textproduct: NWS Phoenix

UPDATE...Updated 00z Aviation Discussion

KEY MESSAGES

- Temperatures will cool a few more degrees the rest of the week, however remain in a slightly above normal range.

- Breezy conditions will develop along the Lower Colorado River valley and Arizona high terrain on Wednesday, then return to the area over the weekend.

SHORT TERM /Today through Thursday/

Early afternoon objective analysis depicts a 590dm H5 anti-cyclone centered over western New Mexico slowly being dislodged and de- amplified by the combined effort of subtropical energy lifting north from the Baja into the SW Conus and stronger troughing entering the Pacific NW. As such, H5 heights within the forecast area have eroded into a 584-588dm range providing slight cooling versus yesterday, and most pronounced over the western CWA. Otherwise, only a narrow midlevel moisture band associated with Baja shortwave will pass through the region with some virga (and possible erratic winds) as a result.

Over the next couple days, high pressure aloft will further be displaced eastward with a progressive flow pattern resulting in additional modest heights falls across the SW Conus. Some measure of weak troughing/quasi-zonal flow will prevail over the region with H5 heights generally hovering in a 580-584dm range. Ensemble guidance spread is rather narrow leading to excellent forecast confidence of high temperatures mostly 6F-8F above normal, while clear skies and a dry airmass promote efficient nocturnal cooling and lows not far from climatology. This pattern of weak troughing/height falls will support deep mechanical mixing and gusty afternoon winds, though nothing unusually strong for mid May.

LONG TERM /Friday through Tuesday/

The weather pattern later this week is expected shift to a more zonal westerly dry flow pattern, but with some influence from passing troughs to our north. The drying flow will result in clear to mostly clear skies Friday-Saturday with temperatures remaining quite stable averaging 5-7 degrees above normal. Ensembles are currently favoring a larger Pacific trough moving through the Pacific Northwest this weekend bringing lower heights as far south as the Southwestern U.S. NBM/WPC temperature guidance suggests daytime highs falling back more into the upper 90s by around Sunday. Otherwise, daytime gusty winds will return to the region over the weekend in association with the aforementioned trough passage.

AVIATION

Updated at 2325Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Occasional gusty winds under mid/high cloud decks will be the primary aviation weather issue throughout the TAF period. Winds through this evening will maintain a westerly component with occasional gusts between 20-25 kts through the early to mid- evening hours before gusts subside overnight with an easterly switchover anticipated. Before the typical westerly switchover Wednesday afternoon, a period of southerly crosswinds between 8-12 kts is anticipated during the late morning/early afternoon hours. Occasional gusts upwards of 20-25 kts are anticipated once again Wednesday afternoon, strongest near KIWA.

Southeast California/Southwest Arizona including KIPL and KBLH: Periods of gusty winds under mostly clear skies will be the primary aviation weather issue throughout the TAF period. At KIPL, southeasterly winds will switch to a westerly component early this evening and remain out of the west throughout the rest of the period. At KBLH, winds will generally maintain a south to south- southwest component throughout the period. Wind gusts between 20-30 kts will be common through early this evening before weakening overnight aob 10 kts. Another period of gusty winds upwards of 20-25 kts is anticipated once again Wednesday afternoon.

FIRE WEATHER

Hot, dry, and locally breezy to windy conditions will result in elevated fire weather potential this afternoon across the Lower CO River Valley. Wind gusts of 20-30 mph along with RHs 7-10% are expected across the Lower CO River Valley. Elsewhere today, winds will be lighter but with afternoon gusts of 15-20 mph possible. Wednesday will bring another round of breezy winds over southeast California and the Arizona high terrain with elevated fire weather conditions again a possibility. Temperatures today will be 10-15 degrees above normal dropping to 5-8 degrees above normal starting Wednesday. Winds will diminish starting Thursday, but very dry conditions will continue to prevail.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Extreme Heat Warning until 8 PM MST this evening for AZZ537-540- 542>544-546-548-550-551.

CA...None.