Scientific Forecaster Discussion
fxus65 kpsr 282153
Area forecast discussion
National Weather Service Phoenix Arizona
253 PM MST Wed Jun 28 2017
a dry airmass will remain over the region through the rest of the
week with temperatures moderating closer to average. Though high
temperatures will finally drop below 110 degrees, readings will
still end up in a slightly above normal range through early next
week. Skies will remain mostly clear as the monsoon wind pattern
has yet to be established and storm activity will stay well south
the center of the subtropical ridge remains south of the region
with large scale troughing pushing across the Pacific northwest
and the Great Basin. This is resulting in enhanced dry west to
southwesterly flow aloft and a significant decrease in 500 mb
heights. The dry air advection was very evident on this mornings
12z Phoenix sounding, where precipitable water values were .65 inches less than
monday's sounding. High temperatures will finally stay below 110
degrees over many desert locations today and these "cooler"
temperatures will continue through the rest of the week. In
addition, dry air and clear skies will lead to decent radiational
cooling overnight. This will allow temperatures to drop into the
70s over many desert locations with the exception of central parts
of Phoenix which will be a few degrees warmer due to the "urban
Later this week, 500mb heights do begin to increase a bit as the
troughing to our north shifts over the central and eastern U.S.
After highs just below 110 through Friday, we should see a couple
degrees of warming on Saturday with the higher heights resulting
in highs around 110. Although 500mb heights stabilize this weekend
near 592dm and stay there into early next week, a slight boost in
low level moisture (afternoon surface dewpoints 35-40 degrees)
should keep highs just below 110 Sunday through Tuesday. This
moisture uptick will however still be insufficient for any monsoon
activity to be seen across the area as both the GFS and European
are in good agreement keeping low level flow either out of the
west or north through next Wednesday. There are indications we may
manage to see a switch to southeasterly low level flow late next
week which could be enough to bring at least a low grade monsoonal
moisture flow out of northern Mexico.
south-central Arizona including kphx, kiwa, and ksdl:
Expect west winds near 10kt with periodic gusts of 15-17kt through
the early evening. Tonight the winds will become lighter and follow
normal diurnal shifts. Clear to mostly clear skies are also expected
throughout the period.
Southeast California/southwest Arizona including kipl and kblh:
Generally breezy winds will favor the southwest and west at 10-12kt
with gusts of 17-20kt this afternoon and into tonight. Late
tonight, winds will become lighter and favor normal diurnal
shifts or become light and variable. Otherwise expect clear skies
throughout the period.
Aviation discussion not updated for amended tafs.
Saturday through wednesday:
A very hot and dry weather pattern will persist throughout the
period. Maxt's will remain very hot and generally range from near
seasonable to above normal values through Wed. In addition, min relative humidity
values will remain mostly in the single digits, or below 15 percent
at the most, throughout the lower deserts. Poor to fair overnight
recoveries should improve to fair beginning Tue. Seasonably breezy
west and southwesterly winds can be expected each afternoon with
gusts of 15-17mph.
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