Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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000
FXUS64 KOUN 241801
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
101 PM CDT Wed Apr 24 2019

.UPDATE...
A few adjustments were made to the previous forecast. In northwest
Oklahoma, temperatures were lowered due to persistent mid level
clouds which will prevent some daytime heating. Precipitation
chances were lowered in parts of western north Texas, as the
potential for showers and isolated thunderstorms have shifted
further east.

Zwink

&&


.AVIATION...
18Z TAFs

VFR conditions are expected to dominate as lower ceilings move out
of central Oklahoma and western north Texas. By 21Z, all sites are
anticipated to have VFR ceilings and visibilities. Surface winds
are expected to remain light and at times variable. A cold front
will begin moving into the region Thursday morning which will
bring a wind shift to the north and strong, gusty winds.

Zwink

&&

.PREV DISCUSSION... /issued 634 AM CDT Wed Apr 24 2019/

AVIATION...
24/12Z TAFs. IFR and MVFR conditions expected through 16-18Z most
terminals, with mainly VFR thereafter. Most of the rain today
expected to stay south/east of terminals. Some fog will be
possible late in the forecast period, but with some uncertainty
with respect to the amount of mid-high clouds, will not include in
this issuance. Winds will remain light.

PREV DISCUSSION... /issued 353 AM CDT Wed Apr 24 2019/

DISCUSSION...
An elongated northwest-southwest oriented vorticity maxima and
associated surface front has focusing some convection this
morning generally southeast of a Chandler to Norman to Lawton
line. These features will weaken/become diffuse later today, but
diurnal destabilization may support some renewed convection
near/southeast of this line through the afternoon. Coverage will
probably be minimal. Meanwhile, a closed low now over the Sonora
region of Mexico is shown in the models to move east-northeast and
pass through north Texas on Thursday. Increased ascent in
response to this system will probably result in another fairly
expansive area of rain mainly across north Texas but probably
extending into southern Oklahoma late in the day through the
evening. Rain associated with TROWAL/deformation development as
closed low deepens in northwest Texas tonight into early Thursday
morning will affect mainly our southeast counties. Rain is
expected to exit the region Thursday afternoon.

Expected amounts and duration as well as current flash flood
guidance all suggest there shouldn`t be significant concern for
flooding through Thursday. However, earlier heavier rains have
resulted in some main stems reaching flood, or expected to reach
flood. These include the Washita River near Carnegie and Anadarko,
and the North Fork Red River near Headrick.

Along the western and northern edge of thicker mid-high clouds,
radiative cooling, moist ground, high surface RH, and light winds
may contribute to some patchy fog late tonight and Thursday morning.
This would mainly be across portions of central and northern
Oklahoma.

The main challenge in the long term period is determining
placement of surface front across the area. A latitudinal sloshing
in response to central/northern Plains transient shortwave
activity, and possibly augmented by convection, makes placement of
precipitation probabilities a challenge. Medium range guidance
has trended toward a more active pattern with at last subtle
forcing for ascent from aforementioned perturbations aloft coupled
with a moist/unstable environment, periodic convection should
occur. Although the details of the pattern are uncertain at this
time range, the CAPE/shear parameter space suggests severe
thunderstorms could be a threat.

A vague first attempt at timing/coverage follows:

1) Upscale growth of central High Planes convection could track
east mainly across Kansas Friday eveing/overnight, but could
impact northern Oklahoma.

2) A low-probability of convection late Saturday roughly across the
southeast half of the area, near remnant surface front, though mid-
level height rises cast some doubt.

3) We broad brushed low probabilities Sunday night through Monday
night to account for model differences (faster ECMWF / slower GFS).
Greater convective coverage is likely to be in Kansas.

4) A more pronounced, albeit deamplifying wave attempts to phase
with northern stream as it ejects from the southwest. This may
provide subtle forcing atop substantial conditional instability and
result in a potentially organized/severe event Tuesday afternoon
and/or Tuesday night (faster GFS / slower ECMWF).

The disclaimer to the above is that although the general
timing/amplitude of waves in the models is fair considering the time
range up until mid-week, model run to run consistency has been
poor. So expect forecast refinements over the next few days as we
approach this potentially convectively-active pattern. Latest runs
have a general signal for troughiness across the west impinging
on our area for the latter half of the week supporting a
continuation of periodic convection, but confidence is below
average at this time given model differences and dramatic run-to-
run inconsistency.

BRB

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  67  52  76  51 /  20  20   0   0
Hobart OK         66  51  75  49 /  10  10   0   0
Wichita Falls TX  67  54  78  51 /  50  40  10   0
Gage OK           71  48  78  48 /   0   0   0  10
Ponca City OK     65  50  78  48 /   0   0  10   0
Durant OK         68  61  75  54 /  70  80  40   0

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&

$$

50/10/50


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