Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 152332 AAA

Area Forecast Discussion...UPDATED
National Weather Service Norman OK
632 PM CDT Thu Mar 15 2018

16/00Z TAFs. VFR conditions are expected to prevail with potential
for MVFR stratus expected to stay just south and east of KSPS and
KOKC/KOUN terminals in the 09-13Z timeframe. Will monitor this for
possible inclusion in next issuance. Winds will remain strong and
veer to southwest and eventually west first half of the forecast


.PREV DISCUSSION... /issued 408 PM CDT Thu Mar 15 2018/

Fire weather and the chance for thunderstorms/severe weather on
Sunday are the primary forecast issues for this period.

For tomorrow, a dryline is expected to quickly shift eastward as
winds veer to the west during the morning hours as a surface
cyclone moves eastward across the I-70 corridor in Kansas.
Forecast soundings indicate rather deep mixing behind the
dryline--potentially to near 700 mb--which will allow for breezy
westerly winds. Opted to increase winds above blended guidance and
warm temperatures toward GFSX MOS guidance to account for the
deep mixing.

As the attendant surface cyclone passes eastward, a cold front
will pass by late Friday into Saturday. Slightly cooler weather is
expected for Saturday, but temperatures are forecast to be above
average in the mid-60Fs to low 70Fs.

For Sunday, the potential for severe thunderstorms will be
modulated by moisture return and any convective contamination.
The 15/12Z NAM is quite aggressive with moisture return, and the
15/12Z ECMWF is also more aggressive than the previous run. As a
negatively-tiled shortwave trough approaches, NAM forecast
soundings indicate that ascent/height falls may sufficiently erode
the cap to allow for isolated thunderstorms to develop along the

Well ahead of the dry line, showers/storms are forecast to
develop ahead of the shortwave trough--especially across southern
Oklahoma and perhaps even central Oklahoma--due to isentropic
ascent/warm air advection. One potential caveat that could
mitigate the potential for severe weather is if convection
associated with isentropic ascent develops early enough in the
day where it could limit instability/insolation.

Nevertheless, if surface-based thunderstorms are able to develop,
the parameter space would be favorable for severe thunderstorms
with effective bulk shear >40 knots and perhaps ~1000 J/kg of
MLCAPE (if the the NAM and ECMWF dew points are realized and there
is limited convective contamination).

As this system exits late Sunday into Monday, wrap-around clouds
precipitation may impact the northern half of Oklahoma. Cooler,
seasonable temperatures are expected in the front`s wake for
Monday and Tuesday. High temperatures may only be in the upper
50Fs to mid 60Fs on Tuesday afternoon.

Relatively tranquil weather is expected through Thursday with a
warming trend as southerly winds return across the area.


For Friday, the ongoing Fire Weather Watch has been upgraded to a
Red Flag Warning.

As a closed, vertically-stacked low moves across the Kansas/Nebraska
border, the attendant dryline will quickly shift eastward Friday
morning and should be east of I-35 by late morning with surface
winds veering to the southwest and then to the west. The low-
level/850 mb thermal ridge is forecast to be oriented along a line
from southwest Oklahoma/western north Texas, northeastward into
north central Oklahoma.

Relative humidity values will fall below 20% across much of the area
with some locations in southwest Oklahoma and adjacent parts of
north Texas having forecast relative humidity values below 10%.
Forecast soundings indicate rather deep mixing behind the dryline--
potentially to near 700 mb--which will allow for breezy winds (20 to
30 mph with higher gusts above 40 mph) as well.

The combination of warm temperatures, low relative humidity values,
and wind speeds will result in critical fire weather conditions
across much of the area.

In addition, ERC values are above the 90th percentile northwest of I-
44, so fuels in this area are quite volatile due to the ongoing
drought conditions and lack of precipitation. There is a gradient
in ERC values near I-44, with much lower values across far
southeast Oklahoma (where precipitation has been more recent).
Therefore, the Red Flag warning does not include these areas.
Relative humidity should be a little higher in this area as well.

For Sunday, fire weather conditions may become at least near-
critical far western north Texas and perhaps western Oklahoma as
another dryline moves eastward. The uncertainty is how far east
the dryline will mix. Currently, it appears it could be fairly
close to the 100th meridian.

Post-frontal, gusty northwesterly winds may result in continued
elevated to near-critical fire conditions on Monday as well.



Oklahoma City OK  54  79  43  68 /  10   0   0   0
Hobart OK         50  80  41  69 /  10   0   0   0
Wichita Falls TX  55  82  44  71 /  10   0   0   0
Gage OK           51  75  36  68 /   0   0   0   0
Ponca City OK     56  79  38  67 /  10   0   0   0
Durant OK         61  81  49  73 /  10  10   0   0


OK...Red Flag Warning from 11 AM to 8 PM CDT Friday for OKZ004>042-

     Red Flag Warning until 8 PM CDT this evening for OKZ004>006-

TX...Red Flag Warning from 11 AM to 8 PM CDT Friday for TXZ083>090.

     Red Flag Warning until 8 PM CDT this evening for TXZ083-084-087.



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