844
FXUS64 KTSA 201718
AFDTSA

Area Forecast Discussion
National Weather Service Tulsa OK
1218 PM CDT Fri Sep 20 2024

...New AVIATION...

.SHORT TERM...
(The rest of today)
Issued at 1020 AM CDT Fri Sep 20 2024

Showers and thunderstorms have developed across the northwestern
fringes of the forecast area this morning, with GLM and NLDN data
indicating the bulk of the lightning threat isolated to portions
of Osage County so far. An earlier update added slight chance POPs
for this activity, isolated to portions of northeast Oklahoma west
of Highway 75. This mention has been extended through 18Z, with
the mention of thunderstorms limited to areas near the Kansas
border given recent radar and lightning observations. The
expectation remains that this activity should diminish toward
midday. Additional isolated to possibly, scattered showers and
thunderstorms remain expected across the northern fringes of the
area, including into far northwest Arkansas, with the bulk of the
afternoon/evening development still expected to be just outside
the forecast area.

On the heat and humidity front, minor adjustments were made to
both temperatures today and to the dew point trends, using
influence from the HRRR for temperatures and the HREF for dew
points. This did not change the expectations of afternoon heat
index values right around/just above 105 for a good chunk of
eastern Oklahoma and in the Arkansas River Valley areas. The Heat
Advisory appears good area/impact wise for now, with the only
concern being areas where the mid cloud and precipitation may keep
the higher temperatures from being realized.

The only other notable adjustment to the previous forecast has
been to the Sky cover, as the NBM continues to underforecast cloud
cover even in the near term. Have adjusted the Sky cover upward with
the NBM 90th percentile to more closely match current satellite
observations/trends.

Updated forecast already out.

&&

.LONG TERM...
(Tonight through Thursday)
Issued at 210 AM CDT Fri Sep 20 2024

Over the next several days the strong ridge of high pressure that
has been centered over and south of the area will begin to weaken
and shift south in response to an approaching upper level trough
from the west. In spite of upper level cooling, the lower levels
will remain quite hot, with high temperatures once again in the mid
90s to near 100 F. As the previously mentioned trough approaches, a
few late afternoon or evening storms may develop Saturday, with
the best chance in northwest AR.

Some cooling will likely begin Sunday with more extensive cloud
cover. Additionally, an upper level jet streak will increase mid
level flow, wind shear, and upper level divergence. These
factors, along with sufficient instability, will likely result in
a round of showers and thunderstorms along a frontal boundary.
There is a marginal risk (5% chance) that a few of the storms
could be severe. This will be the best and most widespread chance
of precipitation for most areas during the forecast period, with
Pops of 40-60% most areas. A few areas of locally heavy rainfall
could result in minor flash flooding, but recent dry conditions
will mostly limit that threat.

Model guidance remains in good agreement for Monday, with much
cooler temperatures moving into the area. Most areas will remain in
the 70s with relatively dry conditions developing from northwest
to southeast during the day. The forecast becomes much more
uncertain for the middle to end of next week. Ensemble guidance
does agree that behind the previously mentioned trough, a
secondary upper level trough will dive south. However, model
guidance is very inconsistent with this feature. Some guidance
merges the two upper lows and they stay over the area with very
cool and showery conditions, while other guidance moves the new
upper low to the east leaving us cool but mostly dry. Still other
guidance takes the initial low east while the follow on low goes
west and a ridge builds over the area. Suffice it to say, the
spread of possible outcomes is very high for next week. Guidance
is roughly evenly split between these generalized outcomes, so no
particular solution is favored at this time.

&&

.AVIATION...
(18Z TAFS)
Issued at 1218 PM CDT Fri Sep 20 2024

VFR conditions are forecast to persist through the period.
Thunderstorm redevelopment remains expected later this afternoon
and into the evening that could impact mainly the NE OK and far NW
AR terminals, but coverage is expected to be small enough to leave
any impacts out of the TAFs at this point. Gusty winds ongoing at
the NW AR sites should diminish by early evening.

&&

.PRELIMINARY POINT TEMPS/POPS...
TUL   77  98  75  90 /  20  20  20  40
FSM   76  97  75  93 /  10  20  10  10
MLC   74  98  73  94 /   0   0  10  10
BVO   73  99  70  88 /  20  20  30  60
FYV   73  92  70  89 /  20  30  20  30
BYV   73  92  71  90 /  20  40  20  30
MKO   76  96  74  92 /  10  20  10  20
MIO   74  96  71  89 /  20  20  30  50
F10   74  98  73  92 /  10  20  10  30
HHW   73  96  72  93 /   0   0   0   0

&&

.TSA WATCHES/WARNINGS/ADVISORIES...
OK...Heat Advisory until 8 PM CDT this evening for OKZ054>057-059>062-
     064>068-070>076.

AR...Heat Advisory until 8 PM CDT this evening for ARZ019-020-029.

&&

$$

SHORT TERM...22
LONG TERM....06
AVIATION...22