fxus65 ktwc 210420 

Area forecast discussion 
National Weather Service Tucson Arizona 
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...infrared 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 above ground level 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 


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 


Previous 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. 



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