Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 221003

Area Forecast Discussion
National Weather Service Tucson AZ
300 AM MST Mon May 22 2017

.SYNOPSIS...Dry conditions will persist this week with above normal
high temperatures continuing through Thursday. Tuesday and Wednesday
will be warmest days. Breezy conditions and fire weather concerns
will occur Thursday and Friday.


.DISCUSSION...IR satellite imagery this morning showed clear skies
over southeast Arizona. Surface temperatures were running 5-10 degs
warmer than 24 hours ago after daytime highs reached into the mid
and upper 90s for many valley locations Sunday afternoon. A weak
shortwave passing across the area today may produce a few afternoon
buildups across the White Mountains, but the bulk of moisture and
any precipitation should remain east of the AZ/NM border.

Dry NW flow aloft will dominate into mid-week as ridging builds in
from the west. This will result in mostly clear skies and above
normal temperatures, with Wednesday being the warmest as the ridge
axis passes overhead. The upper flow becomes westerly on Thursday as
the high breaks down ahead of another trough. Temperatures will
moderate by a few degrees in conjunction with an uptick in southwest
winds. The main concern here is the potential for critical fire
weather conditions to occur Thursday and Friday afternoons. Please
see the fire weather section below for more information.

As the aforementioned trough swings through the Great Basin and Four
Corners region Friday into this weekend, high temperatures may drop
to near seasonal averages. Though the GFS/ECMWF are coming into
better agreement with the evolution of this system, some differences
remain and the finer details will need to be ironed out in
subsequent forecast issuances. Regardless, this system looks to be a
dry one with precip remaining north of the area and zonal flow
keeping temperatures within a couple degrees of average through


.AVIATION...Valid thru 23/12Z.
Generally SKC conditions thru 22/16Z, then increasing high level
cirrus clouds above 20k ft AGL, with SCT-BKN clouds AOA 20k ft AGL
by 22/21Z. SFC wind less than 10 kts thru 22/18Z, then NWLY SFC wind
at most locales at 10-17 kts and gusts to around 20-25 kts. The
exception will be in the Gila River Valley near KSAD, with stronger
NWLY SFC wind at 20-25 kts and gusts to around 30 kts. SFC wind
diminishing areawide aft 23/02Z and generally less than 10 kts by
23/05Z. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...Dry conditions and above normal temperatures will
occur through Thursday, with daytime temperatures then lowering to
around normal late in the week. Expect an uptick in 20-ft winds much
of this week, with 20-foot winds in most eastern areas through
Wednesday reaching around 20 mph with higher gusts during the
afternoon hours. The exception will be in the upper Gila River
Valley around Safford where afternoon 20-foot winds will be between
20-25 mph with higher gusts at times through Wednesday and wind
speeds may briefly exceed critical fire weather thresholds. Stronger
southwest to west winds are then expected this Thursday and Friday.
Although to early for any kind of headline product, if current wind
forecasts hold true, much of the eastern half of the forecast area
will likely exceed critical fire weather thresholds Thursday and





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