000
FXUS65 KPSR 271719
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1019 AM MST Thu Feb 27 2020

.UPDATE...Updated Aviation discussion.

&&

.SYNOPSIS...
High pressure building into the region over the next couple days
will lead to warmer conditions and high temperatures climbing to
above the 80 degree mark across the lower deserts for Friday and
Saturday. A storm system early next week will bring cooler
temperatures and chance for precipitation. The best chances will
be Monday over the higher terrain areas of eastern Arizona.
Warmer conditions are expected to return by the middle of next
week.

&&

.DISCUSSION...
Clear skies remain over the region as an upper level ridge
continues to slowly build in from the southwest. Considerable
warming aloft will take place through Friday with high
temperatures today warming about 10 degrees over yesterday`s
readings. Thursday night into Friday a weakening southern stream
Pacific trough centered well west of southern California will
begin pulling some high level subtropical moisture northeastward
into our region. This will lead to a period of high level
cloudiness through around mid day Friday, but this should not stop
daytime highs Friday from reaching from around 80 degrees in the
Phoenix area to close to 85 degrees across the southeast
California deserts.

By Saturday, the weakening trough will be barely noticeable as it
ejects northeastward through our region while temperatures stay
similar to Friday`s readings. Also on Saturday, an upstream
Pacific shortwave trough is shown diving southward just off the
Pacific Northwest coast before it deepens as it comes ashore in
northern California. Models continue to be fairly consistent with
the evolution of this positively tilted trough as it enters our
region later on Sunday with further deepening as the center of
the low moves into southern California Sunday night. Strong height
falls aloft and an increasing pressure gradient over our region
ahead of the low should lead to breezy to windy conditions by
Sunday afternoon, especially across southeast California and
southwest Arizona. As the trough begins to enter the region
Sunday, high temperatures are forecast to drop back to near normal
readings.

Fairly strong agreement is already seen among the majority of the
model ensemble members and operational runs showing the deep
positively tilted closed low tracking through southern California
and eventually near the Arizona/Mexico border on Monday. This
solution does not allow for strong moisture advection into the
region, but there should still be enough available system moisture
to bring good rain and snow chances to the eastern Arizona high
terrain on Monday. At this point, rain chances over the lower
deserts look to be somewhat limited, but this could still change
if the system deepens further allowing it to slow down and
potentially tap into deeper moisture over northern Mexico. The
system does look to be on the colder side and this should lead to
a significant drop in snow levels on Monday and rain changing to
snow for locations mostly above 4500-5000 feet in eastern Arizona.
Due to the expected light QPF amounts, snows across the higher
terrain should be relatively minor. High temperatures Monday
should be fairly chilly with readings in the low to mid 60s
across the lower deserts, but improving back to around normal
readings by next Tuesday or Wednesday after the trough exits well
to the east.

&&

.AVIATION...Updated at 1818Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Southeast California/Southwest Arizona including KIPL and KBLH:

Mid and high clouds associated with a weak east Pacific low pressure
system will generally predominate across the Desert Southwest
through Friday. Otherwise, winds will remain light and diurnal at
all TAF sites. Periods of light and variable winds are also likely.

&&

.FIRE WEATHER...
Saturday through Wednesday:
Conditions will be warm and dry through most of the weekend with
minimum afternoon humidities around 10-20% with good overnight
recoveries. More unsettled weather is expected Sunday night into
early next week with a cold weather system bringing chances of
rain to the lower deserts and good chances of rain and snow to the
high terrain north and east of Phoenix. The system early next week
will also bring breezy to windy conditions Sunday into Monday but
minimum RHs are seen increasing mostly above 20% for that period.
Drier and warming conditions are expected into the middle of next
week.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

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

$$

DISCUSSION...Kuhlman
AVIATION...Hirsch
FIRE WEATHER...Kuhlman

NWS PSR Office Area Forecast Discussion