FXUS65 KTWC 231004

Area Forecast Discussion
National Weather Service Tucson AZ
304 AM MST Fri Jun 23 2017

.SYNOPSIS...Very hot temperatures will continue into this weekend.
A little drier today before a more favorable pattern provides
increasing thunderstorm chances, with scattered afternoon and
evening thunderstorms Sunday into the middle of next week.


.DISCUSSION...We`re still seeing some debris cloud this morning
from the convection yesterday and last night near the border.
Trends will be down a little more today with weak drying in a
temporary northwesterly flow.

The ridge over the desert southwest is weakening, but still very
potent as we see one more solid reconsolidation overhead Saturday.
A weaker flow will also see increasing mid level moisture slip
back into the area with as evidenced by a strengthening 700hPa
theta-e ridge through Sonora and Southeast Arizona by Sunday.

Not as hot to start the new week with weakening high pressure and
the increasing moisture. Some solid thunderstorm days Monday-
Wednesday, but the deeper moisture will still not be in position
to provide the more prevalent heavy rainfall / wet micro- burst
style storms. Another batch of early season storms that generate
impressive outflows and dry lightning with limited significant
rainfall amounts.

The ridge will weaken and drop into a blocking position with a
more active higher latitude pattern the second half of the new
week. That will depress the most significant thunderstorm activity
back into Mexico for a few days.


.AVIATION...Valid thru 24/12Z.
Periods of SKC and FEW-SCT clouds at 10k-15k ft AGL thru the
forecast period. SFC wind variable in direction and less than 10 kts
through this morning, except for NWLY winds around 12 kts near KSAD.
This afternoon, expect NWLY wind at 10-15 kts with gusts to 25 kts,
with strongest wind speeds in the vicinity of KSAD. Aviation
discussion not updated for TAF amendments.


.FIRE WEATHER...Dry conditions will prevail across much of the
area through Saturday. The exception will be in the higher terrain
along the New Mexico border and in the White Mountains where there
is a slight chance of showers and thunderstorms. A more favorable
pattern for thunderstorms will then prevail Sunday through next
Wednesday. Expect scattered afternoon and evening thunderstorms,
especially from Tucson south and eastward. However, the coverage of
thunderstorms Monday into Tuesday will also include the eastern
portion of Fire Zone 150.

20-foot winds will generally be terrain driven and less than 15 mph.
The exception will be elevated northwest winds through the Gila
River Valley near Safford into this afternoon, with speeds of around
20 mph and gusts to 30 mph. Additionally, any convection which
develops this weekend and next week will be capable of producing
gusty and erratic winds.


Heat Advisory until 7 PM MST Sunday for AZZ510>514.

Excessive Heat Warning until 7 PM MST Sunday for AZZ501>509-515.




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NWS TWC Office Area Forecast Discussion