FXUS65 KTWC 141642

Area Forecast Discussion
National Weather Service Tucson AZ
940 AM MST Fri Aug 14 2020

.SYNOPSIS...An extended period of excessive heat can be anticipated
into next week as high pressure aloft strengthens over the
region. There might be a break in the heat from time-to-time as a
chance of showers and thunderstorms remain in the forecast. The
weather pattern will become favorable next week for a daily dose
of thunderstorms more typical of the monsoon season.


.DISCUSSION...Satellite was showing a batch of cloudiness across
southeast Arizona this morning, with radar detecting a few light
showers. This cloudiness and associated light showers will be a
factor on whether the projected high temperatures can be reached or
not. Otherwise, the forecast looked in good shape with additional
development in showers and a few thunderstorms expected this
afternoon. Please refer to the additional sections in this product
for more details.


.AVIATION...Valid through 15/18Z.
FEW-BKN clouds 15k-20k ft MSL this morning becoming 10k-15k MSL this
afternoon into the evening. Isolated to scattered -TSRA will be
possible mainly south of KTUS during the afternoon and evening.
Strong and gusty winds will be possible in the vicinity of storms.
Sfc winds will be out of the southeast this morning becoming
north/northwest this afternoon and evening 5-10 kts. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Isolated to scattered afternoon and evening showers
and thunderstorms are forecast the next 7 days, primarily south and
east of Tucson. Saturday and Sunday will likely see the greatest
coverage of storms. Temperatures will remain hot and moisture
generally drier compared to average. 20-foot winds will follow
typical diurnal patterns at less than 15 mph outside of any
thunderstorm wind gusts. Daytime humidity will generally be in the
15 to 25 percent range in the valleys and 20 to 30 percent in the
mountains with moderate to good overnight recoveries.


.PREV DISCUSSION (329 AM MST Fri)...Strong high pressure currently
located across southern AZ/NM will slowly move northwest toward the
Great Basin through the weekend. This will allow more of a east to
northeast flow beginning today for extreme SE AZ. Almost all CAMS
depict scattered to perhaps likely showers and thunderstorms
initiating across Cochise County and moving southwest through Santa
Cruz County. Instability is forecast to be sufficient with enough
flow for possible brief organization as storms move southwest into
Santa Cruz County. Strong to perhaps an isolated severe thunderstorm
cannot be ruled out before moving into northern Sonora. The main
threat will be strong, potentially damaging winds. Elsewhere,
thunderstorm coverage will be isolated as the best chances will be
across Santa Cruz and central and southern Cochise County.

By Saturday and Sunday, the high pressure continues to settle into
the southern Great Basin with a continuation of much above average
to near record daytime highs. The one caveat will be afternoon
showers and thunderstorms, which could keep temperatures down a
degree or two from the current forecast. Nonetheless, this will
still be sufficient for the Excessive Heat Warning to continue. With
the high pressure to the north, flow will strengthen from the
northeast. As the flow strengthens, additional moisture will move
into southern AZ. These days will need to be watched, as sufficient
moisture and instability will be in place for strong thunderstorms.
On both days, models are indicating storms firing off the Rim
Country and higher terrain north and east of Tucson. Storms then
move southwest through the late afternoon and early evening in what
could be a rim shot. This has been a consistent trend in recent
model runs, therefore confidence is increasing of two potentially
active days. With increasing confidence of this scenario, POPs were
raised above consensus. The main threat with these thunderstorms
would be strong and potentially damaging winds.

By the early to middle portions of next week, temperatures will
remain well above average. The Excessive Heat Warning is set to
expire Monday evening, but we will need to watch how much monsoonal
moisture and how the thunderstorm coverage materializes.
If we do not get adequate moisture and thunderstorm coverage, the
Excessive Heat Warning could sadly be extended into Wednesday.


   Excessive Heat Warning until 8 PM MST Sunday for AZZ503-509.

   Excessive Heat Warning until 8 PM MST Monday for AZZ501-502-



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NWS TWC Office Area Forecast Discussion