Area Forecast Discussion
Issued by NWS Tucson, AZ

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463
FXUS65 KTWC 210420
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
920 PM MST Fri Oct 20 2017

.SYNOPSIS...A passing system will bring cooler temperatures Saturday
and Saturday night. After another possibly cooler night Sunday, well
above normal temperatures will return by Monday as strong high
pressure builds over the area. Expect record or near record daytime
temperatures Monday into Wednesday.

&&

.DISCUSSION...IR satellite imagery depicted clear skies generally
across northern sections of this forecast area to mostly clear skies
from Tucson vicinity southward at this time. The 21/00Z KTWC
sounding depicted moderate to fast wly/nwly flow above 500 mb, and
this regime was in response to a low amplitude upper trough over the
Intermountain West. Gusty southwest to west winds that occurred this
afternoon had diminished to mainly less than 15 mph at most locales
as of 9 pm MST.

Expect clear skies or a few to scattered thin cirriform clouds
moving across the area the rest of tonight. Low temperatures around
daybreak Saturday will be about 5-10 degrees cooler versus temps
achieved early this morning.

The official forecast has an excellent handle on this scenario and
no updates are necessary at this time. Please refer to the
additional sections for further detail.

&&

.AVIATION...Valid thru 22/06Z.
Clear skies to scattered clouds above 20k ft AGL into Saturday
evening. Surface wind Saturday afternoon nwly 8-18 kts. Gusts to
near 25 kts will be most likely northeast of KTUS and especially in
vicinity of KSAD. Surface wind variable in direction mainly less
than 12 kts at other times. Aviation discussion not updated for TAF
amendments.

&&

.FIRE WEATHER...Dry conditions to continue into next Friday. Gusty
northwest winds will occur Saturday afternoon east of Tucson and
especially across the Upper Gila River Valley including Safford.
Expect gusty east winds at times Sunday into Wednesday.

&&

.CLIMATE...90 degree days at Tucson International Airport continue
to mount, with the 180th day of 90+ degree high temperatures
today. We continue to put distance between 2017 and the old record
of 178 days which occurred in 1910 and 1989. After a break
Saturday, more to come next week.

Record or near record high temperatures are likely early next week
as an unseasonably strong ridge of high pressure aloft builds over
the area. The current forecast high of 97 for Tucson International
Airport on Tuesday would be the second latest occurrence of 97 on
record. The record latest date is Oct 27 2016. There is also a small
chance on Tuesday that the high at Tucson International Airport
could hit 98; which, if that happens, would be the latest occurrence
of 98 in the calendar on record, besting the current latest date of
October 19 in 1921 and 1991.

         Tucson International Airport
             Forecast  Record
Mon Oct 23      96       94
Tue Oct 24      97       96
Wed Oct 25      94       95

&&

.PREV DISCUSSION /252 PM MST/...The trough passing through the
region is deep enough to bring breezy conditions to our area this
afternoon, but not much else as precip and the main storm track
remain well north of our area.

Cooler air behind the frontal passage Saturday, with temperatures
actually dropping back to near or below average Saturday afternoon
and Saturday night. Much cooler morning lows Sunday, with middle 30s
to middle 40s in coldest eastern valleys to upper 40s and 50s from
Tucson westward. Lower dew points Sunday night into Monday morning
may facilitate even cooler temperatures in colder eastern Valleys,
with a few locations near freezing possible in Sulphur Springs
Valley and other cold prone locations. We`re currently expecting dew
points to drop into the 20s and upper teens. If they crater into the
lower teens and single digits we may actually end up needing a
freeze warning for portions of Cochise County.

A world beater ridge building in from the eastern Pacific will push
our temperatures to record levels the first half of next week,
including middle to upper 90s for Tucson International Airport.
Please see the Climate section for additional details.

&&

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

&&

$$

Francis
PREVIOUS DISCUSSION...Meyer

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