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FXUS65 KPSR 170941 AFDPSR

Area Forecast Discussion National Weather Service Phoenix AZ 241 AM MST Fri May 17 2024

SYNOPSIS
High pressure will increase over the region into the weekend leading to even warmer temperatures with most lower desert locations seeing highs top out at or just over 100 degrees today and Saturday. A dry weather disturbance is then expected to move through the region during the first part of next week eventually leading to temperatures closer to normal through the middle of next week. Clear to mostly clear skies are expected each day, while breezier conditions are likely Sunday through early next week.

DISCUSSION
The compact vort max that brought yesterday's convection to portions of south-central Arizona has now moved into northern Mexico with upper level ridging quickly filling in from the west.
As H5 heights rise to between 582-584dm by tonight and drier air slowly works through the region, modest warming will be realized with daytime highs peaking today across the western deserts between 100-103 degrees to the upper 90s to around 100 degrees in the Phoenix area. The ridge axis will then quickly move to the Arizona/New Mexico border Saturday morning as a weak shortwave trough approaches southern California. Temperatures Saturday should already start to cool off a couple degrees over the western deserts, but warm another couple degrees across the south-central Arizona lower deserts with highs peaking in the lower 100s in Phoenix. Both days should present a Moderate HeatRisk for a good portion of the lower deserts.

A very weak shortwave trough is forecast to quickly move through the region Saturday night/Sunday morning lowering heights aloft enough to drop daytime highs Sunday into the upper 90s. Winds should also pick up by Sunday with an increasing gradient with afternoon/evening gusts upwards of 25-30 mph in some places.
Further cooling and continued breezy conditions are then expected during the first part of next week as a larger Pacific trough drops south southeastward through the Great Basin into the Desert Southwest Monday into Tuesday. This should drop H5 heights down to between 572-578dm and lower 850mb temperatures 2-3C across the region. By Monday, NBM forecast highs drop to around 95 degrees with some lower desert areas as low as the lower 90s, or right within the normal range for this time of year. Aside from higher clouds on Monday, the trough will be dry with no realistic rain chances, even over the Arizona high country. The weather pattern going into the latter half of next week should keep broad upper level troughing in place, but a slight retrograding of the trough by next Friday or Saturday may result in some ridging building back into the Desert Southwest from the southeast. If this holds true, temperatures will likely start to creep back closer the upper 90s by next weekend.

AVIATION
Updated at 0544Z.

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

No aviation weather concerns are expected through the TAF period.
Winds through the TAF period will favor more typical light, diurnal tendencies with periods of variability and occasional afternoon gusts to around 15-20 kts tomorrow. FEW clouds aoa 12 kft will give way to SKC conditions later tonight.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation weather concerns are expected through the next 24 hours. Winds at KIPL will favor a westerly component throughout the period with extended periods of light and variable winds beginning tomorrow morning. At KBLH, southerly winds will persist with elevated speeds sustained around 10-15 kts continuing into the overnight hours before weakening and gusts to around 20 kts tomorrow afternoon. Otherwise, SKC conditions will persist.

FIRE WEATHER
High pressure will settle over the region today into the weekend with warmer temperatures and drying conditions. This will lead to daily highs around 100 degrees across the lower deserts and MinRHs falling to around 10% through Saturday. Breezy conditions with afternoon gusts up to around 20 mph over the eastern districts to 25 mph across the western districts can expected through Saturday before increasing further for Sunday and Monday. The combination of low RHs and breezy afternoon winds will likely result in elevated fire danger through at least the weekend where there are abundant dry fine fuels. A dry weather system is then expected to move through early next week resulting in temperatures closer to normals, but continued breezy conditions and MinRHs around 10%.

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

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