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Area Forecast Discussion (AFD)

Issued by NWS Tucson Arizona (TWC)

FXUS65 KTWC 142230

Area Forecast Discussion
National Weather Service Tucson AZ
330 PM MST Sat Sep 14 2019

.SYNOPSIS...Adequate moisture for scattered showers and 
thunderstorms through Monday. Some thunderstorms this evening may 
produce damaging winds and blowing dust northwest of Tucson. A 
drying trend will begin Tuesday with isolated thunderstorms east of 
Tucson Wednesday into next Saturday.


.DISCUSSION...Scattered showers producing light rain amounts were 
continuing this afternoon across central/northern Cochise County 
northward into southern Graham/northern Greenlee Counties. 
Meanwhile, strong thunderstorms were occurring just north of this 
forecast area, or across portions of south central Arizona. The area 
of showers and thunderstorms was ahead of a northward moving 
cyclonic circulation system that has moved into far southeast 

Based on radar trends, the area of showers east of Tucson should 
gradually decrease into early this evening. Meanwhile, stronger 
thunderstorms should continue to develop north of this forecast area 
with thunderstorms moving toward the west and southwest into this 
evening. Although the bulk of these thunderstorms should remain 
northwest to north of the area, the potential exists for strong to 
perhaps severe thunderstorms especially across southern Pinal 

A Severe Thunderstorm Watch is in effect until 10 PM MST for 
southern Pinal County. A Blowing Dust Advisory is also in effect 
until 8 pm MST this evening. The Blowing Dust Advisory includes 
western Pima County; much of the Tohono O'odham Nation; the western 
portion of south central Pinal County; and a small portion of 
eastern Pima County northwest of Tucson. Expect the stronger 
thunderstorms to decrease in coverage and intensity by midnight.

Various models depict the northward moving cyclonic circulation 
system will move northward toward the White Mountains by daybreak 
Sunday. As such, showers with embedded thunderstorms may develop 
late tonight into early Sunday morning further west and southwest of 
this feature, including the Tucson metro area. As the weakening 
upper low drifts northward into northeast Arizona Sunday afternoon, 
scattered showers and thunderstorms are forecast to occur mainly 
from Tucson eastward to the New Mexico state line.

The flow aloft on Monday remains progged to become increasingly 
southwesterly ahead of a deepening upper trough over the Pacific 
Northwest and Great Basin. Moisture is also progged to remain 
adequate to justify scattered showers and thunderstorms Monday 
afternoon and evening especially from Tucson eastward. A drying 
trend should begin Tuesday under westerly flow aloft. As such, 
expect isolated to scattered showers and thunderstorms Tuesday 
afternoon and evening from Tucson eastward.

Markedly less coverage of showers and thunderstorms will likely 
prevail Wednesday as the bulk of deeper moisture is progged to be 
shunted well east of this forecast area. Isolated to perhaps 
scattered showers and thunderstorms Thursday into next Saturday 
should be limited to mountains east of Tucson, and especially favor 
the White Mountains, in response to a southwest flow aloft regime.

Forecast high temps Sunday and Monday will generally be a few 
degrees below seasonal normals. A gradual warming trend will then 
prevail Tuesday into Thursday with daytime temps trending a couple 
of degrees or so above normal Friday and Saturday.


.AVIATION...Valid through 16/00Z.
Scattered -TSRA/-SHRA this evening favoring locales west to north of 
KTUS. Brief wind gusts to 45 kts reducing VSBYS to under 1SM in BLDU 
this evening with stronger TSRA. Isolated -SHRA east of KTUS 
decreasing in coverage this evening, then isolated to scattered 
-TSRA/-SHRA mainly from KTUS vicinity eastward late tonight into 
Sunday afternoon. Otherwise, cloud decks mainly 8k-12k ft MSL.
Surface wind mainly nely to sely 8-18 kts with gusts near 30 kts 
this evening, then surface wind variable in direction mostly under 
12 kts late tonight into Sunday afternoon. Aviation discussion not 
updated for TAF amendments.


.FIRE WEATHER...Expect scattered thunderstorms through Monday. 
Isolated to scattered thunderstorms Tuesday mainly from Tucson 
eastward, then isolated thunderstorms Wednesday into next Saturday 
east of Tucson. Aside from thunderstorm wind gusts, 20-foot winds 
will be terrain driven mostly under 15 mph.


  Blowing Dust Advisory until 8 PM MST this evening for AZZ501-502-



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