348
FXUS65 KTWC 142159
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
259 PM MST Thu Nov 14 2024

.SYNOPSIS...Mildly warm temperatures are expected through Friday
across Southeast Arizona. A winter weather system is expected to
impact the area this weekend. Initially this will bring breezy
conditions Friday into Saturday, then cooler temperatures and
chances for valley rain and mountain snow showers Saturday night
into Sunday.

&&

.DISCUSSION...The upper air pattern is in a state of transition. A
ridge is now currently over the Great Plains and a trough is
beginning to move onshore on the West Coast. Even with the ridge
to the east we are still under positive height anomalies which
has led to the warmest temperatures of the month so far today.
Friday the upper level pattern across the country becomes more
amplified with a large-scale trough on the West Coast and a
large-scale ridge centered over the Midwest. The approaching low
will drop temperatures a few degrees Friday leading to high
temperatures a couple degrees above normal. It will also bring
breezy southwest winds 15-25 mph and gusts 25-35 mph. The
strongest winds will be along the international border and the
White Mountains.

Saturday the flow around the trough begins to split with a
shortwave breaking off and moving into Montana leaving the
southern part of the trough to begin to dig south. It becomes
closed off Saturday evening centered over southern California and
northern Baja. It then tracks eastward Sunday through Sonora.
Models have been consistent over the past 24 hours showing this
more southerly progression, lending confidence that this is the
track it will take. Still a little uncertainty with the speed it
moves through. As it travels through Mexico it becomes more
negatively titled, which speeds it eastward into west Texas and
Oklahoma by Monday. Strong southwest flow ahead of the trough will
advect moisture into northern Mexico and southern New Mexico. Southeast
Arizona will be on the western edge of the plume with the best
moisture in southeast Cochise County. This will lead to precip
chances starting Saturday night into Sunday mainly from Tucson
eastward. Because of the placement of the moisture plume QPF
amounts will be highest in southeast Cochise County ranging from
0.2"-0.5". Elsewhere from Tucson eastward rain amounts will
generally be less than 0.2". Any shifts of the moisture plume
northward will increase QPF for the rest of southeast Arizona.
Snow amounts will be light generally 1"-4" above 6000 feet with
the Chiricahuas on the higher end of that range. Temperatures will
run 10-15 degrees below normal Saturday into the middle of next
week.

After Monday the upper air pattern becomes more uncertain as
another shortwave moves through the region early next week. The
ECMWF ensemble is slower and stronger with this features while the
GEFS shows a much weaker and faster moving shortwave. Just enough
moisture will be left that if the euro is correct light showers
will be possible Monday night into Tuesday. The NBM is handling
this by introducing 15-30 percent PoPs from Tucson eastward during
this time frame. In the wake of the shortwave the upper air
pattern looks to become highly amplified again with a ridge over
the western U.S. and large closed low over the eastern U.S. This
would put Arizona under northerly flow aloft. This, combined with
the colder air behind the previous two systems, could lead to
possible freezing temperatures in the Tucson metro during the
middle of next week. NBM probabilities for 32 or below in Tucson
are around 50 percent Wednesday and Thursday mornings.

&&

.AVIATION...Valid through 16/00Z.
Skies will be SKC through the period. SFC winds will be out of
the west to northwest 8-12 kts with gusts to 18 kts for the
remainder of the afternoon, becoming light and terrain this
evening and overnight. Friday after 15/16Z an approaching weather
system will lead to winds out of the southwest 15-20 kts with
gusts 25-35 kts. The strongest winds will be along the
international border affecting KOLS and KDUG terminals. Aviation
discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Dry with afternoon temperatures slightly above
normal for this time of year through Friday. Winds are expected to
be light today, before becoming breezy Friday ahead of an
approaching winter weather system. Expect speeds 12-20 mph and gusts
to 30 mph with the strongest winds along the international border.
Valley rain and mountain snow showers will accompany this system
mainly from Tucson south and eastward Saturday night into Sunday.
Minimum relative humidities today and Friday will be around 10-15
percent in valleys and 15-20 percent in the mountains, increasing
significantly Saturday and Sunday where minimum RH values will be
30-45 percent in the valleys and 50-70 percent in the mountains.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Hardin

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