Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 06/13/19

Area Forecast Discussion

National Weather Service Phoenix AZ

 431 PM MST Wed Jun 12 2019

.UPDATE...Updated Aviation discussion.

&&

.SYNOPSIS...
Excessive heat conditions will remain an issue through Thursday
with afternoon high temperatures at or just over 110 degrees for
the lower deserts. A low pressure system approaching from the
northwest will slowly move through the region Friday and Saturday
bringing some relief with cooler temperatures by Friday, but very
dry conditions will continue to prevail. Near to slightly below
normal temperatures are then anticipated this weekend into next
week.

&&

.DISCUSSION...
Strong high pressure (current 500 mb heights are above the 90th
percentile) will lead to well above average temperatures across
our entire forecast area today. There`s a narrow band of upper-
level moisture across south-central Arizona, resulting in a decent
amount of cirrus clouds this afternoon. This band of cirrus
clouds will continue to get swept out to the east with mostly
clear skies expected by late this afternoon. Despite the cloud
cover, temperatures will still climb into the 110 to 115 degree
range and due to this an Excessive Heat Warning continues for
nearly our entire CWA today and the proper actions should be taken
to lessen the impact of extreme heat.

Aforementioned high pressure will weaken as a weak shortwave
trough moves into the western CONUS late tonight through tomorrow.
Heights will fall ahead of this wave resulting in slightly cooler
temperatures tomorrow across the southwestern portion of our
forecast area. Due to this, the Excessive Heat Warning will only
continue for the lower deserts of south-central Arizona, all of La
Paz county, and along the Colorado River Valley tomorrow where
high temperatures between 110 and 113 degrees are forecast and
where there is a moderate to high HeatRisk. A tightened pressure
gradient will also exist tomorrow and result in breezy afternoon
conditions with gusts up to 20-30 mph. Minimum humidities will be
in the single digits as well tomorrow afternoon, thus elevated
fire danger conditions will exist (more information in our Fire
Weather Forecast).

Friday to Sunday, the main trough will move into and across our
forecast area. This will bring a big cool down to the entire
region, with highs near or just below average this weekend. With
the presence of the trough, expect some afternoon breeziness
Friday and this weekend, with gusts up to 15-20 mph.

By early next week, another weak trough moves into the western
CONUS, with this pattern remaining in place through the middle
part of the week. This will keep temperatures at or below normal
Monday through Wednesday with sunny skies and some afternoon
breeziness mainly in the teens.

&&

.AVIATION...Updated at 2330 UTC.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

For the rest of tonight, the winds will remain westerly at 5-10
kts before becoming easterly. The easterly switch will happen
around 10Z for KPHX but earlier at the other terminals. Smoke/haze
from nearby forest fires may create some slantwise visibility
issues for aircraft on eastward approaches/takeoffs during the
evening and early morning hours.Tomorrow, an approaching
disturbance will create strong westerly winds by the early
afternoon with gusts 15-25 kts and lasting well into the evening.


Southeast California/Southwest Arizona including KIPL and KBLH:

Winds to increase and become breezy from the southwest to west.
Gusts over 20kt possible after about 23z into the mid evening
before tapering off, before even stronger winds develop on Thu
afternoon. FEW cirrus decks becoming CLR by late afternoon/early
evening.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Saturday through Wednesday:
Several weak low pressure systems will sweep through the region
this weekend and early next week bringing temperatures back to
near seasonal average. However, very dry conditions will also
prevail with afternoon humidity values generally falling to around
10-15% following only poor to fair overnight recovery. Very
typical afternoon upslope breeziness (gusts mainly in the teens)
should settle into the region during the weekend and persist into
early next week with afternoon winds favoring the south to
southwest.

&&

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Thursday for AZZ530-533-
     534-537>544-546-548>556-559.

     Excessive Heat Warning until 8 PM MST this evening for AZZ531-
     532-536.

CA...Excessive Heat Warning until 8 PM PDT Thursday for CAZ569-570.

     Excessive Heat Warning until 8 PM PDT this evening for
     CAZ561>568.

&&

$$

DISCUSSION...Hernandez
AVIATION..Deemer/Percha
FIRE WEATHER...Hernandez