976
FXUS64 KOUN 231847
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
147 PM CDT Thu May 23 2024

...New SHORT TERM, LONG TERM...

.UPDATE...
Issued at 1209 PM CDT Thu May 23 2024

Watching a complex severe weather forecast this afternoon and
evening. Boundary layer moisture return has been extremely robust
this morning following the overnight round of convection. The
outflow boundary from those previous storms could be seen in surface
observations as a sharp warm front across central Oklahoma; surface
wind fields on the Oklahoma Mesonet have shown a distinct diffusion
of this front over the last 2 hours. With that said, dewpoints in
northwest Oklahoma are in the mid-60s with a distinct gradient to
dewpoints in the low-to-mid 70s across western north Texas and
southern Oklahoma.

A stratus deck is also shown on satellite across most of the area,
particularly near the 100th meridian. Given the moisture advection
ongoing, there are some questions about how long this takes to mix
out. If stratus does linger into the afternoon, the severe risk
would likely be reduced. Over the past hour, however, GOES satellite
has shown some thinning of the stratus across the 100th meridian and
corresponding eastern portions of the Texas panhandle, which
coincides with an easterly push of the dryline off of the Caprock.
The expectation is that the western fringe of the cloud cover will
continue to downscale into cumulus over the next several hours,
which will allow for partial insolation.

The number of storms we receive is similarly in question and in part
dependent on how much insolation we receive. Most members of the
HREF/MPAS do try to cue up at least one or a few storms by late this
afternoon in western Oklahoma, with a particular focus on the triple
point between the effective warm front and the dryline. Meanwhile,
another area will be watched in southern and central Oklahoma where
some models have shown a signal for convection initiation within a
warm advection regime. There appears to be a negative correlation
between storm coverage in the two regimes; in other words, more WAA
storms to the east could reduce or even remove storm coverage along
the dryline later.

The early storms, should they develop, will have access to 3,000-
4,000 J/kg of MLCAPE and sufficient bulk shear for the development
of supercells. Low-level shear will be weak, so the main concern
would be for severe hail and damaging winds, but a very low tornado
risk would accompany these storms. Off to the west, any storms that
develop along the dryline will initially be favored to become
supercellular and produce large to very large hail. There is a
noticeable uptick in the LLJ on model guidance beginning about 8:00
pm, so there will be a window for any established supercells to
produce tornadoes this evening as they move eastward.

Meister

&&

.SHORT TERM...
(This evening through Friday)
Issued at 144 PM CDT Thu May 23 2024

Any severe weather that is ongoing from the near-term will linger
into the evening and overnight period. The threat for supercells
with tornadoes, very large hail, and damaging wind gusts will
persist with aid from a strengthening LLJ in the 7:00 pm to 10:00 pm
timeframe. At some point during the early overnight period,
stabilization of the surface layer should bring an end to this round
of storms.

Mercifully, CAM guidance doesn`t show any indication of an
overnight/early morning round of storms tomorrow morning. The night
will be very humid with lows only dropping into the upper 60s to
near 70 across much of the area. The exception will be in northern
Oklahoma, where a cold front will come sweeping in just before
daybreak. Marginally cooler and drier air will filter in behind this
cold front.

That cold front will continue to push south through late morning, by
which point it will be roughly along the I-44 corridor. Here, most
guidance indicates a significant slowing of the frontal boundary as
it encounters the rougher terrain south of I-44. With MLCAPE in
excess of 4,000 J/kg on the warm side of the front and considerable
convergence, convection initiation is likely by midafternoon
southeast of a line from Seminole to Ardmore. Shear profiles should
favor initial supercellular mode with large to potentially very
large hail and a very low tornado risk. The undercutting nature of
the front will likely limit the discrete supercellular window, with
storms either becoming elevated or potentially growing upscale into
clusters. The risk would then transition to hail and damaging winds.
These storms should exit our area by mid-evening.

For those of you who are behind the front, make sure to get outside
and enjoy the afternoon. Highs will remain in the low 80s with
humidity decreasing throughout the day. This may be one of your last
chances to enjoy dewpoints under 45 with temperatures under 100
before September, so enjoy it!

Meister

&&

.LONG TERM...
(Friday night through next Wednesday)
Issued at 144 PM CDT Thu May 23 2024

Next verse, same as the first: Saturday`s storms might be a little
bit louder and they might be a whole lot worse.

A 60-knot west-southwesterly mid-level jet ejecting directly into
our area isn`t terribly common in May, but that`s what pretty much
every model is showing. Equally concerning is the degree with which
models show this jet streak overspreading a tight dryline with 3,000-
5,000 J/kg of MLCAPE in the afternoon. And to add another layer to
the concern, the GFS/FV3/NAM all show that region immediately to the
east of the dryline to be characterized by classic sickle-shaped
hodographs with 0-3 km SRH approaching 300 J/kg. This environment
would be very favorable for the development of multiple supercells
in the afternoon across western Oklahoma and western north Texas.
Those supercells would be capable of tornadoes (some of which may be
strong), large to giant hail, and damaging wind gusts.

Uncertainty continues to lower as we pull within 60 hours of
Saturday evening, and with it the higher-end outcomes appear to be
increasing in probability with no "failure modes" immediately
obvious that may mitigate the risk. This spring has taught and
retaught the lesson that we still have so much left to learn when it
comes to severe weather; there is still plenty of opportunity for
some sort of synoptic, mesoscale, or storm-scale detail to show up
that may prevent us from experiencing a high-end severe weather
event. With that said, at a minimum we urge people to continue to
follow updates with the forecast as Saturday approaches.

The dryline will mix further to the east on Saturday. This will
focus the severe risk in or east of our eastern counties. For the
rest of us, downsloping winds will lead to a hot afternoon across
much of the area.

Another cold front should intrude through much of the area Sunday
night through Monday afternoon. Monday does look like the best bet
to be our first no-storms day in a while, with cooler temperatures
and drier air look to be filtering in. The early part of next week
looks to be a game of sloshing moisture with northwest flow aloft.
Right now, the best guess is that highs will be warm but not hot,
and precipitation chances will exist but can`t be pinpointed yet.

Meister

&&

.AVIATION...
(18Z TAFS)
Issued at 1237 PM CDT Thu May 23 2024

Current stratus deck will slowly scatter with increasing
visibilities as all terminals should return to VFR conditions
around 20-21Z. Isolated thunderstorms will be possible and could
impact some of our terminals between 22-04Z with probabilities up
to 50 percent. Although storm activity could reduce conditions
below VFR conditions, expecting another stratus deck to lower
ceilings to MVFR to IFR between 05Z-10Z with low confidence of
reduced visibility`s in fog down to 2 miles at some terminals. A
cold front will be pushing into northern Oklahoma after 12Z as
surface winds will be shifting out of the north behind the front.

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  82  68  84  61 /  50  30  10   0
Hobart OK         89  66  84  59 /  30  20  10   0
Wichita Falls TX  89  69  89  64 /  30  20   0   0
Gage OK           91  58  81  53 /  20  20   0   0
Ponca City OK     83  67  81  56 /  40  30  20   0
Durant OK         84  69  90  68 /  50  40  20  10

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Flood Watch until 1 AM CDT Friday for OKZ032-041>043-046>048-
     050>052.

TX...None.
&&

$$

SHORT TERM...04
LONG TERM....04
AVIATION...68