Area Forecast Discussion
Issued by NWS Oklahoma City, OK
FXUS64 KOUN 230938
Area Forecast Discussion
National Weather Service Norman OK
338 AM CST Mon Jan 23 2017
No significant changes were made to the previous forecast. Dry
weather will persist for at least the next seven days. Weather
impacts for the next several days should be limited to breezy/windy
conditions Tuesday and potential elevated to critical fire
weather conditions (see Fire Weather section below).
Latest upper air analysis shows ridging across the central and
southern Plains and a closed low off the Pacific Northwest coast.
Models are in decent agreement with broad western CONUS troughing
and also the evolution of another closed upper low over the central
Rockies progressing east into the central Plains on Tuesday. Looking
at current and previous runs of the GFS and ECMWF ensemble mean,
there is little discernible trend--perhaps a slight slowing in
more recent runs. GEFS is a little deeper than ECMWF ensemble
mean, but overall the position/track is similar. Small differences
in depth of the closed low, amplitude of upstream ridge, and
slightly different tracks in deterministic guidance have resulted
in some uncertainty with the placement of the mid-level wind
maxima on Tuesday afternoon. This is important for the wind and
fire weather aspects of the forecast. The ECMWF is slightly
further north and slightly slower with the core of mid-level winds
and would be most concerning for stronger wind gusts Tuesday
afternoon as we mix fairly deep. GFS shifts the speed max east
quicker and is at slightly lower in latitude with its position.
In either case, this is a favorable synoptic pattern for windy
conditions as a fairly intense surface low tracks to our north and
tight surface pressure gradient results across our area.
This system will send a cold front south into the area Tuesday
night bringing cooler temperatures (close to or slightly below
normal for late January) through the weekend.
Elevated fire weather conditions could develop across portions of
western Oklahoma this afternoon as southerly winds increase to
between 15 and 20 mph. However, minimum relative humidity values
are likely be no lower than about 25 percent near the border with
the Texas Panhandle. ERC values are still on the low end of
Elevated to critical fire weather conditions are expected to
develop Tuesday afternoon as much stronger southwesterly winds and
warmer conditions develop. Blended guidance is typically too high
with dew points in these situations where low level flow is
downslope and we warm and mix deeply. So, we have adjusted dew
points to be on the low end of guidance, closer to GFS raw, SREF
and ARW, and then made some manual modifications from there. We
also are on the high side of guidance for temperatures as there
also tends to be a low bias in the blends during these scenarios.
This yields afternoon minimum relative humidity values ranging
from the upper teens in the west to mid/upper 20s in the east. The
exception may be in the far southeast portion of the area where
low level moisture return may be more pronounced.
The combination of 20-foot winds and RH values will result in
meteorological conditions being met for critical fire weather
conditions across western Oklahoma and portions of western north
Texas with elevated fire weather conditions elsewhere except
perhaps the southeast where, as previously mentioned, low level
moisture may be more extensive. ERC values may still be on the low
end of average due to recent precipitation events but a trend
toward average values around 35 seem probable given dry windy
conditions this afternoon.
The best juxtaposition of low level thermal ridge and mid level
speed max may be across the southeast where low level moisture
return will be greatest, and RH values may not fall to critical
levels. Given this misalignment, and after collaboration with
offices to our west who have higher criteria for critical, and the
overall short duration and marginality of the event (especially
with respect to the state of fuels), we decided not to issue a
Fire Weather Watch. Although, confidence in far western portions
of the area at least briefly reaching low-end critical conditions
is reasonably high. We will continue to monitor trends.
Cooler more moist conditions after a frontal passage early
Wednesday should preclude fire weather concerns beyond Tuesday
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 61 42 70 33 / 0 0 0 0
Hobart OK 65 41 66 31 / 0 0 0 0
Wichita Falls TX 67 44 71 34 / 0 0 0 0
Gage OK 70 40 61 27 / 0 0 0 0
Ponca City OK 58 39 66 31 / 0 0 0 0
Durant OK 59 43 72 40 / 0 0 0 0