textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- An Extreme Heat Warning remains in effect for the Phoenix Metro area through early this evening with temperatures topping out between 105 to 107 degrees.

- Breezy conditions are anticipated along the Lower Colorado River valley today and Wednesday and over the AZ high terrain on Wednesday. - A more noticeable cooling trend starting Wednesday will drop high temperatures into the upper 90s to around 100 degrees, lasting through the upcoming weekend.

SHORT TERM /TODAY THROUGH WEDNESDAY/

A strong upper level ridge with near climatological record H5 heights is positioned across the Desert Southwest. Additionally, a weak shortwave trough is also located over central Baja. Southeasterly flow in between the two systems did result in some scattered convection across northern Mexico yesterday along with some remnant moisture from the convection making its way northwestward into southern Arizona. This moisture may result in some morning mid level clouds, but overall today will again be sunny to mostly sunny for most locations.

As the weak shortwave continues to move northward into southern California later today, height falls across the western deserts will bring some slight relief from yesterday's near 110 degree highs as readings mostly top out between 102-106 degrees. The ridge will remain more dominant across Arizona resulting in highs of 105-107 degrees in the Phoenix area where an Extreme Heat Warning remains in effect. The southeasterly flow continuing across the area through the rest of today may allow for some widely isolated convective showers across southeast Arizona and likely some clouds into the south-central Arizona lower deserts by this evening. Southerly breezy to locally windy conditions will also affect portions of southeast California and southwest Arizona this afternoon with gusts as high as 25-30 mph in some locations.

By Wednesday morning the weak shortwave is forecast to have moved into central California and western Nevada as another stronger Pacific wave moves eastward across the Pacific Northwest. Both systems will combine into a larger trough with a trailing trough axis eventually making its way into our region by Thursday. At the same time, it will completely displace the ridge to the east of our region allowing for modest height falls and cooling temperatures. Forecast highs for Wednesday drop into the upper 90s to just over 100 degrees across the lower deserts.

LONG TERM /THURSDAY THROUGH MONDAY/

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 for Thursday-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.

AVIATION

Updated at 1130Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Occasionally gusty SSW-W winds this afternoon/evening will be primary weather issue through the TAF period under FEW-SCT mid and high cloud decks. Winds this morning should generally favor an easterly component, but a period of variability or earlier than usual SW switch cannot be ruled out. Confidence is moderate to good that SSW-SW winds will become favored across the terminals by 18-20Z, with occasional gusts to around 15 kts developing during the afternoon. During the evening, confidence remains high enough to include TEMPO stronger SW-W gusts to around 20 kts, as Hi-Res guidance continues to show a signal similar to a gulf surge. However, virga to the south/southeast of the Phoenix airspace could conceivably cause some erratic wind behavior and gusts from a more southerly direction around the same time, with a higher likelihood of that impact at KIWA.

Southeast California/Southwest Arizona including KIPL and KBLH: Periods of gusty winds with directions mostly out of the south at KBLH and varying between SE and W at KIPL will be the primary aviation concern through the next 24 hours under FEW mid to high cloud decks. Southeast winds will be favored throughout the day at KIPL, switching SW-W by 02-03Z this evening. Speeds will increase through the morning hours, with gusts likely developing by the afternoon to around 20 kts at KIPL and 25 kts at KBLH. After the SW-W switch at KIPL in the evening, confidence is low on whether gusts will develop and exactly when they will subside, but winds should remain out of a prevailing westerly direction overnight. Gusts at KBLH should subside around sunset.

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.