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FXUS65 KPSR 192202 AFDPSR

Area Forecast Discussion National Weather Service Phoenix AZ 302 PM MST Sun May 19 2024

SYNOPSIS
Temperatures this week will be near normal as a couple weather systems pass through the region, but mainly to the north of our area. These systems will lead to breezy to windy conditions during the afternoon and evening hours, with the highest winds and greatest impacts expected on Monday. There is a slight chance for some virga and/or sprinkles in south-central AZ tomorrow afternoon, otherwise dry conditions continue into next week.

DISCUSSION
Analysis of upper-level water vapor imagery this afternoon reveals a closed low off the coast of southern California along with a trough digging to the southeast in the Pacific NW. Ahead of these systems, wind gusts this afternoon and early evening are expected to easily reach into the mid 20s areawide to 30-35 mph across portions of southeast California. These winds combined with low humidity will lead to elevated to critical fire weather conditions today. The aforementioned closed low will move on shore during the overnight hours and get swept up in the aforementioned trough as it continues to dig to the SE. This system will bring a cold front to the area tomorrow, knocking afternoon temperatures down to near normal (about 5 degrees cooler than today's forecasted high temperatures). Moisture will be limited, but some virga and/or sprinkles will be possible in south-central Arizona during the early afternoon as the cold front moves through. Winds will be the main concern tomorrow afternoon and early evening and will likely reach 25-35 mph across south-central Arizona and 30-45 mph across southeast California and the Lower CO River Valley. Winds may briefly gust up around 40 mph in south-central AZ along the front as it moves through in the early afternoon. These winds combined with the low humidity will lead to another day of elevated to critical fire weather conditions.

Broad troughing over Western CONUS will persist through next weekend along with a few shortwaves sliding to our north throughout the week. This will help keep temperatures right around or even slightly below normal heading into Memorial Day Weekend. Aside from the slight chance of some virga and/or sprinkles tomorrow afternoon, dry conditions will continue through next weekend. Global ensemble models are in fairly good agreement that heights aloft will return to zonal flow and then start to rise early next week. This will allow for another warming trend and push temperatures back above normal.

AVIATION
Updated at 1720Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Persistence of typical diurnal wind tendencies is expected through the TAF period at all terminals. Winds currently beginning their veer to the west/southwest. Typical late afternoon gusty westerly winds as high as 20 to 25 kts. Winds will subside mid evening with the typical diurnal tendency back to east southeast overnight into early Monday. Some high clouds will begin to move into the area late tonight. Some thickening and lowering cloud bases expected toward 18z but still remaining above 12k feet.

Southeast California/Southwest Arizona including KIPL and KBLH: Winds will increase from the south-southwest with afternoon speeds increasing with gusts up to 20-30 kts. Some lighter winds overnight, before increasing again and becoming gusty again bu late Monday morning. SKC will prevail through this evening followed by FEW-SCT high clouds developing Monday morning.

FIRE WEATHER
A cold front will move through the region tomorrow knocking temperatures down to near or slightly below normal along with brining strong, gusty winds to the region. While some virga/sprinkles will be possible in south-central Arizona, there is no chance for wetting rain with this cold front. Throughout the week, MinRH will be in the single digits for lower elevations and in the teens across the higher terrain. Overnight recoveries will be poor to fair and in the 20-40% range. Wind speeds will be the highest on Monday with widespread gusts as high as 30-35 mph. This combined with the low RH and dry fine fuels will lead to near critical thresholds. Land managers should be cautious for rapid, uncontrolled spread of any ongoing fires or new starts Monday. For the remainder of the week, afternoon gusts will be in the 20-25 mph range, which will lead to slightly elevated fire danger.

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

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