Scientific Forecaster Discussion
fxus65 kfgz 072148
Area forecast discussion
National Weather Service Flagstaff Arizona
248 PM MST Sat Dec 7 2019
Synopsis...a Pacific weather system will bring rain and mountain
snow showers back to northern Arizona tonight through Monday. Dry
and mild weather will return on Tuesday and then last through most
of next week.
Discussion...high pressure was heading to the east during the
afternoon hours with a Pacific trough and associated cold front
fast approaching from the northwest. In advance of the trough
moisture in the low to mid levels was rapidly increasing evidenced
by the thickening and lowering clouds observed through mid
Overnight...moisture will continue to increase with rain and high
elevation snow showers spreading from southwest to northeast
across most of northern Arizona from late this afternoon through
tonight. The snow level will range from near 8,500 feet across
northwest Arizona to around 10,000 feet over the White Mountains
of far east-central Arizona.
On Sunday and Monday...the current trough will produce breezy and
cooler weather along with rain and high elevation snow. Look for
another relatively mild system with the snow level starting out in
the 8,500 ot 10,000 foot range. A decent moisture tap has been
established with this system the result being precipitation
amounts generally along the lines of 0.25" to 0.75" inches. Along
the Mogollon Rim, higher mountain peaks and other southwest facing
slopes potentially over an inch of in terms of liquid
precipitation where upslope flow will be enhanced. Streams and
rivers south of the Mogollon Rim across Yavapai and Gila counties
will likely be on the rise again later on Sunday. That will be
something we'll keep an eye on. The coldest air arrives with a
cold front Sunday night but precipitation will be winding down
with only light snow accumulations below 7,500 feet somewhere in
the range of "i saw some snow falling" to 2 inches by Monday
morning. Up to a foot of snow accumulation will be possible over
the higher mountains such as the San Francisco peaks, White
Mountains, Kaibab Plateau and portions of the Chuska Mountains
where more of the current system will come in the form of snow. The
threat of showers will linger on Monday with even a bit of a
convective uptick Monday afternoon with daytime heating as some
moisture and colder mid-level temperatures linger over Arizona.
From Tuesday Onward...generally warmer and drier weather will
return, lasting through much of next week. High level clouds,
quite thick at times, will continue to stream across the area as
series of weak weather systems brush Arizona. Pressure gradients
will remain weak for light winds.
Aviation...for the 00z package...until 06z...look for areas of MVFR
ceilings with isolated to scattered light showers west of a kpga-
kpan line. After 06z and through the day Sunday...widespread rain
showers will bring MVFR and localized IFR conditions to northern
Arizona. Snow level generally 8000-9000 feet above sea level.
Aviation discussion not updated for taf amendments.
Fire weather...expect rain and some mountain snow on Sunday and
Monday. Ventilation will be limited to marginal or fair each
afternoon due to shallow mixing.
Tuesday through Thursday...dry conditions Tuesday through Thursday.
Temperatures returning to seasonable levels. Light winds.