873
FXUS65 KTWC 120924
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
224 AM MST Mon Apr 12 2021

.SYNOPSIS...A dry weather pattern will continue this week with
afternoon breezes each day. Daytime high temperatures will start off
the week above normal, lowering to near normal by the end of the
work week.

&&

.DISCUSSION...Breezy westerly zonal flow will be in place to start
this week. Heights/thicknesses support afternoon highs of 6-9
degrees above normal today and Tuesday. The majority of the high
clouds in place will shift east of the forecast area this morning,
with mostly sunny/clear skies expected through Tuesday.

Deterministic model runs of the GFS/ECMWF and ensemble members
(including WPC Cluster Analysis Tool) are all in excellent agreement
through day 4, or this upcoming Thursday. They show a disturbance
dropping southward out of western Canada into the Great Basin late
Tuesday and remaining nearly stationary into Thursday. This system
will remain to far north to bring any precipitation to southern
Arizona. However, it will tighten gradients across the area,
resulting in breezy to windy conditions Tuesday through Thursday.
Expect increasing high clouds across southeast Arizona Wednesday and
Thursday. Heights/thicknesses also lower over this time frame, with
daytime highs lowering to near normal Thursday and Friday.

The deterministic models and ensembles begin to diverge on solutions
by next weekend (days 6/7), with some members dropping a piece of
energy through Arizona, while others keep this feature east of the
area. At this time, the GFS appears to be an outlier in regards to
actually spinning up a weak closed low across central Arizona late
Saturday into Sunday. The strength and amplitude of an upper ridge
developing off the west coast during this time frame will be
critical in the actual placement and strength of this feature. Have
elected to introduce slight chance pops for next Sunday for the
White Mountains, which matches up well with the surrounding offices.
Attm just have a slight chance of showers, but depending upon timing
and strength of the disturbance, there may be the potential for some
thunderstorms as well.

For now, the main weather concern this week will be the potential
for breezy to windy conditions and the near critical to critical
fire weather conditions outlined in the fire weather section below.

&&

.AVIATION...Valid through 13/12Z.
Clouds will clear out this morning then SKC for the rest of the
period. Southeast winds 5-10 kts this morning becoming southwest 12-
18 kts with gusts 20-26 kts this afternoon and early evening. After
about 13/03Z winds calm down again to 5-10 kts. Aviation discussion
not updated for TAF amendments.

&&

.FIRE WEATHER...Expect dry conditions through the upcoming work
week, then a slight chance of rain in the White Mountains Sunday.
Breezy winds will continue each afternoon and early evening. Expect
the strongest winds Tuesday when 20-ft speeds will be 15 to 20 mph
with gusts 30 to 40 mph, especially south and east of Tucson.
Southeast Cochise County could see brief critical fire weather
conditions Tuesday afternoon. Minimum RH values will continue to be
low, in the single digits and lower teens. Temperatures will remain
above normal into at least Wednesday, then closer to normal late
next week.

&&

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

&&

$$

Discussion...Zell
Aviation/Fire Weather...Hardin

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