Area Forecast Discussion
Issued by NWS Tulsa, OK

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FXUS64 KTSA 251118

518 AM CST WED NOV 25 2015

For the 12Z TAFs, MVFR ceilings prevail at all sites this morning.
Ceilings will continue to fall today with IFR conditions expected
later this morning at many sites. Gusty southerly winds will
continue. Light drizzle may develop across a portion of the area
later today, but due to low probability have not included in any




The main forecast challenges continue to focus on the heavy
rain/flood potential late this week...and winter weather potential
to start the weekend.

Very amplified upper air pattern is already taking shape over
western NOAM this morning...with ridging over the northeast
Pacific nosing well up into AK...Yukon and the Northwest
Territory. Downstream from the ridge...a large and rather potent
PV anomaly was dropping down toward the Great Basin...embedded
within a larger scale positive tilt longwave trough. This type of
pattern tends to be very messy over the Plains during the cold
season...and this system will be no different. Shallow cold air
will wedge its way south as a strong cold front...which will
plunge south and east across our area Thanksgiving night.
Meanwhile...the upper pattern favors considerable moisture return
from the south...with forecast PW values at more than 3 times
climatology for this time of year. The front will act to lift this
plentiful moisture...setting the stage for bands of heavy rain and
possible flooding impacts. The heaviest rains are most likely to
occur Thanksgiving night across NE OK over into NW AR from the
I-44 corridor...shifting south on Friday. Another round of precip
is forecast to slide across the southern areas again on
Saturday...with some injection of moisture from the Pacific
tropical system. Rainfall totals in the 4 to 8 inch range are
possible...with the heaviest amounts along and south of I-40 thru
Saturday. A flash flood watch will be issued from the I-44
corridor south Thursday night into Friday.

We usually can`t have a discussion about shallow cold air without
talking about some winter weather. As we get closer to this
event and it is now within the time range of the NAM...a model which
has historically done better with shallow cold air than the global
spectral models...a trend toward cooler surface temps is evident
across NE OK Friday into Saturday. A well established warm layer
aloft will ensure that all precip is liquid...just a matter of
where the surface freezing line sets up. As it looks with the 00z
runs of the NAM and the ECMWF...which has trended colder as appears that some light icing potential exists for
Pawnee and Osage counties to the NW of Tulsa Friday night into
Saturday morning. Impacts to bridges will probably be what to
watch surface temps will be borderline freezing. Icing
potential will be much greater farther to the west and north.
Temps are forecast to rise above freezing across all of eastern OK
by Saturday afternoon.

The bulk of the rain shifts east by Sunday...with some potential
for light rain or showers continuing thru Monday night with the
western CONUS upper low taking its time to move east across the



.TSA Watches/Warnings/Advisories...
OK...Flash Flood Watch from Thursday evening through Friday afternoon
     for OKZ049-053-057-058-060>076.

AR...Flash Flood Watch from Thursday evening through Friday afternoon
     for ARZ001-002-010-011-019-020-029.



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