Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 251133

Area Forecast Discussion
National Weather Service Phoenix AZ
433 AM MST Fri May 25 2018

.UPDATE...Updated aviation and fire weather discussion.


Near normal temperatures and dry weather will persist over the
region through the holiday weekend, though breezy conditions will be
common today and Saturday as a low pressure system moves into
northern Arizona. Warmer temperatures are likely next week with
highs reaching over 100 degrees for most communities.


Early this morning, vapor imagery depicted a closed upper low
spinning just off the California coast, with dry southwest flow
aloft spreading inland and across Arizona. PWAT values from the
latest soundings were 0.3 inches or lower and 1 am surface dewpoints
over the central deserts were mostly in the 20s. IR imagery showed
clear skies area wide. 500mb heights over Phoenix at 5 pm yesterday
were around 586dm, and there will be little change in heights today
as the low continues to spin along the CA coast; thus we can expect
sunny skies along with little change in temps; high temperature in
the Phoenix area will stay near 100 degrees today.

Really, the forecast for the next 7 days will be very similar, as
dry southwest to west flow aloft will dominate on a daily basis,
leading to generally sunny days and clear nights. The main sensible
weather changes will be temperature and wind, as upper level low
pressure systems approach from the west, bring cooler air and
increasing wind, then weaken and lift off to the northeast. The low
just off the California coast is forecast to move inland into the
greater southwest on Saturday, lowering 500mb heights over 60m over
the central deserts and allowing high temps to drop into the low to
mid 90s across the central AZ deserts - and into the upper 80s over
the western deserts. As gradients tighten we will see breezy to
locally windy conditions develop in the afternoon, especially over
wind prone areas in southwest Imperial County. Gusts over 30 mph
will stir up a bit of blowing dust especially from El Centro
westward for much of the night on Saturday night. The low will
weaken and start to lift to the north Sunday but temperatures will
stay below seasonal normals and in the 90s over the lower deserts.

Early next week, as the low moves off well to our northeast, high
pressure will build into the area behind the exiting low, allowing
high temperatures to climb back into the triple digits under sunny
skies. Tuesday will likely be the warmest day of the week, as highs
in the greater Phoenix area climb to around 105 - well above the
normal high of 99 degrees. Slight cooling is then expected through
the middle of the week as another open wave upper trof develops
along the Pacific northwest coast; gradients tighten across the area
and heights gradually taper off. Still, highs will stay in the
triple digits through the end of the forecast period. Phoenix should
see a high near 102 by next Thursday.


South-Central Arizona including KPHX, KIWA, and KSDL:
Minimal aviation concerns today. Easterly winds will shift to the
west around 19Z to 21Z. Between 22Z and 02Z wind speeds will be
slightly elevated with gusts up to 15 to 20 kts possible. Tomorrow
night, downslope winds will take an hour or two longer to
initiate. Skies will remain mostly clear with FEW cloud decks aoa
25 kft in the second half of the period.

Southeast California/Southwest Arizona including KIPL and KBLH:
Westerly winds will remain elevated at both TAF sites through the
period. The breeziest conditions (gusts to 25 to 30 kts) will be
after 20Z, with breezy conditions lasting through 05Z at KBLH and
through 10Z at KIPL. Skies will remain clear.

Aviation Discussion not updated for amended TAFs.


Sunday through Thursday:
Very dry conditions will prevail through the period with no sign
of substantial moisture anytime in the near future. Temperatures
will become seasonably warm after the holiday weekend, with
afternoon highs in the 100 to 105F range, which is about 5F or so
above average. Minimum humidities will mainly be in the single
digits with poor to fair overnight recoveries. Winds will remain
rather light from Sunday through Tuesday. Wednesday and Thursday,
wind speeds will be slightly elevated during the afternoon hours
with gusts up to 15 to 25 kts possible.


Spotter activation will not be needed.




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