... /issued 717 AM CDT Sun Sep 17 2017/

..Aviation Discussion...

For the 12z TAFs:

Isolated to scattered convection has increased over the last
couple of hours from central Oklahoma into southwest Oklahoma. A
few lightning strikes have been observed just north of OKC, but
just outside of the 10 nm ring, and direct impact to either OKC
by these storms is not expected. Weaker convection without any
observed lightning yet is occurring near Lawton up to Chickasha.
Vicinity showers were included at other TAF sites this morning.
20-40 percent coverage of convection is expected to continue
through the day with northern TAF sites having the greatest chance
of being impacted, particularly PNC. Otherwise generally light
winds and VFR conditions are expected.

PREV DISCUSSION... /issued 333 AM CDT Sun Sep 17 2017/

Main concerns will be rain chances next couple of days, the hot
temperatures/associated elevated fire weather concerns and finally
development of western trough and its impacts on the southern
Plains by the end of the forecast period.

Weak surface cold front will continue to push slowly south this
morning, before retreating back north late today and tonight.
Widely scattered showers and thunderstorms will remain possible
during the day today. Expect to see an increase in activity
tonight as a wave moves out of the Rockies into the plains,
convection should develop. Highest chances remain across northern
half of Oklahoma. Instability should be sufficient for a few
strong storms.

Still appears that we will see an overall lull in the rain/storm
chances for much of the work week as any large scale forcing is
lacking. However, some isolated activity remains possible nearly
everyday as tropical fetch remains. Best chance would appear to be
late Wednesday into Wednesday night as a cold front pushes south
into the area, however warm mid-level temps may limit our chances
even then.

Our attention then turns to large western trough that takes shape
by the end of the week. The more recent model runs want to
develop a closed low. However, the 00Z run of the GFS does keep
the system open and a bit more progressive compared to the ECMWF,
which keeps the closed low scenario. Have continued to trend
precip chances higher for next weekend, especially across the
west, but confidence is not high enough, because of model
differences, to go more than high chance category.


Oklahoma City OK  88  69  90  71 /  50  30  20  10
Hobart OK         91  67  92  70 /  30  30  10  20
Wichita Falls TX  95  70  94  72 /  20  20  10  10
Gage OK           78  64  91  67 /  40  40  10  20
Ponca City OK     83  68  88  69 /  40  50  40  20
Durant OK         91  70  92  71 /  10  10  10   0




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