Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 270946

Area Forecast Discussion
National Weather Service Tucson AZ
245 AM MST TUE SEP 27 2016

.SYNOPSIS...A low pressure system over central Baja California will
move north into southern California tonight. This system will bring
scattered showers and thunderstorms mainly this afternoon and
evening. Moisture will remain sufficient for a chance of showers and
thunderstorms especially east of Tucson Wednesday and Thursday. Dry
conditions will return area wide late this weekend.


.DISCUSSION...Water vapor imagery this morning showed upper level
cut-off low over central Baja/Gulf of California. Radar showed
scattered showers/thunderstorms across northern Baja moving north
northwest while across SE Arizona there were spotty light showers.
As the cut-off low lifts to the north today, showers will be
increasing in coverage as the morning progresses, especially south
of Tucson. Latest HRRR runs along with 12z UofA WRF runs of NAM/GFS
all spread showers/storms near the intnl border north and northeast
across Pima/Santa Cruz. Some of these storms will briefly be strong
with outflow winds potentially bringing areas of blowing dust
between Tucson and Phoenix. Localized mod/hvy rainers with PW values
slightly over 1". However flash flooding threat low due to speed the
storms will be moving. With that said, made some significant upward
adjustments in PoPs and QPF for central/eastern Pima and Santa Cruz

Upper low continues north into southern California overnight with
gradual decrease in areal coverage of showers across the area.

Some moisture from TS Roslyn may spread toward the area on Wednesday
and Thursday keeping a chance of showers and storms across the area
as Monsoon 2016 comes to a close.

Drier SW flow aloft will push moisture to the east on Friday but
enough will be around to support a slight chance east of Tucson.

Dry westerly flow aloft this weekend into early next week as upper
level trofs pass by to the north.

Although warmer today versus Monday, highs will remain below normal
through Thursday then hang around normal values Friday into early
next week.


.AVIATION...Valid through 28/12Z.
Generally BKN-OVC clouds at 6-10k ft AGL thru the period, however
brief MVFR conditions and higher terrain obscurations may occur on
occasion. ELY/SELY sfc winds at 10-15 kts with a few gusts to near
20 kts are expected thru 28/03z...and aft 28/03z decreasing sfc wnd
to 8-12 kts thru the remainder of the forecast period. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...There will be a slight chance to chance of showers
and thunderstorms through Friday. East to southeast surface winds at
10-15 mph with some higher gusts will persist through Thursday.
Expect normal diurnal wind patterns to resume late this week into
the upcoming weekend. Dry and warmer weather is also expected over
this upcoming weekend.





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