Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Amarillo Texas
1147 am CST Wednesday Nov 25 2015
VFR conditions expected to continue through daylight hours and
through a good part of the night. Cold front arrives in northern
sections tonight...with conditions deteriorating quickly thereafter.
At northern terminals...IFR ceilings and visibilities are expected
with light liquid precipitation and the potential for thunderstorms
through the morning.
At kama...pre-frontal moist southerly flow will bring onset of IFR
ceilings before daybreak. Rain and occasional thunderstorms
expected through the morning.
Previous discussion... /issued 551 am CST Wednesday Nov 25 2015/
southwest winds will pick up into the 11 to 16 knot range by late
morning. Winds will back some this evening. Then a strong Canadian
cold front will move south across the dht and Guy taf sites switching
their winds around to the north and northeast. Low clouds in the MVFR
range are expected to fill in behind the front. Low clouds and fog
may fill in across the Ama taf site ahead of the front early
Thanksgiving day. For now have taken conditions down into the MVFR
range. However...conditions may get worse than that...so expect
updates through the day.
Previous discussion... /issued 506 am CST Wednesday Nov 25 2015/
overall thinking for evolution of winter storm to impact the Texas
and Oklahoma panhandles through the weekend remains on track. Slight
tweaks to probability of precipitation...qpf...ice/snow accumulations...and weather grids
based on latest trends. Warm weather today and ahead of a cold front
tomorrow...with weather turning cold and wet for the end of the week.
See below for more details. Remember details of the forecast are
likely to change over the next few days...so be aware of any updates
or new watches...advisories...or warnings issued for the area.
Short term...today through Thursday...
Canadian cold front stretched from northwest Minnesota southwestward
across southeast North Dakota through western South Dakota through
central Wyoming into northwest Utah. This cold front will continue
to push southward today reaching the Oklahoma Panhandle by late this
evening. Meanwhile a large upper level positively tilted trough
stretched from near San Francisco northeastward into south central
Canada early this morning.
As this upper level trough slides off to the southeast the cold
front will get a shove to the south and it should clear the
panhandles by late Thursday afternoon. A strong southwest flow aloft
with embedded short wave troughs will be found over the panhandles
tonight into Thursday. Low level moisture will return ahead of the
front. Shear will also increase as the upper trough edges closer. All
of these ingredients should come together to help produce showers and
thunderstorms across much of the panhandles late tonight and
Thursday. A severe storm can not be ruled out...but it looks like
most of them should remain below severe limits. As the cold air
deepens Thursday afternoon we may see some of the rain switch over
to a wintry mix in the far northwest.
Long term...Thursday night through Tuesday...
With the cold front clearing the southern Texas by Thursday
evening...a shallow cold airmass is expected to remain in place
across the panhandles through Saturday. Aloft...an upper-level low
pressure system is forecast to cut off from the main flow on Thursday
and wobble over the Great Basin. Also a ridge of high pressure
will be centered over the Gulf of Mexico...helping to steer warm
moist air from the eastern Pacific over the cold surface airmass.
Chances for precipitation from Thursday night through Saturday remain
high...as a rich supply of moisture and lift ahead of the upper low
will persist through then.
Regarding precipitation type...model forecast soundings disagree over the
strength of the warm layer atop the surface airmass...so have
generally kept a mix of wintry precipitation across most of the panhandles.
NAM falls on the warmer side...with the GFS keeping a cooler profile
throughout. Given the synoptic setup with persistent southwest flow
in the middle levels...have favored the warmer solution and left
predominantly freezing rain across all but the far northwestern Texas
Panhandle and western/central OK Panhandle. At the onset...moisture
will not be present in the dendritic growth zone...meaning any precipitation
will be either rain or freezing rain. Then as we progress into late
Thursday night...the middle levels of the atmosphere should saturate
and sleet or snow will begin to mix in /especially with any
convective showers/. Friday during the day is tricky...as precipitation type
will largely depend on how warm and deep the warm layer remains and
how saturated the middle levels remain. Snow most likely across the
northwest and freezing rain/sleet most likely across the southeast.
By Saturday morning...middle levels look to begin drying out...meaning a
return to light freezing rain or freezing drizzle as the best
moisture pushes east of the panhandles. Light showers could continue
across the east into Saturday night.
Total ice accumulations around one half inch could be possible
across the southeastern half of the Texas Panhandle. Accumulating
sleet and snow on the order of 3 to 5 inches could be possible
across the western OK Panhandle and northwest Texas Panhandle. Central
portions of the Texas Panhandle will see some mix of each. Regardless of
the exact type and timing...hazardous driving conditions are likely
to develop across the area late Thursday night/Friday morning and
persist into Saturday. Plan accordingly if travel is necessary and be
prepared for icy driving conditions. Stay up to date with the latest
weather forecast and conditions...as revisions to the forecast are
possible as this system evolves. Milder weather should return for
early next week.
Texas...Winter Storm Watch from Thursday evening through Saturday
morning for the following zones: Armstrong...Carson...
OK...Winter Storm Watch from Thursday evening through Saturday
morning for the following zones: Beaver...Cimarron...Texas.