Area Forecast Discussion
Issued by NWS Phoenix, AZ

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678
FXUS65 KPSR 262115
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
215 PM MST MON SEP 26 2016

.SYNOPSIS...
A developing low pressure system over northwest Mexico and the Baja
Peninsula will slowly move north toward southwest Arizona tonight.
Variable cloudiness, cooler temperatures, and a threat of showers
and afternoon thunderstorms are forecast. Partial clearing is
expected Wednesday, with a renewed chance of showers Thursday.
Dry and stable weather will return Friday through next Monday.

&&

.DISCUSSION...

Tonight through Tuesday Night...

The developing cutoff low pressure system over northwest Mexico/Baja
CA circulated a significant amount of moisture into southern AZ. Mid
and upper level moisture remains deeply saturated, resulting a
threat of sprinkles and or light showers over portions of southwest
and south central AZ tonight.

The Baja cutoff low pressure system is still forecast to slowly
migrate north toward Yuma by Tuesday evening, then into the Mohave
Desert just southwest of Las Vegas by Wednesday afternoon. As a
result, an unsettled weather pattern will continue though Tuesday
night with periods of clouds and a slight chance of showers and or
afternoon thunderstorms.


Wednesday...

We may get a little break in the weather in the subsidence southern
end of the passing low pressure system as it moves into the Mohave
Desert. However surface dewpoints will higher over the region for
humid day.


Thursday...

Another shortwave trof is forecast to move into southwest and south
central AZ from the southwest direction. The threat of showers and
thunderstorms are forecast over portions of southwest and south
central AZ Thursday afternoon and evening.


Friday through Monday...

A drier and more stable pattern is forecast this period under
increasing westerly flow aloft.


&&

.AVIATION...

South-Central Arizona Including KPHX, KIWA, and KSDL:

Stronger than normal easterly flow will continue across the Phoenix
terminals today with gusts likely reaching 25 to 30 kts this
afternoon before subsiding during the evening. Scattered to broken
mid to high level clouds aoa 10kft will persist through the period.
Showers and storms will not be likely over terminals; however, virga
or even sprinkles are a distinct possibility this afternoon.

Southeast California/Southwest Arizona including KIPL and KBLH:

Easterly winds gusting up to 15 to 20 kts will persist for the
remainder of the afternoon before winds subside this evening and
follow typical drainage headings. Skies will remain partly cloudy
with scattered to broken mid to high level clouds aoa 10kft.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Thursday through Monday...A low pressure system across the Desert
Southwest will bring an increase in moisture that will persist
through Thursday. The chance for showers and thunderstorms will be
highest across northeastern Arizona and across the higher terrain
north and east of Phoenix. However, some rain is possible in the
lower deserts, particularly Thursday. Drier conditions are
anticipated Friday and through early next week as southwesterly flow
develops ahead of an area of low pressure in the Pacific Northwest.
Winds will follow typical diurnal headings and remain on the lighter
side, with the exception of some afternoon breezes up to 15 to 20
mph in southwest Arizona and southeast California Saturday and
Sunday.

&&

.SPOTTER INFORMATION STATEMENT...
Skywarn radio Net activation will not be needed.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

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DISCUSSION...Vasquez
AVIATION...Hernandez
FIRE WEATHER...Hernandez



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