Red Flag Warning 2, NWS Tucson, AZ

Area Forecast Discussion
National Weather Service Tucson AZ
240 PM MST Mon Apr 20 2020

.SYNOPSIS...Dry conditions along with a significant warming trend
can be expected this week. Gusty afternoon winds will also occur,
especially on Tuesday as a weather system passes through the region.
High temperatures approaching the upper 90s to around 100 degrees
will be possible in the lower deserts this coming weekend.

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.DISCUSSION...Cirrus clouds are streaming in from the southwest out
ahead of a trough currently situated over the west coast. As the
larger scale trough moves east a series of shortwaves will move
through Arizona starting tonight into Wednesday. This will lead to
strong and gusty winds Tuesday afternoon for much of the area.
Because of these winds along with low relative humidity and high
fire danger the fire weather watch for areas east of Tucson Tuesday
afternoon has been continued. However, the watch area was trimmed
back further east to no longer include eastern Pima, Pinal, and
Santa Cruz counties. New model data suggested wind speeds would
not reach critical fire weather thresholds in those areas. See the
fire weather section for more details.

Wednesday the last shortwave will be exiting Arizona and winds will
still be elevated but no impacts are expected. Also, some areas in
far western Pima County could see 90 degrees. By Thursday ridging
will be in place leading to high temps in the low 90's in the Tucson
metro area for the first time this year. Ensemble guidance shows
the ridge staying in place into early next week and building over
the weekend. This will result in temperatures warming into early
next week with high temperatures in the upper 90's and even 100
degrees in far western Pima County.

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.AVIATION...Valid through 21/12Z.
FEW-SCT clouds AOA 25k ft MSL expected through early this evening
becoming SKC-FEW AOA 25k ft MSL overnight. SKC expected Tuesday for
all terminals. Light and variable sfc winds expected overnight
increasing generally from the west Tuesday late morning into the
afternoon. Expect sfc winds between 12-17 kts, gusting to to 20-25
kts for KTUS/KOLS and 17-22 kts, gusting to 30-35 kts for KDUG.
Aviation discussion not updated for TAF amendments.

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.FIRE WEATHER...Expect dry conditions the next 7 days with min RH
values between 8-17% in the valleys. By this weekend, min RH values
could drop as low as 5-7%. For the mountains, expect min RH values
in the 15-25% range. Overnight RH recoveries will be fair to good
through Wednesday morning, then drying out with fair to Poor
recoveries expected each morning into the weekend.

High temperatures will generally be within a couple of degrees of
normal through Wednesday, then warm into the mid 80s to lower 90s in
the valleys late in the week. Some valley locations will rise into
the middle and upper 90s by the weekend.

Breezy conditions are expected Tuesday, which will result in at
least localized critical fire weather thresholds being met or
exceeded in locations to the east/southeast of Tucson Tuesday
afternoon into early Tuesday evening. Recent model guidance is now
suggesting the winds will be lighter. Due to the new guidance,
decided to continue the Fire Weather Watch for eastern sections of
Fire Weather Zone 151 and much of Fire Weather zone 152. In fact,
the watch was pulled out of the eastern sections of Pima, Santa
Cruz, and Pinal Counties. Additional adjustments to the coverage or
even a cancellation may be needed if these trends continue. Elsewhere
across southeastern AZ, fire weather will be elevated.

Elevated winds are then expected to continue across the eastern half
of the forecast area Wednesday through Friday. At this time, wind
speeds are expected to remain below critical fire weather
thresholds.

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.TWC WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Tuesday afternoon through Tuesday
evening for AZZ151-152.

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