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Area Forecast Discussion (AFD)

Issued by NWS Tucson Arizona (TWC)

FXUS65 KTWC 161043

Area Forecast Discussion
National Weather Service Tucson AZ
343 AM MST Mon Sep 16 2019

.SYNOPSIS...Scattered showers and thunderstorms this afternoon
into this evening. Less thunderstorm activity beginning Tuesday 
and prevailing into next weekend. The best coverage of showers and
thunderstorms should occur Thursday. Seasonably warm daytime 
temperatures this week.


.DISCUSSION...Clear across most of the area early this morning
with the area inbetween weather systems. Mainly high level cloud
cover was moving over western Pima county as of this writing out
in advance of a upper level trof that was off the PacNW. Adequate
moisture around today for isolated to scattered showers and
thunderstorms, a few that may briefly become severe, especially
west and north of Tucson later this afternoon into early this
evening. Although there will be isolated heavy rainers, flash
flooding on the low end due to fast movement of storms.

Drier air moving across the area on Tuesday as above mentioned
upper trof moves by to the north. Enough lingering moisture 
around for a slight chance of storms, mainly near the mountains, 
south and east of Tucson. 

Slight chance of afternoon storm mainly over eastern areas on 
Wednesday as southwest flow aloft starts to increase again as 
another Pacific trof enters the PacNW. As this trof moves inland
on Thursday it will pick up some moisture from the south for a
slight increase in storm chances east of Tucson. 

Drier westerly flow over the area Friday into the upcoming
weekend. Much uncertainty in the later part of the weekend into
early next week with respects to tropical moisture moving across
the area with GFS much wetter than ECMWF. At this time went with
slight chance of showers/storms on Monday.

High temperatures generally around normal during the next 7 days.


.AVIATION...Valid through 17/12Z.
SCT-BKN clouds above 15k ft AGL spreading across the area west to
east this morning. ISOLD-SCT TSRA/SHRA between 16/18z and 17/04z 
with clouds bases around 8k- 12k ft MSL. SFC winds remain less 
than 12 kts through the period, favoring a WLY-NWLY direction this
afternoon. Stronger gusts will be possible around TSRA. Aviation 
discussion not updated for TAF amendments.


.FIRE WEATHER...Expect showers and thunderstorms this afternoon 
and evening across much of southeast Arizona. A drying trend then 
occurs on Tuesday, which continues through the remainder of the 
week. However, isolated mountain storms will still be possible 
during the usual afternoon/evening timeframe. Light terrain driven
winds generally persist, except for breezier conditions on 
Thursday afternoon across western Pima County.





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