Area Forecast Discussion
Issued by NWS Amarillo, TX

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097
FXUS64 KAMA 012326 AAA
AFDAMA

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
526 PM CST Thu Dec 1 2016

.AVIATION...
Light northeast winds should prevail at speeds under 15 knots through
this forecast. Cloud cigs should lower Friday afternoon, but they
should remain VFR. There is a chance for some showers Friday
afternoon, but if they affect a TAF site, conditions are expected to
remain VFR.

&&

.PREV DISCUSSION... /Issued 354 PM CST Thu Dec 1 2016/

DISCUSSION...

The focus will be on the weekend system beginning Friday night and
going through Saturday...perhaps lingering around until early Sunday
morning. A lot of uncertainty at this time, but I hope to convey
confidence where it exist, as well as which variable(s) will be key
going forward.

A few things to keep in mind...It will only take a degree to perhaps
a few degrees in difference at certain levels aloft and/or the
surface for this forecast to vary significantly. The current
forecast is the most likely scenario. Localized higher amounts of
snowfall are certainly possible. The Oklahoma Panhandle and
northwestern parts of the Texas Panhandle have the best chance for
accumulating snowfall. Temperatures at the surface will also impact
snow accumulation, which may make it difficult to discern how much
snowfall actually occurred once the event is over.

The factors that were weighted most in this forecast where:

1) QPF
2) Probability for precipitation
3) Low level temperatures
4) Trends, Analogs, and Reforecast/Reanaylsis of past events with
   similar setups.

Note: Analogs were from St. Louis Universities CIPS guidance, and
the Reforecast was from NCEPs global ensemble (GEFS).

QPF has been pretty consistent with the majority to our southeast,
where little to no snowfall is expected due to low level temperatures.
Friday night is our best chance for snowfall; however, higher QPF is
not lined up with the colder temperatures to produce snowfall. That
is probably the biggest consideration at this time, but is also the
one variable which will be impacted the most with variations of
surface/low level temperatures. This system is plentiful with
moisture to our southeast, so any snowfall that does occur within the
heavy QPF field has the potential to produce greater snowfall
amounts. The majority of the forcing will be from isentropic lift,
and that being said overall lift is not that impressive, especially
in the dendritic growth zone. Synoptically speaking this is not the
best set up for us to receive accumulating snowfall. Fortunately we
have another 24 hours to analyze the system as it approaches closer.
Stay tuned for updates/changes to the forecast.

Overall confidence is not high with this forecast. Too many
uncertainties exist with this forecast that could produce a
different output. Trends, especially with temperatures and QPF, have
led to what is currently forecast, and I believe its the most likely
scenario. The temperature profile coupled with the QPF amounts
Friday night will be the most important factor to watch going
forward. Probability for precipitation is pretty high for this event
and has the highest confidence. Precipitation is going to occur, but
the precipitation type is still a little uncertain in some areas.

Guerrero

&&

.AMA Watches/Warnings/Advisories...
TX...None.
OK...None.

&&

$$

15/3



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