378
FXUS64 KTSA 211824
AFDTSA

Area Forecast Discussion
National Weather Service Tulsa OK
124 PM CDT Tue May 21 2024

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

.SHORT TERM...
(Through Tonight)
Issued at 119 PM CDT Tue May 21 2024

Warm, humid, and breezy conditions will continue through this
afternoon and evening. Storm chances will ramp up later this
afternoon and into the evening, continuing into the overnight hours
as a cold front moves into the area from the northwest. Model
guidance continues to show a deeply unstable atmosphere with
MLCAPE in excess of 3000 J/Kg through the afternoon and evening
south of the front. Surface-850 hPa specific humidity will be near
the 99th percentile for this time of year with IVT also near the
99th percentile as a consequence of an usually strong low pressure
to the northwest enhancing the southerly flow.

Initial convective initiation has already begun in south-central OK.
These elevated storms will move into southeast OK the next 2 hours.
The main severe hazard will be hail. Convective initiation along the
front is expected around 3-6 PM with a line of storms forming along
it. There will also be the potential for additional isolated
cells anywhere east or south of the front. These storms will be
capable of all severe hazards, including large hail, damaging
winds, tornadoes, and heavy rainfall leading to flash flooding.
CAMs remain a bit uncertain with respect to how far south along
the boundary storms will form. They also remain uncertain with the
coverage and intensity of storms ahead of the front. With this in
mind, the best coverage and intensity of storms will likely be
across far northeast OK and northwest AR during the early evening.

By late in the evening more widespread storm activity will develop
across southeast OK. Further north, storms will continue to develop
along the front, which will slowly sag south in the vicinity of I-
40. Some areas with repeated rounds of storms will see localized
flash flood potential. Due to recent rains, as well as the
expectation of continued heavy rain Wednesday, and low level
moisture remaining near the climatological max for this time of
year, a Flood Watch was issued through Friday morning to account
for this threat. CAM guidance shows a resurgence of elevated
storms along and behind the front in the 9-12Z period across the
area, but southeast OK in particular. These storms will once again
have the potential to become severe. Discrete cells and cells
north of the front would be hail dominant, but any storms near the
boundary would be capable of all severe hazards.

&&

.LONG TERM...
(Wednesday through Tuesday)
Issued at 119 PM CDT Tue May 21 2024

The cluster of storms mentioned at the end of the short term period
will progress east to northeast into northwest AR bringing
widespread heavy rainfall with some severe potential continuing. As
storms (presumably) grow upscale into a line, the threat of strong
winds would become dominant, but other severe hazards would remain
possible. CAM guidance is all over the place for later in the day
Wednesday, but the general theme is that multiple rounds of
additional showers and thunderstorms are likely, but will continue
to focus in southeast OK and northwest AR. As the cold front will be
near or south of the Red River by Wednesday, high temperatures will
be much lower. Highs in the mid 70s will be common north of the
boundary, except perhaps low 80s near the Red River. Low
temperatures north of the boundary will be in the low to mid 60s
and low 70s near and south of it.

For Thursday the remnant cold front will lift north, but it will
become diffuse and wash out. With warm and humid air streaming back
through the area and yet another shortwave trough moving through,
widespread storms are expected to develop again. Similar to the
preceding days, anomalous instability, moisture, and wind shear will
be present so severe weather is expected. Areas of heavy rainfall
will also occur.

Ensemble guidance is in decent agreement that we will get a break
from the storms Friday, with just some lower potential across the
terrain in Arkansas. Saturday will see storm chances resume, with
some lingering probabilities into Sunday. By early next week
ensemble guidance is in excellent agreement that a large ridge will
build across the Great Basin, bringing much warmer air back into the
area under northwest flow. However, smaller scale details such as
how strong the ridge will be or where it will center are still
unknown. About 40% of guidance position the ridge in a way that
would be favorable for nocturnal MCS activity, but given the lead
time will just go with NBM PoPs for now.

&&

.AVIATION...
(18Z TAFS)
Issued at 1227 PM CDT Tue May 21 2024

Corridor of low VFR to periodic MVFR ceilings will remain across E
OK / NW AR terminals this afternoon with isolated to scattered
showers and storms. Thunderstorm chances increase from late
afternoon through the evening as a cold front moves slowly
southward into the region. Periodic flight impacts are likely for
NW AR terminals with slightly lesser chances further west.
Lower ceilings develop again overnight along with a chance for
thunderstorm redevelop in vicinity of the slow moving cold front.

&&

.PRELIMINARY POINT TEMPS/POPS...
TUL   62  76  63  82 /  30  40  40  50
FSM   69  80  66  84 /  60  70  70  60
MLC   67  77  65  82 /  30  80  70  60
BVO   59  76  58  81 /  20  40  30  50
FYV   65  77  61  80 /  60  80  70  60
BYV   63  74  61  80 /  60  70  60  50
MKO   65  75  64  80 /  50  70  60  60
MIO   57  74  61  80 /  40  50  40  50
F10   63  75  63  80 /  50  70  60  60
HHW   70  80  66  82 /  30  80  70  60

&&

.TSA WATCHES/WARNINGS/ADVISORIES...
OK...Flood Watch from 7 PM CDT this evening through Thursday evening
     for OKZ049-053-072>076.

AR...Flood Watch from 7 PM CDT this evening through Thursday evening
     for ARZ019-020-029.

&&

$$

SHORT TERM...06
LONG TERM....06
AVIATION...07