textproduct: NWS Phoenix

KEY MESSAGES

- Breezy to locally windy conditions over portions of Southwest Arizona and Southeast California will gradually diminish through the rest of the afternoon.

- Freeze Warnings will be in effect Saturday morning, with more widespread coverage of freezing temperatures expected than that of last night across the typically prone rural and low lying areas.

- Below normal temperatures through Saturday will then warm near to above normal by Sunday and remain in an above normal category during the upcoming work week.

- Dry conditions will prevail across the region through at least the next week.

SHORT TERM /TODAY THROUGH SATURDAY/

Current water vapor satellite imagery and 500 mb RAP analysis shows the forecast area under northerly flow, turning northwesterly towards Southern AZ, as the region is positioned between an upper level ridge axis just off the West Coast and an upper level low that is centered near the OK/TX panhandle. A vorticity lobe sliding south along the backside of the upper low was able to squeeze out some very light precipitation over the Eastern AZ high terrain this morning, despite very dry air in place over the region. PWATs have rapidly dropped, now mostly below 0.30" across the forecast area and still falling as a dry, continental air mass filters into the region from the north. NAEFS and ENS advertise mean PWATs hovering around 0.10-0.15" through Saturday, which is below the 10th percentile of CFSR climatology and below the 1st percentile for a few areas.

As synoptic-scale temperature and pressure gradients slacken over the area today, anticipate lingering breeziness, especially along/near the Lower Colorado River Valley and portions of SE CA and SW AZ to decrease through the remainder of the afternoon. Wind Advisories were extended through 4 PM PST/5 PM MST as gusts in excess of 40 mph persist over parts of the area. A gust up to 53 mph was reported at Blythe Airport late this morning. Very dry air, calm winds, and clear skies will combine for efficient radiative cooling tonight into early Saturday morning, and so we will likely see the coldest temperatures of the winter so far across much of the CWA. As such, Freeze Warnings will be in effect and more widespread in coverage Saturday morning than they were this morning, covering many of the typical freeze-prone rural valleys and low-lying areas. You should be prepared to protect the 4 P's (people, pets, plants, and pipes) from the cold, especially if you live within the areas covered by Freeze Warnings. After what will likely be the coldest morning of the season so far, afternoon highs Saturday are only forecast to reach the lower to middle 60s across the lower deserts, at least a few degrees below daily normals.

The upper level pattern will shift this weekend, with almost all ensemble guidance showing a piece of energy breaking off the trough to our east and retrograding over Sonora, eventually settling over/near the Baja Peninsula as early as Saturday night, while the East Pacific ridge shifts slightly eastward over the Western US. The resultant upper level pattern resembles a rex block, which should be maintained for a few days. Characteristic of a rex block, ensembles advertise an easterly jet forming in between the cutoff low and high pressure to the north forming somewhere over the Desert Southwest. At the surface, NAEFS/ENS mean SLP will reach near climatological maximum values at times over the Desert Southwest, with lower SLP offshore, forcing a prolonged period of northeasterly flow which may become locally breezy during the afternoons this weekend.

LONG TERM /SUNDAY THROUGH NEXT FRIDAY/

Global ensemble members continue to be in good agreement on the overall synoptic pattern for next week. A blocking pattern will develop by the end of the weekend with high pressure returning to Western CONUS. The center of this high will initially be off the coast of central CA, and will eventually migrate over northern CA during the beginning of the workweek. This blocking pattern will continue through next week, with the high pressure strengthening through the first half of next week. The high currently looks to maximize during the middle of the week, with H5 heights over our region around 582-585 dm. With the high pressure strengthening through the middle of next week, temperatures will gradually warm as a result. On Sunday and Monday afternoon high temperatures are forecasted to be in the upper 60s to low 70s across the lower deserts and in the mid 50s to low 60s across the higher terrain. Then on Tuesday, afternoon high temperatures will warm to the low to mid 70s across the lower deserts and will be in the 60s across the higher terrain. Temperatures will warm even more to end the workweek (maximizing Wednesday/Thursday) , with afternoon high temperatures in the mid to upper 70s to near 80 degrees across the lower deserts and in the mid 60s to low 70 degrees across the higher terrain. Morning low temperatures will also warm, going from the upper 30s to low 40s (low to mid 30s) across the lower deserts (higher terrain) on Sunday to the mid 40s to low 50s (upper 30s to low 40s) across the lower deserts (higher terrain) to end the workweek. Additionally, with high pressure building back over the region, dry and tranquil weather conditions return this weekend and continue through next week.

AVIATION

Updated at 1735Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation weather concerns under generally clear skies can be expected throughout the TAF period. Winds through the majority of the TAF period will fluctuate between the N/NE with periods of light variability during the overnight and early Saturday morning. Wind speeds will generally remain under 10 kts, although some afternoon gusts in the upper teens will be possible.

Southeast California/Southwest Arizona including KIPL and KBLH: The main aviation weather concern throughout the TAF period will be strong winds out of the north/northwest through early this evening. At KIPL, winds will generally be out the north through early this evening, before shifting out of the west by late this evening through the overnight hours. At KBLH, winds will generally be out of the north. Through late afternoon, gusts upwards of 25 kts can be expected at KIPL and upwards of 30-35 kts at KBLH. Wind speeds across both sites will gradually diminish by early this evening. Generally clear skies will persist throughout the period.

FIRE WEATHER

Temperatures remain below normal today and Saturday, followed by a warming trend back into an above normal category by the beginning of next week. The cold front that moved through yesterday has ushered in a much drier air mass across the area. MinRH values have fallen into a 15-35% range and will remain in that range through next week, with overnight recoveries generally between 40-70%. Yesterday's system has also brought breezy to locally windy conditions to the region, with the highest winds across portions of Southeast CA and the Lower CO River Valley. Most areas will see northerly wind gusts of 20-35 mph, but gusts upwards of 40-55 mph gusts remain possible across portions of the western districts for the rest of the afternoon. Winds will taper off later this afternoon and evening. Wind speeds will return to more seasonable levels this weekend, with locally breezy north to northeast winds during the afternoons.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Wind Advisory until 5 PM MST this afternoon for AZZ530.

Freeze Warning from midnight tonight to 9 AM MST Saturday for AZZ530-533-534-551>554-556-560>562.

CA...Wind Advisory until 4 PM PST this afternoon for CAZ560-564-565- 568>570.

Freeze Warning from 11 PM this evening to 8 AM PST Saturday for CAZ560-569.