Sunrise 5:57 AM   Sunset 7:26 PM Moonrise 11:35 PM   Moonset 8:11 AM

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FXUS65 KPSR 270525 AFDPSR

Area Forecast Discussion National Weather Service Phoenix AZ 1025 PM MST Fri Apr 26 2024

UPDATE
Updated Aviation

SYNOPSIS
Breezy to windy conditions are expected through this evening with the highest wind gusts up to 40 to 50 miles per hour expected in southeast California as a weather system moves through the region.
There will also be a slight chance for rain showers and a few thunderstorms this evening in south-central Arizona, mainly north and east of the Phoenix metro area. The weather system will depart through Saturday, but still with some lingering breezy conditions before high pressure sets in late this weekend and temperatures warm back into the nineties next week.

DISCUSSION
Very breezy and windy conditions are already occurring across the region. The elevated wind speeds and gusts will continue and strengthen in some areas through this afternoon and evening as an upper level jet max passes over southern CA and AZ and as afternoon mixing increases. The dynamic synoptic pattern driving today's weather is detailed well in the air mass satellite product from GOES- West, with the strong upper level jet evident extending northwest through CA and out into the Pacific. Also evident is a vort max southwest of Vegas. This vort max is expected to track eastward through this evening through Central AZ and help generate convection across the region, with slight chances (20-30%) in the AZ lower deserts.

As previously mentioned, a vorticity maximum at the base of the shortwave trough is expected to track pretty much due eastward across central AZ later this afternoon through this evening, triggering elevated convection in the region. The exact track looks to be along the northern county borders of of La Paz and Maricopa counties. This track will keep most of the convection over the northern half of AZ. However, the dynamic forcing will still be close enough to bring slight chances for rain and thunderstorms (10- 30%) to portions of the lower deserts, including Phoenix. There is some uncertainty how far south the convection will extend, but it is conceivable for the convection to extend south through all of Phoenix. The convection will be fast moving, moving westward upwards of 35-45 mph, given the strong winds above the surface. So, do not expect much more than a brief (10 min or less) downpour. As mentioned, the environment will be suitable for isolated thunderstorms, which will pose a lightning threat and strong gusty wind threat. Any storm in South-Central AZ this evening could produce localized wind gusts over 40 mph. HRRR conditional probability of wind gusts over 35 mph in the vicinity of convection this evening is upwards of 50-70%. Main timing of convection in South-Central AZ will be between 6 PM - 12 AM MST.

On Saturday, the trough will quickly move northeastward towards the central Rockies. There will still be some residual breeziness, but noticeably lighter compared to today as peak gusts area wide are expected to remain under 30 mph. There will also be some additional afternoon convection Saturday, but the activity is expected to remain just to the north and east in the AZ higher terrain. Once the trough has fully cleared the Desert Southwest, the ensemble model guidance is in good agreement of low amplitude ridging developing overhead through next week with dry and tranquil conditions prevailing.

Under the influence of the troughing feature, high temperatures today and Saturday will remain below normal with highs across the lower deserts topping out in the low to mid 80s. Beginning on Sunday and continuing through early next week, as high pressure builds over the region, temperatures will be on a strong warming trend. High temperatures on Sunday will rise back up to near normal levels with readings in the mid to upper 80s before rising further into the low 90s on Monday and then into the mid to upper 90s by Tuesday. Not much change in temperatures is expected during the middle to latter half of the week with readings remaining steady state, in the mid to upper 90s, with a low chance (10-20%) that some areas, including Phoenix, reach 100 degrees.

AVIATION
Updated at 0525Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Winds will be the primary weather issue through Saturday night as isold SHRA/TSRA and associated 080-100 AGL cigs currently skirting the far northern parts of the Phoenix metro quickly exit the region around midnight. Low forecast confidence exists regarding exact evolution of winds overnight given the effects of the SHRA creating oscillations between a NW and SW component, but model evidence continues to support a lack of the traditional easterly switch overnight. Renewed gusts around 20kt should be common across the area Saturday afternoon with more usual directional/speed behavior resuming Saturday evening.

Southeast California/Southwest Arizona including KIPL and KBLH: Gusty winds will continue to be the primary weather concern through Saturday evening under mostly clear skies. W/SW winds should continue to gust above 25kt at KIPL into the overnight hours with less gustiness at KBLH. Through the mid/late morning, trends among forecasts suggest a veering to a NW direction during daylight hours Saturday. Periodic gusts may resume Saturday afternoon and evening though forecast confidence regarding the duration of stronger gusts is low.

FIRE WEATHER
On Saturday, winds will trend downward with peak gusts of only 20-30 mph. Rapid drying will result in lower MinRHs Saturday, down to 10- 20% most areas. Temperatures tomorrow will remain below normal with highs only topping out in the low to middle 80s across the lower deserts. Thereafter, a significant warming trend takes place Sunday through early next week with little change in temperatures expected by the middle and latter half of the week. With the warming trend, RH values will trend downward with MinRHs bottoming out at around 10- 15% starting on Monday. Winds through most of next week will be lighter with the typical afternoon upslope breeziness expected.

PSR WATCHES/WARNINGS/ADVISORIES
AZ...Wind Advisory until midnight MST tonight for AZZ532.

CA...Wind Advisory until midnight PDT tonight for CAZ560-563-565>567.

Wind Advisory until 5 AM PDT Saturday for CAZ562.

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