Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 231523 AAA

Area Forecast Discussion...UPDATED
National Weather Service Norman OK
1023 AM CDT Wed May 23 2018

Isolated to scattered showers/storms possible this afternoon and
early evening. Highest chances will be over eastern portions of
the fa where better moisture is. Activity is expected to decrease
toward and after sunset due to the loss of heating.


.PREV DISCUSSION... /issued 440 AM CDT Wed May 23 2018/

12Z TAF discussion.

VFR conditions continue.

Mainly scattered high clouds today with some daytime cumulus. Some
convective activity possible during the mid/late afternoon into
early evening, but chances right now remain too low to mention in
the TAFs. Otherwise, a south/southeast wind mainly under 12kts
will continue through forecast.

PREV DISCUSSION... /issued 315 AM CDT Wed May 23 2018/

Hot temperatures and isolated mainly diurnally driven convection are
expected over the next few days. Opportunities for more organized
convection appear limited. The threat of severe thunderstorms is
present, but should remain isolated and brief for the most part.

Isolated to scattered diurnally driven convection is expected to
develop by mid-afternoon. Greatest coverage will be across eastern
portions of the area where weak mid-level perturbation and
deepest moisture (PWAT ~1.60 inches) will reside.

Sometimes in these tranquil synoptic summer-like patterns with a
very moist environment, very subtle small scale perturbations
aloft can enhance ascent just enough to generate mid-level
convection when surface-based instability is at a minimum.
Although we expect the activity over the next several days will
have the greatest coverage coincident with the diurnal maxima in
surface based instability, some isolated nocturnal activity may
become possible. There is some QPF signal across roughly the
eastern third of Oklahoma Thursday morning that is likely tied to
very weak ascent and low condensation pressure deficit values on
the 305k isentropic surface. We will keep and isolated <15 PoP for
southeast section of our area early Thursday to account for this

Some convection that forms and loosely organizes with cold pool
formation in the High Plains could move into western Oklahoma
Thursday evening. This could be enhanced by subtle vorticity at
the tail end of closed mid-upper low lifting out and through the
northern Rockies. This activity should dissipate quickly as
surface based instability diminishes.

Thermodynamic profiles by Friday that support large MLCAPE as
mid-upper flow veers with aforementioned passing wave, and dry
adiabatic layer is advected atop a moist boundary layer. Large
instability and significant theta-e differences in the vertical
(~30-35 K) will support downburst potential with any convection
that can form. Although subtle in model guidance, remnant low-
level boundary may reach the Kansas border or perhaps slightly
south. This may be enough for isolated to scattered convection
Friday afternoon through early evening. Weak flow aloft and
limited tilt to updrafts should result in short duration of
individual convective cells, but upon collapse, a brief bout of
hail and severe microburst potential seems relatively high.

On Sunday, mean ridging and height rises should preclude
convection across most of the area, but would have less influence
across our southeast counties, thus isolated thunderstorms are
possible there. Isolated severe storms with downburst potential
will again exist late Saturday with any storms that can form.

GFS and ECMWF ensemble mean have stabilized in the last few runs
with their depiction of the large scale pattern into early next
week. They, along with their deterministic counterparts, have
another closed mid-upper low over the Great Basin region which
deamplifies and slowly moves northeast early next week. This will
be a favorable large scale pattern to force deepening lee trough
and a westward upslope flux of low-level moisture leading to
increase in convection in the High Plains. This convection may
then drift east into western sections of our area each evening
Sunday through Tuesday. Thereafter, the system is expected to move
into Canada shifting the regime to hot/dry for us as ridging
builds across the Plains.



Oklahoma City OK  86  66  88  67 /  20  20  20  20
Hobart OK         88  66  89  67 /  20  10  20  20
Wichita Falls TX  88  67  90  68 /  10  10  10  10
Gage OK           89  64  91  66 /  20  20  20  20
Ponca City OK     87  66  88  67 /  20  20  30  30
Durant OK         88  67  89  67 /  40  30  30  30




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