Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 251005

Area Forecast Discussion
National Weather Service Tucson AZ
305 AM MST SUN SEP 25 2016

.SYNOPSIS...A low pressure system south of the area will bring
scattered showers and isolated thunderstorms tonight into Tuesday.
Gusty east winds will also accompany this system. A chance of
showers and thunderstorms continues Wednesday and Thursday mainly
east of Tucson, then a drying trend will occur by next weekend.


.DISCUSSION...Water vapor imagery this morning showed a developing
upper level low just east of Douglas. This feature will be the main
driver of our weather for the next four to five days. As this upper
low continues to sag southwest across Sonora Mexico, the flow aloft
will become easterly. Back door cold front will push low-mid level
moisture back across the area today. Best chances for showers and a
few t-storms will be along the international border as far west as
San Miguel. Mid-level gradient peaks later tonight into Monday
morning with strong gusty east winds in favored areas from Tucson
south and east. MOS guidance would suggest that some areas might
meet wind advisory criteria. Something for later shifts to ponder.
Chance of light showers/slight chance of thunder will push west
northwest tonight into Monday morning.

The threat of showers and t-storms will continue Monday night into
Wednesday as the above mentioned upper low, after bottoming out near
the Baja Spur, lifts north into western Arizona. The 25/00z runs of
the UofA WRF NAM and GFS suggest that afternoon thunderstorms on
Tuesday may get rather frisky west of Tucson.

The later part of this week will see some drier air push in with
chance of showers mostly east of Tucson on Thursday and Friday.

Below normal high temperatures will be around through Wednesday


.AVIATION...Valid through 26/12Z.
An upper level low developing near Douglas this morning will sag
south into Sonora Mexico today. This feature will bring an
increasing moist easterly flow across the area with strong gusty
east winds developing after 26/00z in areas susceptible to easterly
gradient scenario. Thus sfc wind light and terrain driven this am
bcmg E-SE 8-12 kts this aftn, increasing 10-20 kts this evening with
locally higher gusts up to 25 kts after 26/06z, especially at KTUS.

SCT clouds at 8-12k ft AGL mainly S and E of KTUS this am will
gradually spread W into this aftn. Cloud decks becoming BKN late
this aftn into this evening. Isold -SHRA/Slight chc TS along/near
the International border later this aftn spreading W/NW after
26/00z. Aviation discussion not updated for TAF amendments.


.FIRE WEATHER...An upper level low over northwest Mexico will
spread moisture from east to west across the area starting today and
continue through Wednesday. This will bring a chance of showers and
possibly a few thunderstorms this evening through Wednesday.
Variable and terrain driven surface wind less than 10 mph this
morning becoming easterly around 15-20 mph this afternoon and
persisting into Tuesday.





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