FXUS65 KTWC 021200
Area Forecast Discussion
National Weather Service Tucson AZ
500 AM MST Tue Jun 2 2020
.SYNOPSIS...Scattered thunderstorms this afternoon mainly near the
White Mountains, and a few afternoon thunderstorms may develop south
to southwest of Tucson. Dry conditions but with very hot daytime
temperatures will occur Wednesday into Thursday. A weakening
system should bring scattered thunderstorms Friday afternoon and
evening mainly east of Tucson. Dry conditions and seasonably hot
temperatures to prevail this weekend and early next week.
.DISCUSSION...The broad scale upper pattern early this morning over
the eastern North Pacific and central/western CONUS is defined with
a broad area of low pressure west of the southern California/Baja
California coasts, and another broad area of low pressure was over
the southern CONUS Plains. A generally light 700-500 mb flow regime
prevailed across this forecast area.
The various 02/00Z models continue to support the scenario of upper
ridge amplification over the southwest CONUS into Thursday.
Regarding precip potential, expect scattered showers/tstms this
afternoon and early evening across the White Mountains. Elsewhere,
isolated showers/tstms may develop this afternoon south to southwest
of Tucson. The bulk of any showers/tstms are expected to dissipate
shortly after sunset this evening followed by precip-free conditions
across much of the area late tonight through Thursday. The exception
is Wednesday afternoon when isolated thunderstorms may develop near
the White Mtns.
The main impact from the amplifying upper ridge will translate into
a few degrees of daily warming today into Thursday. The very hot
daytime temperatures Wednesday and Thursday combined with relatively
warm nighttime temperatures as prompted the upgrade of the inherited
Excessive Heat Watch to Excessive Heat Warning from noon Wednesday
to 8 pm MST Thursday. Please refer to AWIPS product PHXNPWTWC /WMO
header WWUS75 KTWC/ for detail.
The upper ridge axis is progged to shift eastward into West Texas
Friday as low pressure aloft moves northeastward into southern
California. The GFS/GEFS continues to be markedly more robust with
precip potential versus the ECMWF/ECENS. For forecast continuity,
have maintained isolated to scattered showers/tstms Friday afternoon
and evening east of Tucson. Precip-free conditions should occur late
Friday night and continue Saturday into Monday under a much drier
generally swly flow aloft regime. Daytime temperatures Saturday
through Monday will also trend quite close to seasonal normals.
.AVIATION...Valid through 03/12Z.
Scattered -TSRA/-SHRA this afternoon and evening mainly across the
White Mtns northeast of KSAD, and isolated -TSRA/-SHRA south to
southwest of KTUS. Brief wind gusts to 40 kts may occur with the
strongest tstms. Any -TSRA/-SHRA ending 03Z-06Z Wednesday.
Otherwise, FEW-SCT clouds 10k-15k ft MSL generally through valid
period, although BKN cloud decks at times this afternoon/evening.
Surface wind mainly under 12 kts, and favoring a wly/nwly component
this afternoon. The exception is near KSAD this afternoon where
nwly gusts near 25 kts should occur. Aviation discussion not updated
for TAF amendments.
.FIRE WEATHER...Scattered thunderstorms this afternoon near the
White Mountains, and isolated thunderstorms south to southwest of
Tucson. Dry conditions across much of the area Wednesday into
Thursday, although a few thunderstorms may occur Wednesday afternoon
near the White Mountains. Isolated to scattered thunderstorms return
Friday afternoon and evening, especially east of Tucson. Gusty and
erratic winds will occur at times due to thunderstorm outflows, and
the potential exists for increased fire starts due to lightning. Dry
conditions will then prevail late Friday night into early next week.
Aside from thunderstorm wind gusts, 20-foot winds on Friday will be
gusty at times mainly from the southwest. 20-foot winds will
generally be terrain driven under 15 mph at other times.
Excessive Heat Warning from noon Wednesday to 9 PM MST Thursday
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