804
FXUS64 KOUN 011829
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
129 PM CDT Wed May 1 2024

...New SHORT TERM...

.SHORT TERM...
(This afternoon through Thursday night)
Issued at 129 PM CDT Wed May 1 2024

***This Afternoon into Tonight***

As a wise man once said: It`s gonna be May.

We`re ringing in the traditional most active month of the year with
a highly complex forecast for both severe and flooding potential
this evening. This morning`s convection has left a rather
substantial cold pool with theta-E perturbations on the order of
4-10 Kelvin across central Oklahoma. Recovery is uncertain within
our area, but West Texas Mesonet observations show a narrow plume
of upper-60s dewpoints gradually advancing northwestward across
the eastern Texas panhandle. Currently, the dryline is retreating
westward, but with increased diurnal heating it will likely
advance back into the eastern panhandle. The third boundary of
note in our forecast is what appears to be the synoptic-scale warm
front, which meets the dryline at a triple point low near
Perryton and extends east-northeast from there toward Medford.

Convection initiation appears probable in spite of the intrusion of
the cold pool into central Oklahoma. The two likeliest zones for CI
are:

-Along the outflow boundary in the southeastern TX panhandle
-Near the triple point in the northeastern TX panhandle

Outflow boundary region:

The presence of near-70 dewpoints and 3,000 J/Kg of MLCAPE will
encourage thunderstorm development likely by mid afternoon. The
initial mode will favor supercells capable of very large hail. Over
time, CAMs show a tendency to weaken the 500 mb winds while
increasing the LLJ. This will probably encourage supercells to grow
upscale into an eastward-propagating squall line. Given the depth of
boundary-layer winds and drying in the mid-levels to raise DCAPE to
1,400 J/kg, damaging wind gusts will become a threat toward sunset
with a potential in southwest Oklahoma and western north Texas for
significant (70+ mph) wind gusts. The tornado threat is conditional,
and may be most focused in the spatiotemporal window where the LLJ
is increasing directly along the remnant OFB. After sunset, this
cluster will continue eastward toward south central Oklahoma, likely
weakening over time. A second threat will occur overnight with this
cluster - flooding. One-hour flash flood guidance sits as low as 1.6-
2 inches of rain across much of southwest Oklahoma and as low as 1
inch in the Arbuckles. Even a small residence time of storms in this
area overnight could trigger recurrence of flooding.

Triple point region:

Storm coverage is more uncertain here as ongoing stratus/need for
further moisture advection cast doubt on reaching convective
temperatures. However, CAM guidance (notably the HRRR and MPAS) has
become much more bullish in the late morning hours on depicting the
development of scattered supercells by late afternoon. The longevity
of these storms will be dependent on sufficient theta-E advection to
overcome the development of a modest capping inversion after sunset.
However, shear profiles will be sufficient for supercellular
structures with the potential for large to very large hail. The
frontal boundary may also become a focus for tornado potential
toward sunset as the LLJ enlarges. CAM guidance is less bullish on
the potential for an overnight MCS across north central Oklahoma;
thus, it is anticipated that this activity will weaken after sunset.

Meister

***Thursday into Thursday Night****

By tomorrow (Thursday) afternoon, a slowly-advancing cold front will
be located somewhere in close proximity of I-44. The location of
this cold front will likely be affected by tonight`s convection
with some spread among guidance. In addition, a dryline will be
located in the eastern Texas panhandle or western north Texas.
Both of these surface boundaries will be likely focus for
convective during the afternoon and evening hours as convective
inhibition weakens with daytime heating.

Effective bulk shear will be weak to modest at only ~30 knots, so
transient supercell structures are possible. Even so, significant
hail is possible given the modest cloud layer shear (~50 knots),
weak low-level shear, and significant instability (MLCAPE >3000
J/kg). In addition, large downdraft CAPE (>1000 J/kg) may result
in damaging wind gusts. The tornado risk is generally low, but if
a supercell could constructively interact with the cold front or
an outflow boundary, the tornado potential would be higher
(especially given the magnitude of instability). Thunderstorms
may grow upscale into clusters and move to the southeast late
evening into the overnight hours. Flooding will become a hazard,
especially for locations that have had recent heavy rainfall.

Mahale

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 253 AM CDT Wed May 1 2024

By Thursday a cold front is expected to progress south and eastward
across the area. With an unstable airmass in place ahead of the
boundary, strong to severe storms will be possible once again. The
front will clear the area Thursday night but will quickly return
northward during the day on Friday, bringing renewed chances for at
least scattered thunderstorm development. Models are also now
showing a second cold front moving into northern and western
Oklahoma very late Friday night, with a complex of storms possible
here.

Storm chances then continue Saturday and Sunday as a moist and
unstable airmass remains in place and at least modest southwesterly
flow is maintained aloft. There is some signal for a potentially
more significant trough ejection into the plains on Monday, but
models disagree on timing and location of any attendant severe
risk at this range.

Ware

&&

.AVIATION...
(18Z TAFS)
Issued at 1201 PM CDT Wed May 1 2024

Southerly winds will continue through the remainder of the
period. Thunderstorms are expected to form along a dryline in
western Oklahoma late this afternoon and evening. These storms are
expected to move eastward, with a low probability of affecting
the rest of the TAF sites. Stratus will move in by tomorrow
morning, affecting each site.

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  81  64  78  59 /  40  40  80  40
Hobart OK         83  61  82  57 /  40  60  40  30
Wichita Falls TX  82  64  83  62 /  30  60  50  40
Gage OK           88  58  78  49 /  40  30  30  20
Ponca City OK     80  64  76  55 /  80  40  90  40
Durant OK         84  65  79  64 /  50  70  80  60

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Flood Watch through Thursday morning for OKZ035>041-044>046-050.

TX...Flood Watch through Thursday morning for TXZ084>090.

&&

$$

SHORT TERM...4/10
LONG TERM....08
AVIATION...13