851
FXUS65 KTWC 111018
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
318 AM MST Tue Mar 11 2025

.SYNOPSIS...

An active weather pattern is expected to impact southeastern
Arizona this week as a series of low pressure systems move through
the area today through tonight and again Thursday into Friday.
Breezy to locally windy conditions are expected this afternoon and
evening, especially near the International Border. A front will
then bring widespread rain showers and mountain snow tonight. Much stronger
winds with the potential for blowing dust and another round of
widespread valley rain and mountain snow will accompany the second
system Thursday into Friday.

&&

.DISCUSSION...

A pair of mid-level shortwave troughs are expected to impact
southeastern Arizona this week, the first today through tonight
and the second Thursday into Friday. In the upper levels early
this morning, a closed low was spinning over the eastern Pacific
just off the southern California coast, while a deeper low with a
potent associated jet streak was over the Gulf of Alaska. On GOES
and ALPW products both circulations feature healthy precipitable
water values, which will deliver precipitation chances across
southeastern Arizona with both passages.

Today, a 90 knot jet streak associated with the first circulation
will cross northern Sonora as the upper low opens and becomes more
progressive. As a pressure gradient tightens through the lower
levels in response to the approaching jet streak, increasing southwesterly
winds will develop, especially across southern areas including
Santa Cruz and Cochise Counties. 15-25 mph winds with gusts to 40
mph are expected from late this morning through this evening.
Patchy blowing dust will be possible in areas normally prone to
blowing dust.

The trough`s low-level frontal passage under strong upper level
ascent associated with the left exit region of the jet streak
will produce a band of showers that will stretch from central
through southern Arizona. This coupling of forcing will likely see
brief periods of moderate to heavy rainfall within this line of
showers, producing a quick tenth to three tenths of an inch under
stronger showers. 00Z HREF indicates an isolated chance of up to a
half inch, likely where multiple showers pass over the same area.
While impacts should be minimal, minor ponding may occur under
more persistant activity. Under this modestly convective activity,
periods of heavy snowfall rates will be possible in locations
above 7000 feet. Generally 2 to 4 inches will be a safe bet for
most of these mountain locations, however the possibility of
multiple rounds of heavy snowfall showers can`t be ruled out.
Though not currently in the forecast products, an outside chance
of lightning exists under the center of the upper level
circulation from Pinal and central Pima westward.

Thursday, a progressive and higher amplitude trough arrives out of
the original Gulf of Alaska circulation. Again a potent jet streak
is expected to cross the area, this time arriving with colder
temperatures in the low to mid levels. With this trough expected
to arrive with deeper height anomalies and a stronger pressure
gradient, windy conditions are expected Thursday into Friday as
the trough approaches and crosses. As guidance such as NAEFS
climatology and the ECMWF Extreme Forecast Index is producing high
end values near their maximum, it looks like at least a Wind
Advisory will be needed, or potentially a High Wind headline if
ingredients line up. The threat of potentially dense blowing dust
will likely arrive with strong winds with widespread 40-55 mph
wind gusts. As mentioned, the potential for higher end wind gusts
will need to be monitored, especially in Cochise County where
strong southwest flow can produce severe non-thunderstorm wind.
Initial showers moving in could also bring strong winds aloft
down to the surface.

Widespread rain and mountain snow will arrive Thursday into Friday
with this second system. As the vort max and jet streak passage
looks to be a bit further north, heaviest precipitation potential
will generally be north to northeast of Tucson. Generally forecast
rain amounts range from a quarter to a half inch, but potential
lower end amounts fall to just under a tenth while higher end
(especially north and northeast of Tucson) may exceed three
quarters of an inch. Forecast water equivalent precipitation in
mountain locations north and east of Tucson range from three
quarters of an inch to near an inch, producing 4 to 8 inches in
the Catalina and Pinaleno mountains above 6000 feet and 6 to near
12 inches in the White Mountains. Some light snow may drop further
down in elevation after heaviest precipitation passes Friday
morning, especially near valley floors east of Tucson at 4000-4500
foot elevations.

With cool, northwest flow aloft in place behind the exiting trough
Friday, well below normal highs and breezy conditions are
expected. Highs in the mid to upper 50s across desert locations
are likely. Temperatures should quickly rebound by Sunday and
Monday as ridging overtakes the region. Another trough impacting
the region in some fashion looks reseasonable based on most
ensemble model solutions by next Tuesday or Wednesday.

&&

.AVIATION...Valid through 12/12Z.

SKC until this afternoon when SCT-BKN cirrus increases ahead of an
incoming weather system. Surface winds will become south to
southwest 10 to 20 kts this with gusts to 35 kts possible along
the International Border (mainly impacting the KOLS and KDUG
terminals. Rain showers and lower ceilings are expected to spread
from west to east after 12/00Z, impacting KTUS-KOLS starting
12/05Z-12/09Z and KSAD-KDUG starting 12/08Z-12/12Z. 3k-5k ft
ceilings are likely with embedded MVFR, especially in shower
activity. Wind overnight will remain south to southwesterly and
become 10-15 kts, though occasional gustiness possible with rain
showers.

&&

.FIRE WEATHER...

The first of two weather systems this week will begin to impact
the region today, initially with increased southwest winds of
15-25 mph and gusts to 40 mph this afternoon. Winds will likely be
strongest near the International border from Santa Cruz through
Cochise counties. With dry relative humidity values in the 8 to 14
percent range, near critical fire weather conditions are likely.
Critical fire weather conditions will be more limited as coverage
of strongest winds looks inconsistent, outside of a couple hours
of critical conditions in southern areas of Fire Weather zones 151
and 152. Then an area of rain showers and mountain snow will move
through southeast Arizona tonight. A second system is expected to
impact the region beginning Thursday, bringing stronger southwest
wind and then widespread chances for rain and mountain snow.
Minimum relative humidities are expected to be high enough
Thursday to prevent greater fire weather concerns.

&&

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

$$

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Aviation...Edwards
Fire Weather....Edwards

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