Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Norman OK
800 PM CST Thursday Dec 5 2013
update to probability of precipitation through 06z...
temperature forecast remains on track with respect to current observation
trend. Made updates to probability of precipitation/weather to bring more in line with radar
trend and reports. For the moment...most if not all precipitation has
ceased across west central and northwestern OK... including the okc metropolitan.
A few flurries will linger through the late evening hours across
the metropolitan and locations north/NE through Guthrie and up to Stillwater.
The heaviest band of wintry precipitation continues to slowly move east/NE
across south central/southeastern OK. Expect most of this activity to be
sleet... with some areas of freezing rain along the Red River Valley North/NE
into far eastern OK. This band/area of ice pellets/freezing rain will continue through
the evening and persist through the overnight.
Made no changes beyond 06z as confidence remains in a decent band
of snow developing overnight from SW OK/western North Texas newrd across
Oklahoma. Expecting additional accumulations across central OK
from 2 to 4 inches... with locally higher amounts brining totals
near 6 inches.
Previous discussion... /issued 500 PM CST Thursday Dec 5 2013/
light precipitation may continue through the evening hours with most at the taf
sites seeing snow/sleet. Mfvr ceilings/visibilities may drop into
the IFR Cat overnight as band of heavier snow redevelops across the
area. Most precipitation will end by 15-18z with return to MVFR conditions.
Previous discussion... /issued 336 PM CST Thursday Dec 5 2013/
a band of moderate sleet and snow continues to move northeast over
the i44 corridor...with freezing rain and sleet southeast of it
across S/southeast OK. Lift and saturation were likely underestimated
with this first shortwave trough yesterday by the nwp
models...which has resulted in higher impacts earlier in the day.
Several reports and images suggest snow/sleet totals around 1
inch already across the okc metropolitan. Travel has become very hazardous.
This first round of precipitation will slowly come to an end as the wave
shifts eastward...with the heaviest snow/sleet ending for the okc
metropolitan within the next 30 mins to an hour. Sporadic light snow and
sleet will continue through the overnight hours along and west of
i35...while heavier precipitation remains over eastern and southeast OK. This is
where significant icing is still expected...although ice
accumulation amounts may remain slightly lower than anticipated if
moderate precipitation rates can continue (diabatic cooling). All
headlines will remain in effect.
Very late tonight through early tomorrow morning...another round
of snow is expected to first develop over SW OK/west North Texas around
midnight and proceed northeastward near or just west of where the
first round of precipitation occurred by around 2 to 5 am. The
culprit...the main middle to upper shortwave trough and the rrq of an
upper jet traversing the plains. This zone of lift has been very
consistent within the nwp models over the last couple of
days...especially the GFS. However...most have appeared to narrow
this zone of both lift and moisture (some drier air tries to move
in) through the dendritic growth zone. It will be difficult to pin
down where the heaviest bands will develop...but the previous
appears likely over portions of west central/central/north central
OK including the northern metropolitan where an additional 2 to 4 inches
(locally more) could fall by sunrise. A few flurries could
continue through the late morning from i35 eastward...but
subsidence/much drier middle to upper air will quickly accompany the
passage of the trough and the snow will rapidly end as early as
lunchtime for the majority of our forecast area.
The main impact heading into the weekend will be very cold
temperatures. On Saturday morning...surface ridge axis will slip into
central and southwest Oklahoma. As winds become light or go calm
overnight...rapid radiational cooling should allow temperatures
to plummet into the single digits and low teens. Wind chills will
range from -5 to -13 degrees. Another upper level storm system
will move across the Southern Plains Saturday and Saturday
night...bringing low chances for snow. Some light accumulation may
occur...but should generally remain below an inch. Any snow should
end by Sunday evening. Highs Saturday and Sunday will only climb
into the low to middle 20s...and sub freezing temperatures will
continue both day and night well into the middle of the week. A
very slow warmup is expected by Wednesday...our next potential
above freezing day. Otherwise...the remainder of the week looks to
Preliminary point temps/pops...
Oklahoma City OK 18 22 5 20 / 100 60 0 10
Hobart OK 15 22 5 18 / 90 30 0 10
Wichita Falls Texas 20 25 9 23 / 80 50 0 20
gage OK 8 21 1 23 / 50 10 0 10
Ponca City OK 13 24 4 25 / 60 40 0 0
Durant OK 22 26 13 26 / 90 70 0 20
OK...Winter Storm Warning until 6 PM CST Friday for okz016>020-
Winter Weather Advisory until 6 PM CST Friday for okz004>015-021.
Ice Storm Warning until 6 PM CST Friday for okz032-041>043-
Texas...Winter Storm Warning until 6 PM CST Friday for txz083>089.
Ice Storm Warning until 6 PM CST Friday for txz090.