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FXUS65 KPSR 182325 AFDPSR

Area Forecast Discussion National Weather Service Phoenix AZ 425 PM MST Thu Apr 18 2024

UPDATE
Updated Aviation section.

SYNOPSIS
Dry conditions and above normal temperatures will prevail through early next week. The warmest days over the next week are expected to be Sunday and Monday, with a few warmer locations potentially reaching 100 degrees. Otherwise, high temperatures in the low to mid 90s will be common across the lower deserts through next Tuesday before a gradual cooling trend takes hold during the latter half of next week. A weak disturbance will pass over the Desert Southwest to end this week, bringing widespread breezy conditions tomorrow.

DISCUSSION
A deck of high clouds is currently streaming over the region ahead of a weak shortwave trough as it moves eastward towards the Southern California Coast. With a ridge of high pressure in place over the Desert Southwest, high temperatures are still expected to approach the low-to-mid 90s across much of the lower deserts today despite the cloud cover. Heights aloft will become slightly depressed as the shortwave traverses the region late tomorrow into Saturday, but daily afternoon high temperatures will remain relatively stable tomorrow and Saturday under sunny skies. The main sensible impact of this shortwave will be widespread breezy conditions (gusts to 15-25 mph) tomorrow afternoon, with the strongest winds anticipated in Imperial County in the evening. Gusts across the lower elevations of central and eastern Imperial County will likely approach 30-35 mph late tomorrow afternoon into the evening, with even 90th percentile HRRR gusts remaining below 40 mph across much of the County except over the highest elevations in the far southwestern corner.

Ridging will prevail once again in the wake of the shortwave trough with forecast highs warming into the mid-to-upper 90s Sunday and Monday. A few warmer locations may even approach the century mark during this time, though probabilities for reaching or exceeding 100 degrees remain low (up to 10-30%). Temperatures may not be exceeding 100 degrees at this point, but the proper heat safety precautions should still be exercised as temperatures warm up. Widespread Minor to at times locally Moderate HeatRisk will continue through the next week. Global ensembles then show a deeper trough affecting the Desert Southwest during the latter part of next week, though considerable uncertainty exists. For now, the NBM shows a cooling trend for the latter half of next week with the potential for temperatures to cool back down to near normal readings by along with increased breezy conditions.

AVIATION
Updated at 2325Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Anticipate surface winds to take on a westerly component between 00Z-01Z. Sustained winds are expected to remain below 10kts for the most part but gusts up to 15kts will be common between 00Z-02Z. A number of high resolution models are indicating a temporary shift to N/NWly between roughly 02Z-06Z but with speeds AOB 8kts. This is reflected in TEMPO groups in the TAFs.
Otherwise, anticipate a slow trend toward nocturnal downvalley/drainage patterns starting after about 05Z. Daytime winds Friday will follow a similar pattern as today with a period of southerly winds followed by a mid to late afternoon onset of southwesterly. As for sky cover, cirrus will thin out after midnight with clear skies the rest of the TAF period.

Southeast California/Southwest Arizona including KIPL and KBLH:

At KIPL, light southeasterly winds will shift to westerly early in the TAF period. Strong winds are not expected with sustained speeds below 15kts. Westerly winds are expected to prevail the rest of the TAF period but with fluctuations in speed. At KBLH, southerly winds with gusts up to 20kts are expected to shift to southwesterly early in the TAF but with less gustiness. Light and variable winds begin to develop by around 06Z followed by minor southerly breeziness (gusts 15-20kts) Friday afternoon. As for sky cover, cirrus will thin out before midnight with clear skies prevailing the rest of the TAF period.



FIRE WEATHER
Dry weather will continue through at least the next couple of days. Above normal afternoon temperatures will continue through the remainder of the week as lower desert highs top out in the low to mid 90s. Winds will remain light today with typical afternoon breezes into the teens at times. A weak weather system will lead to afternoon gusts increasing Friday to 15-25 mph for many areas, while areas across Imperial County potentially see gusts in excess of 30 mph Friday evening. Min RHs will continue to fall into the 5-15% range each day.

PSR WATCHES/WARNINGS/ADVISORIES
AZ...None.
CA...None.

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