Area forecast discussion
National Weather Service Phoenix Arizona
320 PM MST Sat may 25 2013
Synopsis...
dry and warm conditions will persist across the region through the
Memorial Day Holiday weekend. A quick moving low pressure system is
expected to affect the Desert Southwest next Tuesday and Wednesday
bringing cooler than normal temperatures and breezy to windy
conditions. Dry conditions and a warming trend will take place late
next week.
&&
Discussion...
tonight through Monday...
broad upper level low parked over British Columbia and the Pacific
northwest is continuing to eject short wave energy further south
into the Great Basin...eroding a ridge of high pressure that has
been in place over the Desert Southwest for the last few days.
GFS/European model (ecmwf) are both in good agreement that these short wave impulses
will gradually knock heights down and bring slightly cooler
temperatures to our forecast area Sunday and Monday. This will bring
some high clouds and daytime highs that are a couple degrees below
normal across the area by Monday.
Tuesday and Wednesday...
the short waves quickly serve to deepen and broaden the upper level
trough across the western United States...the most southern branch
of energy swinging through Southern California and Arizona with
570-576dm 500mb heights. The trough axis and associated cold front
are currently prognosticated to move through southeast California and
south-central Arizona during the day Tuesday. Breezy to windy
conditions can be expected as early as Tuesday morning...and
continuing into the afternoon hours. Not out of the question for
localized blowing dust and winds to approach advisory criteria...but
current thinking at this time is that wind speeds will be below
advisory strength. The track of this system will definitely bring in
cooler air...helping to dip our daytime highs into the upper 80s to
low 90s for the desert elevations. Moisture availability will also
be on the low side with this trough--well below 4g/kg across
southeast California and south-central Arizona...so the best moisture...
dynamics and precipitation chances will remain confined to northern
Arizona Tuesday and Wednesday. The main effect this far south will
be some increased middle and high cloud cover that will further serve
to mitigate the warmer daytime temperatures.
For late next week...a northwest to westerly upper flow is likely
across most of the western Continental U.S. As the broad trough shifts into the
central United States. This should lead to a moderating of daytime
temperatures for Thursday and Friday with highs returning to around
or slightly above seasonal normals.
&&
Aviation...
south-central Arizona...including kphx...kiwa...ksdl...southeast
California/southwest Arizona...including kipl and kblh...
Few-scattered cirrus expected through Sunday at all taf sites. In the
Phoenix area...wind gusts will reach 20 knots late this afternoon and
early this evening before diminishing around 03z. Typical drainage
flow less than 10 knots expected overnight...followed by a
redevelopment of the upslope flow Sunday afternoon...though somewhat
weaker. Typical southwest and west winds anticipated in southeast California as
well.
Aviation discussion not updated for amended tafs.
&&
Fire weather...
Tuesday through Saturday...
low pressure along the West Coast will begin to push inland over the
Desert Southwest late Monday...then slowly move eastward across the
region on Tuesday and Wednesday. As a result...temperatures are
expected to fall from the middle and upper 90s on Monday into the upper
80s and low 90s on Tuesday and Wednesday across the lower deserts.
Although some increase in the wind speeds can also be expected on
Tuesday and Wednesday afternoon...slightly higher humidities will
keep fire danger values from reaching critical levels. Temperatures
will then recover to near-normal values on Thursday and
Friday...with a return to single digit daytime humidities...and
lighter winds as a dry westerly flow returns to the region. Warming
trend will persist into the weekend.
&&
Psr watches/warnings/advisories...
Arizona...none.
California...none.
&&
$$
Visit US on facebook...twitter...and at weather.Gov/Phoenix
Discussion...Meyers/Kuhlman
aviation...Hirsch
fire weather...Hirsch
