Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 010347
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
845 PM MST TUE MAY 31 2016

.SYNOPSIS...Expect isolated showers and thunderstorms this evening
and Wednesday mainly near the mountains. Otherwise, much hotter
daytime temperatures will prevail Thursday into early next week.
Highs will be around 110 degrees or hotter near and west of Tucson
this weekend.

&&

.DISCUSSION...No surprises tonight as the weak low we`ve been
discussing wobbles overhead tonight on it`s way immediately east and
southeast of the area tomorrow. Some light showers will linger
overnight, and there will be sufficient moisture for isolated valley
thunderstorms again tomorrow, with storms becoming more likely near
the mountains.

After that, the main story is still the heat from Thursday onward.
Temperatures will peak over the weekend for our part of the state,
with an Excessive Heat Watch currently in effect for Saturday and
Sunday.

Please see the previous discussion below for additional details.

&&

.AVIATION...VALID THRU 02/06Z.
Isolated to scattered -TSRA/-SHRA will occur mainly near the
mountains east of KTUS to the New Mexico border this evening and
again Wednesday afternoon. Brief wind gusts to around 35-40 kts may
occur. Otherwise, a few-sct clouds around 10-15k ft msl and sct-bkn
clouds above 20k ft msl will prevail through the period. Surface wind
early this evening and Wednesday afternoon will be swly/wly at 10-20
kts with gusts to near 25 kts. Surface wind will be less than 10 kts
at other times. Aviation discussion not updated for TAF ammendments.

&&

.FIRE WEATHER...Isolated to scattered showers and thunderstorms are
forecast to occur this evening and Wednesday mainly near the
mountains across Greenlee, Graham and Cochise Counties east of
Tucson. A slight chance of showers and thunderstorms continues
Thursday mainly near the New Mexico border. Expect gusty and
erratic winds near these showers and thunderstorms. Thereafter, dry
conditions with very hot daytime temperatures and generally light
winds will prevail Friday into early next week.

&&

.PREV DISCUSSION...A weak upper low pressure system over northwest
Sonora Mexico will move eastward into northwest Chihuahua Mexico
midday Wednesday. Various NWP models suggest that the best chance
for showers/tstms Wed afternoon/evening will be across eastern
sections. Thus, have continued with isolated to scattered
showers/tstms Wed afternoon/evening mainly near the mountains of
Greenlee/Graham/ Cochise Counties. Expect dry conditions area-wide
late Wed night/ Thur morning followed by a slight chance of
showers/tstms across the White Mountains Thursday afternoon.

The official forecast then depicts dry conditions starting Thursday
evening and continuing into early next week as strong high pressure
aloft prevails over the swrn CONUS. The 31/12Z GFS/ECMWF were
similar by midday Sunday with depicting a weak upper low to be
centered near the central California coast. This upper low is then
progged to fill over the Great Basin by next Tuesday. However, the
ECMWF was considerably more robust versus the GFS with depicting
fairly ample moisture mainly across eastern sections by next Tue.
For now, have opted for a drier scenario with this forecast issuance.

High temps Wednesday should be a few degs warmer versus temps
achieved this afternoon followed by about 5 degs or such of daily
warming Thursday thru Saturday. Expect no significant change in
daytime temps Sunday. Opted to issue an Excessive Heat Watch for
Saturday and Sunday with forecast high temps mainly in the 108-113
degree range from Tucson westward into the western deserts. Portions
of the Upper Gila River Valley including Safford also meets criteria
for this Watch. A slight moderation in daytime temps is should then
occur Monday into Tuesday, but high temps will still remain well
above normal.

&&

.TWC Watches/Warnings/Advisories...
    Excessive Heat Watch from Saturday afternoon through Sunday
      evening for AZZ501>507-509.

&&

$$

Meyer/Francis

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