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Area Forecast Discussion (AFD)

Issued by NWS Tucson Arizona (TWC)

                            
000
FXUS65 KTWC 151737
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
1035 AM MST Sun Sep 15 2019

.SYNOPSIS...Scattered showers and thunderstorms this afternoon and 
evening east to south of Tucson with dry conditions elsewhere. 
Scattered showers and thunderstorms Monday into Monday evening 
across much of southeast Arizona. A drying trend will begin Tuesday 
with isolated thunderstorms east of Tucson Wednesday into Saturday.

&&

.DISCUSSION...A band of showers with occasional thunderstorms 
extended from southwestern Graham County southwestward into 
northwest Cochise County, and further southwestward into far eastern 
Pima County and eastern Santa Cruz County at this time. Other 
isolated showers producing light rainfall were occurring mainly near 
the New Mexico state line. Meanwhile, IR/visible satellite imagery 
and surface observations depicted clear skies across western Pima 
County, south central Pinal County, and much of the Tohono O'odham 
Nation.

The upper level cyclonic circulation system that moved into far 
southeast Arizona Saturday afternoon from Chihuahua Mexico had moved 
northward into east central Arizona at mid-morning. This system will 
continue to move northeastward toward the Four Corners region this 
evening while as a weakening upper shortwave trough.

Based on satellite/radar trends as well as the 15/12Z Univ of AZ 
WRF-NAM, 15/06Z Univ of AZ WRF-GFS, several HRRR solutions, and the 
15/12Z NAM12/GFS, modifications were made to the inherited PoPs/Wx
gridded data fields into tonight. In essence, PoPs were reduced to 
under 10 percent for much of the Tucson metro area while maintaining
single-digit PoPs west to northwest of Tucson. 

Meanwhile, maintained scattered to numerous coverage of showers and 
tstms this afternoon into early this evening east to south 
of Tucson. Isolated showers and thunderstorms should prevail late 
tonight mostly east of a Safford to Bisbee line, with perhaps 
scattered coverage across the White Mountains. The expectation of 
severe thunderstorms in this forecast area into tonight is nearly a 
zero percent chance.

High temps this afternoon are forecast to generally range about 
4-10 degrees below seasonal normals.

Please refer to the additional sections for further detail.

&&

.AVIATION...Valid through 16/18Z.
Scattered -TSRA/-SHRA this afternoon and evening east to south of 
KTUS, then isolated mainly -SHRA east of a KSAD-KDUG line late 
tonight into early Monday morning. Scattered -TSRA/-SHRA across much 
of southeast Arizona late Monday morning. Otherwise, cloud decks 
mainly 8k-12k ft MSL through valid period. Surface wind variable in 
direction mostly under 12 kts. Aviation discussion not updated for 
TAF amendments.

&&

.FIRE WEATHER...Scattered thunderstorms this afternoon and evening 
east to south of Tucson with dry conditions elsewhere. Scattered 
thunderstorms Monday across much of southeast Arizona. 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.

&&

.PREV DISCUSSION /232 AM MST/...Southwest flow aloft on Monday in 
advance of upper level trof moving thru the PacNW. Enough lingering 
moisture around for a chance of afternoon/evening storms across most 
of the area. 

Drying continues on Tuesday thus limiting chance of storms to
areas east of Tucson

Another Pacific trof enters the western CONUS on Wednesday. This
system may end up tapping into some tropical moisture from the
south. Something to monitor model trends but for now will keep 
only slight chance across the eastern mountains.

The remainder of the forecast generally dry across most of the
area except for the White mountains.

Highs temperatures below normal today and Monday then around
normal for the remainder of the week.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...none.

&&

$$

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