Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 170351 AAB

Area Forecast Discussion...UPDATED
National Weather Service Norman OK
1051 PM CDT Fri Mar 16 2018

17/06Z TAFs. VFR conditions expected to prevail through this
TAF forecast period. Mainly light north and northeast winds will
prevail before winds veer to southeast late in the period across
western Oklahoma. Ahead of incoming storm system, mid-level cloud
cover will increase substantially after 12Z. -RA/-TSRA chances
will begin to increase toward the end of this forecast period and
beyond, primarily across areas from KSPS northeast to KOKC.


.PREV DISCUSSION... /issued 651 PM CDT Fri Mar 16 2018/

See aviation.

All terminals will remain under VFR conditions through the
forecast period, with only some mid to high level cloudiness
increasing. A cold front currently spread across northwest
Oklahoma will continue to push southward as the evening progresses,
resulting in surface winds shifting out of the north at around 10

PREV DISCUSSION... /issued 418 PM CDT Fri Mar 16 2018/

The primary forecast issue is the risk for severe weather on

Surface winds should decrease markedly this evening as vertical
mixing ceases and the pressure gradient relaxes. A wind shift will
pass by this evening, which will shift the winds to the north. Light
northerly winds and a dry airmass will result in an environment
favorable for radiational cooling. Low temperatures are expected
to range from the mid-30Fs to mid-40Fs across the area. Saturday
should be a seasonable day with high temperatures mid-60Fs to low
70Fs with light winds.

By Saturday night into Sunday, mid-level height falls and attendant
lee cyclogenesis will result in surface winds veering to the
southeast as the surface ridge moves eastward. Isentropic ascent and
moisture advection will result in low clouds Sunday morning--especially
across southern Oklahoma. Some showers/storms may develop across
southeast Oklahoma/near the Red River as well.

For Sunday morning, the 16/12Z GFS and NAM both indicate a lead jet
streak/lobe of vorticity may provide sufficient ascent for elevated
convection Sunday morning into the early afternoon--generally along
and east of I-35. This precipitation may move northeastward into
north central/eastern Oklahoma by early afternoon.

By late Sunday afternoon/evening, a shortwave trough and attendant
100-knot mid-level jet will approach the Southern Plains. The 16/12Z
NAM continues to suggest that ascent downstream of the shortwave
trough will be sufficient to erode the cap, and that there could
be convective initiation ahead of a dry line.

Progged effective bulk shear >40 knots and MLCAPE >1000 J/kg will be
sufficient for severe thunderstorms, including supercellular
structures. The greatest potential for severe weather may be across
south central into central Oklahoma, where the greatest instability
is forecast; however, severe weather will even be possible across
north central Oklahoma where there would be elevated instability in
association with the upper-level low. Large hail will be possible
due to steepening mid-level lapse rates with cold air aloft. Gusty
winds may also develop as strong forcing could promote the
development of line segments.

The severe weather potential will be modulated by three factors:

1) Convective contamination/insolation: If the convection
associated with the lead wave persists longer into the afternoon
hours, it would limit instability/insolation and temper the risk
for severe weather.

2) Moisture return: The NAM continues to be quite aggressive with
moisture return. It continues to suggest dew points could range
into the upper 50Fs in central Oklahoma to low 60Fs across south
central Oklahoma. Greater moisture return would enhance the severe
weather potential by increasing instability and lowering LCL

3) Timing of the mid-level wave: The most-pronounced ascent is
currently forecast during the mid to even late evening hours. This
may decrease the risk when compared to an afternoon timing of

In addition to severe weather, critical fire weather conditions
may develop across far southwest Oklahoma and adjacent parts of
north Texas Sunday afternoon (behind the dry line).

As this system exits late Sunday into Monday, very gusty
northwesterly winds are expected behind the system. The NAM has
850 mb winds >60 knots progged across northwest Oklahoma on
Monday morning, which may result in elevated to near critical fire
weather conditions.

Cooler 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.

A warming trend is forecast begin by Thursday and continue into
Friday. Very warm temperatures will be possible by Friday as 850
mb temperatures are progged to be 17 to 21C across the area.



Oklahoma City OK  43  66  48  70 /   0   0  10  30
Hobart OK         41  65  47  75 /   0   0  10  20
Wichita Falls TX  44  68  53  78 /   0  10  10  20
Gage OK           37  66  42  72 /   0   0   0  10
Ponca City OK     38  65  44  65 /   0   0  10  50
Durant OK         49  72  56  71 /   0  10  40  50




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