Area forecast discussion
National Weather Service Phoenix Arizona
900 PM MST sun may 19 2013
Synopsis...
a series of cool low pressure systems will continue to move into the
western states mainly north of Arizona through Monday. Near normal
temperatures...mostly clear skies...and somewhat breezy afternoons
are expected. A high pressure system will build back into the region
Tuesday through Friday...and except for some high clouds at times...
afternoon temperatures on the deserts will warm back into the 100 to
103 degree range.
&&
Discussion...
cyclonic flow persists this evening across the intermountain west
and southern rockies...helping to fuel the organized thunderstorm
activity further east in the plains. Upstream in the Great Basin...a
weak short wave trough has its aim on The Four Corners Monday.
Biggest impact across the forecast area will be an increase in
wind...particularly down the Colorado River valley late tonight through
Monday afternoon. In the short-term...only minor adjustments to the
temperatures and dewpoints were needed. Otherwise...forecast remains
on track.
&&
Previous discussion...
broad northwesterly flow continues across the intermountain west
this afternoon...as a large trough continues to intensify across the
Central Plains and a ridge strengthens over the eastern Pacific.
Almost an identical regime as yesterday...slightly below normal pw\s
across the region with some isolated high terrain showers and
thunderstorms across northern Arizona. Across the deserts
however...skies remained mostly clear as of 21z.
One more day of northwesterly flow on tap for the region and not
surprisingly...the forecast for tomorrow will be virtually identical
to yesterday and today. Mostly sunny skies and dry weather expected
with temperatures slightly above normal.
The Pacific Ridge will weaken somewhat as it moves onshore
Tuesday...yet it will still manage to heat the bl about 1c each day
through Thursday. Temperatures in the lower 100s at all desert locations
looks like a safe bet later this week although with normal highs in
the upper 90s...this isn\t too unheard of for middle/late may.
Previous discussion...
Saturday and Sunday...
another large Pacific low pressure system will move into the western
states late Friday through Sunday...mainly northwest of Arizona. Gusty
afternoon winds are expected this period...along with temperatures
falling back to near seasonal normals.
&&
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...Hirsch
previous discussion...leins/vasquez
aviation...Hirsch
fire weather...aj
