Area Forecast Discussion
Issued by NWS Phoenix, AZ
FXUS65 KPSR 250441
Area Forecast Discussion
National Weather Service Phoenix AZ
941 PM MST TUE MAY 24 2016
A large region of low pressure will continue over the Western States
through the weekend bringing overall cooler than normal temperatures
and dry conditions. A more compact low pressure system will move
through Wednesday bringing gusty winds to much of the area. Building
high pressure for next week will likely bring a warming trend pushing
highs to near 100 degrees for the lower deserts by the middle of
Mostly quiet evening across the forecast area with the only
noticeable weather in the form of continued breezy to gusty winds
especially along and west of the Colorado River Valley. Water vapor
loops this evening continue to indicate negative height anomalies and
low pressure circulations over the Intermountain West. One stronger
vort max, and accompanying upper jet support, has continued to
circulate down the CA coast this evening with the circulation just NW
of the L.A. Basin. Upper jet rounding the base managed to lift some
moisture and generate high level clouds downwind of the Peninsular
Ranges. Minor updates were worked into the Sky grids to capture that
cloud development. Upper low circulation will swing through the state
during the day tomorrow, promoting breezy to locally windy conditions
for most. Updates needed this evening were to trend dewpoint and sky
cover forecasts to current observations.
.PREVIOUS DISCUSSION /ISSUED 146 PM MST/PDT/...
Early afternoon water vapor imagery shows the slow moving upper
level low over the Western United States with the main low
circulation just off the central California coast. Dry southwesterly
flow and clear skies continue to affect the Desert Southwest as the
upper low nears the region. Pressure packing has increased since
yesterday resulting in some breeziness across the region, but the
strongest pressure gradients and winds will affect the region
Wednesday. The main low circulation is forecast to dive southward
tonight before making a sharp turn to the east through southeast
California during the daytime hours Wednesday. Strong height falls
and the increased pressure gradient will increase winds Wednesday
with some gusts approaching 35 mph. Can`t rule out some patchy
blowing dust, but not expecting any widespread impacts.
Despite strong UVV associated with this compact low circulation,
the dry nature of this system (PWATS less than a half an inch)
should only allow for a slight chance of a stray shower/thunderstorm
across JTNP Wednesday afternoon/evening. Temperatures will take a
slight dip across our western zones on Wednesday and then over
south-central Arizona on Thursday, but for the most part highs should
mostly top out in the middle to upper 80s through Thursday.
Once the upper low exits the region later Thursday, weaker
northwesterly flow aloft will take over through the weekend. Upper
level heights will remain fairly stable through this period and
temperatures will remain below climatological normals. Though model
ensemble spread increases for the early to middle of next week, there
are indications a Pacific ridge will build off the West Coast
displacing the large scale troughing pattern into the middle part of
the country. This potential pattern change would likely bring a
warming trend for the beginning of June and highs again topping 100
degrees across the deserts.
South-Central Arizona including KPHX...KIWA and KSDL...
Westerly winds to linger a little later in the evening that when is
typical as another low pressure system approaches the area. Little
moisture with this system will keep conditions dry and skies mostly
clear, but support windy conditions from the late morning through
evening. Easterly winds to transition into the airfields overnight
somewhere between 09-11z. More noticeable transition from E through S
to W will occur tomorrow. Widespread gusts 20 to 25kts will be
possible by the afternoon from the W-SW.
Southeast California/Southwest Arizona including KIPL and KBLH...
Another low pressure system and accompanying strong jet streak will
promote prolonged periods of strong winds for KIPL and KBLH. West to
southwest orientated winds sustained 15 to 20kts will continue
overnight. A brief lull midday may develop for the terminals with
speeds dropping around 10kts. Gusty winds to return for the afternoon
with 30kt gusts possible. Skies will be mostly clear, save for
periods where strong ridgetop and jet level winds create a few hours
of cirrus blow-off from the mountains to the west.
Aviation Discussion not updated for amended TAFs.
Friday through Tuesday...
With dry northwesterly flow aloft on Friday expect high temperatures
to warm into the mid 90s on Friday with little change in the daily
highs through Tuesday. Expect minimum relative humidities in the
lower to upper teens on Friday to gradually dry to the 8 to 14
percent range by Sunday along with fair overnight recoveries.
Occasionally breezy southerly and southwesterly winds can be expected
each afternoon with gusts of 15 to 20 mph, although on Saturday
afternoon the winds will be stronger with gusts of 20 to 25 mph.
.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected.
Visit us on Facebook...Twitter...and at weather.gov/phoenix