Weather Forecast Discussion


000
FXUS64 KOUN 242338
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
638 PM CDT Sat Jul 24 2021

...New AVIATION...

.SHORT TERM...
(This evening through Sunday)
Issued at 227 PM CDT Sat Jul 24 2021

The always challenging weak summer nocturnal convection spawn from
very subtle mid-level forcing will be present to some extent for the
next few days. Also, building heat and humidity will cause some
concerns for heat stress in the coming days. Otherwise, weather
impacts should be minimal. Meteorological analysis and discussion
of forecast uncertainties can be found below.

Of highest priority, the latest observation show many areas at or
close to 105F heat advisory criteria early this afternoon and we
issued a Heat Advisory through 7pm. Even for areas that don`t
quite reach legacy criteria, winds are light enough to push wet
bulb globe temperatures into the "high" or "extreme" category.

Isolated convection may form later today with continued
destabilization of a moist PBL. This would be most likely on the
northwest extent of satellite-derived TPW axis in northwest Oklahoma
where there is a weak signal for very weak low-level convergence.
Without more defined convergence, convective coverage is expected
to be very limited justifying only low probabilities. Weak
tropospheric flow and still somewhat poor midlevel lapse rates
will preclude robust/severe convection.

Some altocumulus was observed today, along with a couple isolated
showers early this morning rooted in this moist mid-level layer.
Overall, coverage of rain was very limited since a warm subsident
layer has been persistent above the mid-level moist layer. Hysplit
backwards trajectories show subsiding parcels slowly moving
northeastward within weak flow on the eastern periphery of the
closed upper low which continues to retrograde and is now over
northwest New Mexico. Models do show some cooling of this warm
layer that when coupled with increase moistening mid levels should
support greater coverage of weak convection tonight, compared to
last night. Subtle forcing mechanisms are difficult to see within
the model guidance but seem to be focused mostly across northwest
Oklahoma, and this is where we have the highest precipitation
probabilities. Some adjustment may be needed later based on
observational trends.

Given the mechanism for overnight convection, it seems unlikely that
substantial cool pool will impact temperatures tomorrow
afternoon. Without strong reasoning to believe dew points will be
dissimilar tomorrow compared to today, we will likely be issuing a
Heat Advisory likely for the same areas tomorrow, once we finish
collaboration with surrounding offices. From a practical
standpoint with light winds, wet bulb globe temperatures will
likely again reach at least the high category.

Later Sunday, some form of a remnant weakly baroclinic front or
composite outflow should result in convergence of a moist
destabilizing atmosphere resulting in surface based convection.
This is most likely in southern Kansas, with more isolated
development further south into northwest Oklahoma where weak
convergence is indicated. Hi-res guidance suggest cold pool
development and some propagation into northwest Oklahoma by
evening, though mean cloud layer flow will be weak.

BRB

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 227 PM CDT Sat Jul 24 2021

There are mixed signals on specifically where convective coverage
may be greatest Sunday night either from remnant diurnal
convection and/or midlevel warm advection-driven development later
in the night. For that reason, we`re fairly broad with low
probabilities mainly over northern Oklahoma. But there is a
nonzero chance near the I-40 corridor.

For the rest of the long term period, broad ridging develops across
the western two-thirds of the country and will be initially centered
to our northwest early in the week before drifting slowly southeast
while expanding further late in the week. The most significant
positive height anomalies will remain to our north, and this
placement is not optimal for excessive heat in our region.
Nevertheless, 2-m temperatures about 5 degrees above climatology are
expected and enough moisture for heat indices near Heat Advisory
criteria, especially midweek onward.

BRB

&&

.AVIATION...
(00Z TAFS)
Issued at 635 PM CDT Sat Jul 24 2021

Will keep forecast VFR through this cycle, but will introduce
chances for TSRA. VCTS will be used for the first few hours of
forecast at KPNC with high based convection just west of terminal.
Thinking that current convection across far northern Oklahoma and
southern Kansas will decrease in coverage after 00Z. Outflow
induced surface trough (from tonights northern Kansas convection)
may have impacts on northern Oklahoma terminals tomorrow in the
form of a focusing mechanism for SHRA/TSRA. Will include PROB30
at northern Oklahoma terminals and will narrow to most likely time
to see any impacts, toward and after 21Z.

&&

.UPPER AIR...
Issued at 304 PM CDT Fri Jul 23 2021

No upper air flights are planned at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  75  97  74  97 /  10  10  10  20
Hobart OK         74  99  72  98 /  10  20  10  10
Wichita Falls TX  74 101  73 101 /   0  10  10  10
Gage OK           73  96  70  96 /  20  20  30  20
Ponca City OK     75  95  73  93 /  20  30  20  30
Durant OK         74  99  74  99 /   0   0   0  10

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Heat Advisory until 7 PM CDT this evening for OKZ007-008-012-013-
     018>020-024>032-039>043-045>048-050>052.

     Heat Advisory from noon to 7 PM CDT Sunday for OKZ007-008-012-
     013-018>020-024>032-039>043-045>048-050>052.

TX...None.
&&

$$

SHORT TERM...12
LONG TERM....12
AVIATION...11

NWS OUN Office Area Forecast Discussion