Area Forecast Discussion
Issued by NWS Oklahoma City, OK
FXUS64 KOUN 240248
Area Forecast Discussion
National Weather Service Norman OK
948 PM CDT Thu Mar 23 2017
Decreased precipitation chances overnight.
A line of thunderstorms continues to push eastward across western
Kansas and the Panhandles this evening. Surface analysis reveals
the surface front has about caught the dryline. Ahead of the
combo, south winds remain strong, gusting over 30 kts, approaching
40, across most of western and central Oklahoma. Surface dew
points are rather unimpressive ahead of the line of storms, and
surface based instability will continue to trend downward. Expect
thunderstorms to weaken as they push eastward into western
Oklahoma, with scattered showers and thunderstorms holding on
through the overnight, as the front pushes east. In response,
backed off on precipitation chances quite a bit overnight, with
the best chances for isolated to scattered development across
southern Oklahoma and northern Texas.
.PREV DISCUSSION... /issued 710 PM CDT Thu Mar 23 2017/
Strong south winds will continue tonight and become southwest
tomorrow. A front will shift wind to northwest in the afternoon in
northwest Oklahoma. VFR conditions are expected outside of a small
chance for showers/thunderstorms in northwest Oklahoma before
PREV DISCUSSION... /issued 322 PM CDT Thu Mar 23 2017/
An active weather pattern will continue into next week with
several weather hazards possible. Short term concerns are ongoing
windy conditions and fire weather concerns today, followed by
thunderstorms tonight. Windy and dry conditions will again lead to
fire weather concerns tomorrow afternoon and thunderstorms could
redevelop across eastern portions of the area by late morning.
Other active periods include Sunday (potential for severe
thunderstorms) and the middle of next week when rain and
thunderstorm chances increase again.
Latest water vapor channel imagery shows a deepening trough over
Utah moving east toward our area. In response, significant lee
side surface pressure falls are occurring today causing strong
winds across our area. Latest Oklahoma mesonet observations show
several locations in western Oklahoma have gusted to around 40 mph
or slightly higher.
Cooling/ascent from approaching trough/closed low atop a moist
boundary layer should yield at least weak instability across the
Panhandles this afternoon. Deep mixing/drying of the shallow low
level moist layer should temper significant destabilization.
Nevertheless, thunderstorms will likely develop and move east
reaching western Oklahoma later in the evening in a weakly unstable
(albeit decreasing) environment. A decrease in intensity and
coverage is expected as the storms move into northwest Oklahoma by
mid-late evening with the severe threat quickly decreasing. A
continued decrease in coverage will occur throughout the night.
This system is expected to evolve into an intense closed low
overnight with 20+ dm 6 hour 500 hPa height falls across southwest
Kansas before the system begins to fill slowly during the day. There
is some uncertainty on the exact track of the surface low. GFS and
its ensembles as well as the ECMWF track the low east-southeastward
across northern Oklahoma during the day, while NAM and SREF keep it
slightly further north. This has some implications for the wind
forecast. Current indications are that sustained winds of 25 to 35
mph will be common from late morning into the afternoon, with even
higher sustained speeds possible briefly over portions of western
north Texas. Deep mixing and momentum transfer seen in forecast
soundings could result in wind gusts to around 50 or slightly
higher, especially in the southwest portion of the area. A Wind
Advisory will likely be needed for this area and areas further
northeast including OKC tomorrow as gusts to around or just above
40 mph seem probable.
The next shortwave trough will approach Sunday. Low level moisture
will return but probably not until late in the day contributing
to only weak instability through the afternoon. Nevertheless deep
layer shear will be supportive of strong to severe thunderstorms.
Given the trends in low level moisture return, we have lowered
precipitation probabilities during the day. Convection may become
more numerous during the night warm/moist advection continues and
forcing from the passing wave occurs.
GFS and its ensembles remain somewhat slower with the next closed
low compared to the ECMWF. This would affect our area by mid-week
and have made little changes to the precipitation probabilities
during this time frame.
Elevated to near critical fire weather conditions are ongoing
this afternoon with RH values ranging from around 30 to 45 percent
across the area precluding a more significant fire weather
concern. Nevertheless, southerly winds of at least 20 mph across
much of the area and as high as 30 mph in western Oklahoma have
been observed. Gusts approaching or exceeding 45 mph have also
been seen over western Oklahoma. RH values should recover to
around or above 70 percent later tonight across all but western
north Texas, where RH values may not rise about 60 to 65 percent.
Tomorrow brings greater concern for fire weather. Critical
conditions seem quite possible, and a Fire Weather Watch is in
effect. The watch has been expanded to encompass a greater portion
of central Oklahoma. A low level thermal ridge will be oriented
from near or just east of Stillwater south-southwestward into
south- central Oklahoma, and the most fire effective conditions
may be just on the windward side of thermal ridge. This is not the
classic setup with a strong mid-level speed max crossing the
thermal ridge so this leaves some this should temper winds speeds and
limiting the fire potential somewhat. However, wind speeds will be
high enough to meet critical thresholds and deep mixing behind a
progressive dryline will support RH values as low as around 15
Visually, fuels are increasing in greenness but ERC-G values
remain on the high end of average and are still supportive of fire
growth and spread.
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 60 79 48 68 / 20 10 10 0
Hobart OK 55 77 44 71 / 30 0 0 0
Wichita Falls TX 59 83 47 73 / 30 10 0 0
Gage OK 51 69 39 69 / 50 20 10 0
Ponca City OK 62 79 48 65 / 20 20 30 0
Durant OK 61 79 51 72 / 30 70 10 0
OK...Fire Weather Watch from Friday morning through Friday afternoon
Wind Advisory until midnight CDT tonight for OKZ004>019-021>025-
Wind Advisory from 10 AM to 7 PM CDT Friday for OKZ021>023-027-
TX...Fire Weather Watch from Friday morning through Friday afternoon
Wind Advisory until midnight CDT tonight for TXZ083>090.
Wind Advisory from 10 AM to 7 PM CDT Friday for TXZ083>090.