textproduct: NWS Phoenix

UPDATE

Updated 00Z Aviation Discussion.

KEY MESSAGES

- Temperatures near to slightly below normal today will warm back above normal this weekend, with widespread lower desert highs in the middle nineties by Sunday.

- Breezy winds through the rest of today, along the Colorado River Valley, and tomorrow morning, followed by a strong easterly gradient wind developing across south-central Arizona Sunday morning.

SHORT TERM /TODAY THROUGH SUNDAY/

A trough that passed by to the north this morning, and is now seen moving across the Rockies, helped push a dry cold front down the Lower Colorado River. A strong pressure gradient across the same area, driven by a surface high in the Great Basin, has led to strong northerly winds down the river. Wind gusts have subsided from earlier this morning and the Wind Advisory for the area was allowed to expire at 1300MST/PDT. The Blythe Airport measured a peak wind gust of 60 mph this morning, the highest in the area, but gusts are now down to around 25-35 mph along the river and across higher elevation parts of SE CA. Winds should continue to slowly subside through the rest of the afternoon, but remain breezy through the evening. Winds are notably lighter across south-central AZ.

The passing trough also helped cool temperatures down slightly, with midday temperatures running 2-5F cooler than the same time yesterday. This will result in afternoon highs right at to a couple degrees below daily normals, with lower desert communities topping out in the low to mid 80s.

Heading into the weekend, shortwave ridging will follow the departing trough, which means no threat for precipitation. Height rises will translate to a rapid warming of temperatures, with the latest NBM forecast supporting high temperatures Saturday at around 5 degrees above normal and then up to 10 degrees above normal for Sunday, with highs in the mid 90s. Morning low temperatures will remain seasonally cool through Saturday morning, but lows will also warm several degrees above normal on Sunday. An increase in easterly winds across southern AZ Saturday night/Sunday morning may also keep morning temperatures warmer than currently forecast. The surface high in the Great Basin now will strengthen and spread across the Rockies and into the Southern Plains Saturday into Sunday. This progression will initially lead to some breezy NE winds Saturday morning across parts of central AZ and then a stronger easterly gradient winds Sunday morning with the high in the Plains. Hi-res and global models are highlighting an abnormally strong easterly wind Sunday morning, with mountain and ridgetop wind gusts pushing 40-50 mph east of Phoenix. The breezy easterlies should mix to the surface across south-central AZ after sunrise, but with gusts mostly peaking in the 20-30 mph range.

LONG TERM /MONDAY THROUGH FRIDAY/

Early next week, the upper level pattern with West-Central CONUS ridging and a broad upper low off the West Coast will be maintained, however, shortwaves rotating around the broad upper low to our northwest will bring sensible weather changes for the forecast area as we head into the middle of the week. Forecast uncertainty remains moderate to high, with WPC cluster analysis revealing discrepancies in timing and the N/S displacement of the upper low as it eventually makes its way inland. The uncertainty is still reflected in the probabilistic NBM temperatures, as IQRs for the forecast highs/lows increase to 5F or greater Wednesday onward. Overall, temperatures should retreat closer to or even slightly below seasonal normals during the middle of next week. Another uncertainty is whether the forcing from the shortwaves rotating about the broad upper low will combine with meager moisture (mostly in the mid levels) to produce light shower activity over portions of AZ. However, the vast majority of global guidance shows the area remaining dry, with PoPs below 10%. Regardless, this pattern evolution will almost certainly result in another widespread breezy to locally windy period during the middle of the upcoming work week.

AVIATION

Updated at 0020Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

No major aviation concerns throughout the TAF period. Winds will follow typical diurnal tendencies with a later than usual easterly shift tonight, but one similar to last night (~09-10Z). Wind speeds will mostly aob 10kts. However, late tomorrow morning gusts between 15-20kts are possible between 16-18Z. Otherwise, mostly clear skies will continue through the period.

Southeast California/Southwest Arizona including KIPL and KBLH:

No major aviation concerns throughout the TAF period. At KIPL, winds will be aob 8 kt through the period and favor a W/N direction through the period. At KBLH, gusts up around 20 kt will continue over the next couple of hours before subsiding. Then, wind speeds will generally be aob 10 kt through the remainder of the period. Winds will favor a N/NW direction through the period. Skies will remain mostly clear through the period, with FEW high clouds starting to filter in at the end of the period.

FIRE WEATHER

Elevated fire weather conditions are ongoing along the Lower Colorado River Valley and parts of Southeast CA, where very dry air is combining with breezy northerly winds. The winds have at least subsided from this morning, but will remain breezy through this evening. Dry and occasionally breezy conditions will then follow most days through the next week. Winds will be much lighter, generally below 15 mph, on Saturday, and then a strong easterly wind will develop across south-central AZ Sunday morning, but given the time of day RH values will be above critical levels. Still, some locally elevated fire weather conditions may exist across south-central AZ midday through early afternoon Sunday. Afternoon MinRHs below 15% and at times in the single digits will be common through the next 7 days, with minor day to day variations. Overnight recoveries will offer little relief this weekend, with values commonly between 10-30% (on the lower end of that range for the western deserts).

PSR WATCHES/WARNINGS/ADVISORIES

AZ...None. CA...None.