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Area forecast discussion
National Weather Service Norman OK
1215 am CDT Thu Mar 30 2017

Discussion...
the March 30-31, 2017 06 UTC taf discussion follows:

&&

Aviation...
ceiling restrictions with MVFR stratus will continue to persist
north and east of a line from near kgag/kwwr to kcsm to kokc/koun.
Some ceiling restrictions may make it as far south of a line from
khbr to klaw, but confidence is too low to include in tafs. A few
showers will be possible across north central Oklahoma until
approximately 09z.

Flight conditions are expected to transition toward VFR by
tomorrow afternoon except across northern Oklahoma where wrap-
around clouds are expected to persist until tomorrow evening.

Otherwise, west-northwest winds will shift to the north, then the
northeast and then east toward the end of the taf period.

Mahale

&&

Previous discussion... /issued 936 PM CDT Wed Mar 29 2017/

Update...
modification to pops, winds, temps for 1st period.

Discussion...
lowered pops most of the region with low pops continuing across
far northern Oklahoma tonight into tomorrow for possibility of
light wrap around precip. Will keep the stronger northwesterly
winds going for longer tonight given latest observation trends
and short term model output. Temps were only modified slightly to
align with observational trends.

Previous discussion... /issued 650 PM CDT Wed Mar 29 2017/

Discussion...
the March 30-31, 2017 00 UTC taf discussion follows:

Aviation...
ceiling restrictions with MVFR stratus will continue to persist
across the northern half of Oklahoma as wrap-around clouds rotate
around a cyclone. These lowered ceilings may make it as far south
as kokc/koun and khbr later tonight; however, currently expect VFR
conditions farther south. In addition, some showers may impact
kpnc this evening; however, confidence is too low to include in
tafs.

Otherwise, west-northwest winds are expected weaken after sunset
before increasing by tomorrow morning. Flight conditions are
expected to transition toward VFR by tomorrow afternoon except
across northern Oklahoma where wrap-around clouds are expected to
persist through the end of the taf period

Mahale

Previous discussion... /issued 323 PM CDT Wed Mar 29 2017/

Discussion...
primary forecast focus is on continued rain chances today and a
return chance for thunderstorms, possibly severe, on Saturday.

Just a note, quite a significant and fascinating heavy rain and
flooding event last night for western North Texas into
southwestern Oklahoma and central Oklahoma. The heaviest swath of
rain fell, generally, along and near the I- 44 corridor. I
haven't seen a stalled/backbuilding mesoscale convective system quite like that since
perhaps may 31, 2013 over the okc Metro. Looking back at the
ingredients, briefly this morning, how the event unfolded fits
quite well with corfidi's work with mesoscale convective system maintenance and motion,
1996, 1998, and 2003. As the low levels began to saturate, it
fostered an unfavorable environment for the development of
convective downdrafts, overall. This would suggest a lack of a
decent mesohigh formation, resulting in low forward propagation
as new development would nearly offset any propagation. This was a
fascinating case, and will be looked at much closer, as there are
several details i'm sure I glossed over here.

This afternoon, scattered showers and light rain continue to develop
across portions of western Oklahoma into the panhandles and western
Kansas. GOES-16 five minute water vapor imagery paints, quite
literally, a beautiful picture of the evolving progression of the
upper low. Of note on channel 10, low level water vapor, has been
the advancing dry slot from east of The Big Bend into eastern
Oklahoma. Oklahoma mesonet sites are picking up on this trend, with
recent dew points in the upper 40s cropping up along the I-35
corridor in far southern Oklahoma. With this in mind, confined the
best chances for rain to western and northern Oklahoma, where the
better isentropic ascent will reside as the upper low lifts
east/northeast through the evening and overnight.

Into tomorrow, the 500mb trough will continue to exit to the east,
finally sliding along the Ozark Plateau by midday. Low rain chances
will linger on the backside of the exiting trough, across north
central Oklahoma, through midday. Overall, still expect mostly
cloudy conditions for much of Oklahoma, as low clouds will trail the
exiting trough. Dry conditions can be expect through the remainder
of the day, with clearing in the afternoon helping temperatures push
back into the 70s across western North Texas. Upper level ridging
will increase into Friday across the Southern Plains. A weak surface
trough will position itself west-east across the region, with warm
southerly flow resulting in highs in the upper 70s and 80s across
texoma.

For Saturday, current water vapor shows a developing, off shore,
Pacific northwest low. Mid-range guidance remains in rather decent
agreement into the weekend. Expect the current Pacific low to dig
across the Cascades, into the intermountain west by Friday morning.
The 500mb trough axis will pivot over The Four Corners opening up
the Southern Plains to sufficient return flow from the Gulf through
Saturday morning. By daybreak, expect a defined dry line to be
shaping up along the Llano Estacado, with a potential for some
morning convection across northwestern Oklahoma, focused along a
pseudo warm front early. Through midday, the dry line will advance
eastward into western Oklahoma and western North Texas. Modest
instability, 800 to 1500 j/kg and shear will support scattered
thunderstorms, capable of severe hail and wind. Initially isolated
development, will merge into one or more complexes through the
evening, as storms move across central into eastern Oklahoma into
early Sunday.

Scattered showers and lingering thunder will hang around on Sunday,
as the parent, upper trough begins to swing and deepen towards the
Rio Grande Valley. Thunderstorms will remain possible through Monday
morning, across primarily southern into eastern Oklahoma, as the
upper trough finally lifts east by Monday night.

Kurtz

&&

Preliminary point temps/pops...
Oklahoma City OK 43 60 43 72 / 10 10 0 0
Hobart OK 42 67 43 74 / 10 10 0 0
Wichita Falls Texas 46 71 47 83 / 30 10 0 0
gage OK 38 63 39 66 / 20 10 0 0
Ponca City OK 43 51 39 66 / 30 30 10 0
Durant OK 47 65 46 80 / 10 10 0 0

&&

Oun watches/warnings/advisories...
OK...none.
Texas...none.

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