Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Tulsa OK
528 PM CST Wednesday Dec 18 2013
concerning taf sites ktul/krvs/kbvo/kmlc/kxna/kfyv/kfsm.
VFR conditions will prevail overnight. A strong low level jet will
develop...resulting in low level wind shear at kfsm overnight into Thursday
morning. Increasing low level moisture will result in MVFR
ceilings developing Thursday morning. The clouds will likely
scatter out at the northeast Oklahoma sites during the afternoon.
South winds will gust to around 25 knots at most sites during the
Previous discussion... /issued 312 PM CST Wednesday Dec 18 2013/
one more warm day before the bottom drops out. Southerly surface will
continue into Thursday...ahead of a cold front that will move into
central Kansas during the afternoon. Increasing low-level moisture will
result in areas of stratus for the area...although still expect
temperatures to warm back well into the 60s. The fire danger will
remain high again on Thursday...although afternoon relative humidity values should
be higher than today.
The cold...but very shallow...airmass will slide into NE OK later
Thursday night and should be south of I-44 by Friday morning. Lift
over the top of the shallow cold dome should lead to areas of
drizzle/freezing drizzle to the north of the front...although amounts
will be light. Even so...a thin glazing on elevated surfaces and
overpasses will be possible. The cold front will likely stall in the
higher terrain of northwest Arkansas and far southeast OK...with temperatures remaining nearly
steady across NE OK through the day.
Biggest question with the remainder of the forecast is how quickly
(or slowly) the cold air erodes as the low-level warm air advection increases over
the weekend. The NAM and CMC remain the coldest with the near surface
temperatures...although the latest 12z European model (ecmwf) is also a bit colder than its
previous runs. That said...will keep the best chances of freezing
rain Friday night northwest of I-44...with a transition zone along the I-44
corridor...and all rain farther S. The situation becomes more
uncertain later Friday night into Saturday as the precipitation
rates increase. There is the possibility...and i've see it
before...where warmer air aloft is dragged back down to the surface.
So needless to say...the confidence level in precipitation type and
placement across NE OK Friday night into Saturday remains low.
The tremendous isentropic lift across the region will result in
heavy rainfall across southeast OK into northwest Arkansas late Friday night into
Saturday...where 2 to 3 inches of rain (and locally higher amounts)
will be possible. Should also see thunderstorms develop Saturday
afternoon into the evening across southeast OK/western Arkansas as unseasonally moist
low-level air is drawn back north into this area. Ffg values are rather
low in a few locations (3hr values around 2-2.5 inches)...so will
certainly need to monitor the flooding situation.
The compact upper low across the southwestern states will eject NE across OK
and into MO Saturday night. The heaviest rainfall will shift east of the
region at this time...although a precipitation area associated with
the upper low is expected to transition to snow overnight across NE
OK...and eventually move into northwest Arkansas early Sunday. Could see some
light accumulations along and north of I-44.
As mentioned...forecast confidence in precipitation type and placement
remains low. The forecast will continue to be refined over the next
few days. Stay tuned.
OK...red flag warning until 6 PM Wednesday for okz054-okz059.