Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 192221

Area Forecast Discussion
National Weather Service Tucson AZ
321 PM MST Thu Oct 19 2017

.SYNOPSIS...A fast moving disturbance will bring isolated showers
and thunderstorms east of Tucson this afternoon and early
evening. A stronger passing system will bring breezy conditions
Friday and cooler temperatures Saturday and Saturday night.
Another ridge of high pressure will push temperatures rapidly back
up, with near record high temperatures expected the first half of
next week.


.DISCUSSION...The weak mid level impulse pushing across the area
into the back side of the ridge is now exiting into western New
Mexico this afternoon. Isolated showers and very isolated
thunderstorms are now well east of Tucson and should be out of the
picture entirely early this evening. Modest moisture.

A strong system currently pushing into the Pacific Northwest from
the Gulf of Alaska will dampen a bit as it moves through the
central and northern Great Basin. However, it will pass through
the region close enough to us to generate breezy southwest to west
winds Friday, followed by a frontal passage Saturday that will
push temperatures back to near or even a little below average for
a day.

Cooler overnight lows will also result, with Saturday night and
Sunday night into Monday morning the coolest nights. With the
frontal passage timing still not easy to pin down Saturday
(probably mid morning through late afternoon as it fragments
through our area), conditions may still be a little unsettled
Saturday evening. The drier air and lighter winds might be most
evident Sunday night into Monday morning, with overnight lows
falling below average. That means a few of the coldest valley
spots in Cochise County (such as Sulphur Springs Valley) may
flirt with freezing.

A more amplified pattern will then bring a strong ridge from the
eastern Pacific building into California and Arizona early next
week. Forecast height and thickness values support near record
temperatures around 12 to 14 degrees above average Monday through
Wednesday. Please see the Climate section below for additional


.AVIATION...Valid thru 21/00Z. SCT-BKN clouds at 9-12k ft AGL,
partial clearing from the west this evening. Isold -SHRA east of
KTUS until 20/03Z. Normal diurnal wind trends overnight less than
10 kts, increasing from the west Friday afternoon. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...A weak disturbance moving across the region will
result in isolated showers and thunderstorms over far eastern
areas through this evening. Dry conditions are then expected
starting on Friday and continuing through at least the middle of
next week. Southwest winds will be up just a bit today and then
winds will be breezy from the southwest to west on Friday into
Saturday. An easterly wind regime sets up on Sunday into early
next week.


.CLIMATE...Record setting for Tucson with today being the 179th
day of 90+ degree high temperatures for 2017. This breaks the
record of 178 days which occurred in 1910 and 1989.

After a break over the weekend, record or near record high
temperatures are likely early next week as an unseasonably strong
ridge of high pressure aloft builds over the area. Current forecast
high of 97 for Tucson Intl next Tuesday would be the 2nd latest
occurrence of 97 in the calendar on record. The record latest date
is Oct 27 2016. There is also a small chance next Tuesday that
the high at Tucson Intl 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 Oct 19 in 1921 & 1991.

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






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