Area Forecast Discussion
Issued by NWS Tucson, AZ

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210
FXUS65 KTWC 240944
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
244 AM MST Sat Jun 24 2017

.SYNOPSIS...Very hot temperatures will continue this weekend.
We`ll also see increasing thunderstorm chances with the most
action on Sunday and Monday. Some drying will limit thunderstorms
the second half of the new week, with temperatures closer to
normal for late June as we back away from the record heat.

&&

.DISCUSSION...Plenty of debris cloud again this morning left over
from earlier convection near and south of the border. Moisture
trends are down over the past 24 hours, with surface dew points
down 8 to 12 degrees (upper 30s to mid 40s), and precipitable
water values between 1/2 and 3/4 of an inch as per sounding
measurements and satellite estimates. That trend is in the process
of doing another 180 as mid level moisture from the south and
east is wrapping back into the area around the high, and pushing
precipitable water values back near and then above 1 inch over the
next 24 hours.

That high is reconsolidating immediately overhead, so another day
of near record high temperatures with an Excessive Heat Warning
still in place. Convection chances will be highest around the
eastern and southern periphery of the high, so that would be our
far eastern and southern areas this afternoon. By tomorrow
moisture will have pushed far enough back into the area for
better thunderstorm coverage Sunday and Monday.

The ridge will weaken fairly quickly starting Monday as a dry
zonal flow sets up under a more active higher latitude pattern,
and the record height and thickness values we`ve been seeing over
the past week recede closer to normal levels. As this happens,
temperatures will do the same, and our chance of thunderstorms
will diminish considerably by Wednesday or Thursday.

Another tropical cyclone forming near the southern Mexican coast.
This one will likely take a more northwesterly track with both the
GFS and ECMWF taking the remains just southwest of the tip of Baja
around Tuesday or Wednesday next week. No direct impacts for us,
but it will probably help prime western Mexico with deeper
moisture. It could even contribute to moderate surge activity the
second half of next week.

&&

.AVIATION...Valid thru 25/12Z.
FEW-SCT clouds at 8k-15k ft AGL thru the forecast period, with
ISOL`D-SCT SHRA/TSRA E/SE of KTUS this afternoon and evening. SFC
wind variable in direction and less than 10 kts through this
morning. This afternoon, expect WLY/NWLY wind at 10-14 kts with
gusts to 20 kts. SHRA/TSRA may produce wind gusts to 40 kts.
Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Scattered thunderstorms generally from Tucson
eastward and southward through Tuesday. Expect decreasing coverage
of thunderstorms Wednesday, with isolated to scattered thunderstorms
mainly east to south of Tucson. Dry conditions are forecast to
prevail across much of the area next Thursday and Friday.

Morning southeasterly winds and afternoon northwesterly winds will
be periodically gusty through the Gila River Valley this weekend.
Additionally, any convection which develops will be capable of
producing gusty erratic wind gusts in excess of 40 mph. Otherwise,
20-foot winds will then exhibit diurnal trends with speeds mainly
less than 15 mph, although some elevated afternoon gusts may occur
due to strong daytime heating.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 7 PM MST Sunday for AZZ501>507-509-
515.

Heat Advisory until 7 PM MST this evening for AZZ511-513.

Heat Advisory until 7 PM MST Sunday for AZZ514.

Excessive Heat Warning until 7 PM MST this evening for AZZ508.

&&

$$

Meyer/French

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