Area forecast discussion...updated
National Weather Service Norman OK
1030 am CDT Monday may 20 2013
Update...
severe weather is still expected through tonight. Increased probability of precipitation
through 12z Tuesday...and adjusted sky grids slightly. Please see
the discussion below.
&&
Discussion...
the latest information is indicating that we are setting up for
another significant severe weather episode across parts of central
into south-central into southeast Oklahoma this afternoon and this
evening. Although the 12z oun sounding indicates a rather
substantial capping inversion in place we still anticipate
thunderstorms to develop along and ahead of both the surface cold front
and dryline by early this afternoon.
Short range high resolution models are depicting two different storm
modes across Oklahoma today. From just north and east of the
Oklahoma City metropolitan storms are expected to be more linear and be
more of a hail and wind threat.
However...from near the okc metropolitan...southwest along and south of
the I-44 corridor...including all of south central and southeast
Oklahoma and perhaps parts of western North Texas from the Wichita
Falls area east...storms are expected to be more isolated and
discrete in nature. The winds fields will be very supportive of
supercell thunderstorms capable of producing strong...long-
tracked tornadoes as well as extremely large hail and damaging
straight-line winds. The area of south central into southeast
Oklahoma could see these storms linger throughout the afternoon
and much of the evening hours.
Probability of precipitation were increased across the central and eastern forecast area for this
afternoon/eve.
&&
Previous discussion... /issued 646 am CDT Monday may 20 2013/
Discussion...
aviation discussion for the 12z tafs is below.
Aviation...
MVFR ceilings are expected through 16-18z at kokc...koun...and
kpnc. MVFR conditions may redevelop anywhere south of khbr-
kpnc...but did not mention due to low confidence.
Added thunderstorms in the vicinity at kokc and koun 17-21z where confidence of occurrence
is moderate. Additional thunderstorms and rain may occur at other sites as well but
did not mention due to low confidence. If thunderstorms and rain directly affects
site...brief MVFR and lower conditions and variable gusty wind
would be possible.
A front near khbr-kpnc will slowly move south after 18z and bring
a wind shift from generally the south to north.
Mbs
Previous discussion... /issued 459 am CDT Monday may 20 2013/
Discussion...
severe thunderstorm potential this afternoon and evening with
very large hail and tornadoes is the forecast challenge of
the day.
Through 11 am this morning...capping should not allow for
much...if any storm development. Locations near and east of
Ponca City have the best shot for an elevated storm or two.
Confidence is high that another round of significant severe
thunderstorms will occur this afternoon into this evening in the
Storm Prediction Center moderate risk area. The environment this afternoon and evening
will be similar to yesterday with a few subtle differences
including slightly lower low level helicity and shear values and
slightly weaker capping.
It appears the highest chance area for severe storms this
afternoon and evening may be a bit farther south than
yesterday...perhaps near a Duncan to Pauls Valley to Seminole
line. The Oklahoma City area may be affected...particularly the
south side including Norman and Moore. First storms may develop a
bit earlier as a result of slightly weaker capping...1 to 3
PM...somewhere near or just east of I-44 from Lawton to Oklahoma
City. Based on latest hrrr/model guidance...storms would likely
begin as discrete supercells and may remain as this storm Mode...
though some models hint that storms may become more linear. Low
level shear is forecast to increase slowly throughout the
afternoon with an increasing chance for tornadoes...which may
large and long lived. Very large hail will be another concern with
any supercell. Storms may diminish or move into eastern Oklahoma
during the evening hours as the low level jet veers to the
southwest. The chances for severe will decrease tonight.
Locations northwest of I-44 have a much less chance for severe
storms through tonight. A front near a Frederick to Stillwater
line will move very little through early Tuesday morning.
Temperatures today should be a bit cooler than yesterday in
most locations.
On Tuesday...there is some potential for severe thunderstorms
along and south of the front...mainly southeast of an Ardmore to
Ada line...during the afternoon hours. Damaging wind and large
hail may be the main hazards. Confidence of severe is lower in
these areas.
Wednesday through Sunday...kept low chances...20 to 30 percent
for storms during most periods during this frame...though middle
level ridging should reduce storm coverage. A few severe storms
are possible nearly each day due to moderate to high instability
and abundant low level moisture. Temperatures near or slightly
below average on Wednesday are forecast to be above average by
the weekend.
Mbs
&&
Preliminary point temps/pops...
Oklahoma City OK 85 64 77 58 / 50 50 30 10
Hobart OK 94 60 83 56 / 20 10 20 10
Wichita Falls Texas 96 68 84 61 / 40 30 20 10
gage OK 84 53 83 48 / 20 10 10 0
Ponca City OK 83 60 78 53 / 30 40 20 10
Durant OK 88 70 81 64 / 10 60 60 40
&&
Oun watches/warnings/advisories...
OK...none.
Texas...none.
&&
$$
30/03
