Area forecast discussion
National Weather Service Phoenix Arizona
926 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...
middle morning water vapor imagery reveals abundant dry air across the
region...with a trough extending from low pressure over the Central
Plains westward through The Four Corners. Meanwhile a strengthening
ridge remains in place across the eastern Pacific. At the surface
across Arizona and southeast California...sunny skies prevail with
temperatures in the middle 80s as of 16z.
Conditions today will be very similar to those seen this weekend.
A few distant cumulus to the east with sunny skies elsewhere. Should be
slightly warmer today than yesterday but most spots should stay
below the century mark. Some breeziness will accompany the passage
of the weak trough later this afternoon...although the strongest
winds will likely be confined to the lower Colorado River valley.
Inherited forecast looks on track and no changes necessary.
&&
Previous discussion...
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.
&&
Aviation...
south-central Arizona...including kphx...kiwa...ksdl...
through 03z Tuesday...clear skies. Increasing west wind 15 to 25 knots
between 19z Monday and 03z Tuesday. From 03z Tuesday to 12z Tuesday...clear skies.
West wind 5 to 10 knots.
Southeast California/southwest Arizona...including kipl and
kblh...
through 03z Tuesday...clear skies. Increasing north wind 17 to 27 knots
from 19z Monday to 03z Tuesday. From 03z Tuesday to 12z Tuesday...clear skies.
North wind 5 to 10 knots.
Aviation discussion not updated for amended tafs.
&&
Fire weather...
Wednesday through Sunday...
a large and strong Pacific low pressure system will develop over the
western states north of Arizona. However...gusty west winds with low
humidity will develop every afternoon. Overnight recovery will
become good over portions of southeast California and far southwest
Arizona...but remain 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...leins/Kuhlman
aviation...vasquez
fire weather...vasquez/aj
