Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 261009
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
309 AM MST Thu Apr 26 2018

.SYNOPSIS...
Very warm and dry conditions will continue into the first part of
the weekend as lower desert high temperatures reach into the
middle to upper 90s each day. A slight chance for showers will
exist across southern Gila County Friday and Saturday afternoon as
a weak storm system moves across the area. A cooling trend
starting Sunday will eventually lead to below normal temperatures
starting early next week.

&&

.DISCUSSION...
A deep Pacific low off the West Coast will help to build heights a
bit further over the region today leading to highs to around 100
degrees for the warmest desert locations. Further east a cold
front will dive southward through the western Plains states and
the central Rockies. Eventually this cold front will push westward
through New Mexico early tonight and then into far eastern
Arizona by early Friday morning. This cold front will bring a
short period of modestly strong southeasterly low level winds into
eastern Arizona. Low and mid level moisture levels will also increase
behind the front allowing for enough moisture for isolated
showers and maybe a few thunderstorms across the eastern Arizona
high terrain starting Friday afternoon. A southwesterly steering
flow will keep any rain activity over the high terrain, but we
can`t completely rule out the possibility of outflow winds
traveling westward far enough to reach the foothills or lower
deserts in Pinal and eastern Maricopa Counties.

Temperatures Friday will drop a couple degrees from today`s highs
as heights aloft lower from the approaching Pacific trough that
begins to move onshore across northern California and Oregon. This
trough will be slow to progress eastward this weekend as the low
center only reaches Idaho by Sunday night. Shower and thunderstorm
chances will again return across eastern Gila County for the
daytime hours Saturday with better upper level support as the
trough nears the region. Rain chances will however come to an end
Saturday evening as westerly flow increases pushing much drier
air through the region. The trough will remain mostly to the north
of our area this weekend as it slowly drifts eastward, but it
will bring increased breeziness and a cooling trend. Highs
Saturday will still be several degrees above normals, but Sunday`s
readings should drop into the upper 80s to around 90 over the
deserts, or right around normals.

The trough will open up and become more expansive next Monday into
Tuesday while a shortwave trough digs southward down the backside
of the trough. Though there is still some model spread, models
mostly agree another closed low will develop from this diving
shortwave trough. This could result in a closed low moving through
the Desert Southwest sometime during the middle of next week,
most likely on Wednesday. This scenario would bring at least a
slight chance of showers and thunderstorms to the high terrain,
possibly even some high based storms over the deserts in an ideal
situation where moisture levels are high enough and the low
center passes through southern Arizona. Temperatures for next week
should take a decent hit with highs easily falling into the
middle 80s, possibly lower 80s in some lower desert spots.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:

High pressure aloft and weak gradients will result in winds
following typical diurnal tendencies for the next 24 hours at speeds
mostly below 10kt. There will be some high clouds at times with FEW-
SCT decks above 20k feet and by Thursday morning expect some CIGs as
well but much of the BKN decks will be on the thin side. No aviation
concerns at any of the terminals for the next 24 hours.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation weather concerns are anticipated through Thursday
evening. Light diurnal winds with mostly clear skies are
anticipated. Winds to favor the west at KIPL and the south to
southwest at KBLH.

Aviation Discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Saturday through Wednesday... Very warm
temperatures will exist on Saturday before cooling slightly by
Sunday. A weak weather disturbance and modest moisture increase will
bring a slight chance for thunderstorms, primarily for Gila County,
on Saturday afternoon. Any rainfall amounts will be minimal and
conditions favorable for dry lightning will exist. Otherwise, some
afternoon breezes are possible each day, with the strongest gusts on
Monday and Tuesday afternoons.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters are encouraged to follow standard reporting procedures.

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...CB
FIRE WEATHER...Rogers


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