Area forecast discussion
National Weather Service Phoenix Arizona
237 am MST Monday may 20 2013
Synopsis...
stronger high pressure will settle into the region over the next
couple days with continued dry weather and above normal temperatures
through middle week. Clear skies and somewhat breezy afternoons are
expected nearly every day. A deep low pressure system will move
southeast into the Great Basin by late week allowing a slight
cooling trend. The dry conditions will continue through the coming
weekend while temperatures fall back to around seasonal normals
starting late this week.
&&
Discussion...
the large trough stretching from the central rockies into the
western Great Lakes will finally see the western periphery erode as
the eastern Pacific Ridge nudges its way eastward into the Great
Basin by tonight. Surface high pressure currently stretching from
the Pacific northwest into the Great Basin will quickly slide
southward today bringing a frontal boundary through the our area.
The front will come down the lower Colorado River valley by late
morning with increasing northerly winds and drier air behind the
front. Breezy to windy conditions with gusts to around 30 miles per hour are
expected starting late this morning down the lower Colorado River
valley and expanding eastward through south-central Arizona late
this afternoon.
As the upper ridge builds in through Tuesday...will see an increase
in temperatures with Lower Desert readings around 100f both Tuesday
and Wednesday. The ridge axis will pass through Tuesday night with a
return to southwesterly upper flow thereafter. Models continue to
advertise a deep closed low moving into the Pacific northwest on
Wednesday and then drifting southeastward into the Great Basin for
late this week. Model consensus is fairly high now that the
expansiveness of the upper low will affect the Desert Southwest at
least partially...resulting in slightly cooler conditions. Have
lowered temperatures several degrees starting Thursday and through
the weekend with the coolest temperatures across western portions of
the County Warning Area. There is still some question on how far south this closed
upper low will get...with a more southern solution resulting in
cooler temperatures and a northern solution in warmer temperatures.
Either way the region will remain under a dry westerly flow with
little in the way of any cloudiness. Most days will also see fairly
breezy afternoon conditions...but gusts should generally remain
under 30 miles per hour. The large scale pattern beyond this coming weekend
suggests a trough/ridge/trough pattern across the Continental U.S. Which will
likely keep our temperatures at or slightly below normal across the
Desert Southwest into early next week.
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Aviation...
south-central Arizona...including kphx...kiwa...ksdl...
more of the same expected Monday with clear skies and drainage flow
giving way to a westerly flow during the afternoon. Gusts could
reach as high as 20-25 knots through 01z Tuesday before subsiding
01z-03z.
Southeast California/southwest Arizona...including kipl and kblh...
stronger winds will be funneled down the Colorado River valley overnight
and into Monday morning as a low pressure system treks towards The
Four Corners. The windy conditions will be most pronounced at kblh
with gusts occasionally reaching 25-30 knots between 15z and 22z
Monday. Winds will decrease thereafter...likely subsiding below 10
knots as early as 02z Tuesday.
Aviation discussion not updated for amended tafs.
&&
Fire weather...
Wednesday through Sunday...
high pressure will weaken Wednesday and be displaced by a trough of
low pressure over the western states...centered over the Pacific
northwest. This will lead to breezy to windy conditions at
times...most noticeably over southeast California...along with
slightly cooler temperatures. Minimum humidities will remain low.
Overnight recovery will become good over portions of southeast
California and southwest Arizona...remaining poor elsewhere. At this
time...conditions are expected to remain below critical thresholds.
&&
Psr watches/warnings/advisories...
Arizona...none.
California...none.
&&
$$
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Discussion...Kuhlman
aviation...Hirsch
fire weather...aj
