textproduct: NWS Phoenix

UPDATE

Updated Aviation Discussion.

KEY MESSAGES

- Another weather system will clip the area today resulting in widespread gusty winds and increased precipitation chances over the Arizona high terrain.

- A quick moving system Thursday night into Friday will reinforce cooler temperatures with additional chances for light showers across central Arizona.

- Drier weather with much warmer temperatures will return to the region by early next week.

SHORT TERM /TODAY THROUGH FRIDAY/

A deep upper level low continues to drive southeastward along the West Coast with the base of the trough now entering central California. The trough is helping to drive impressively strong winds aloft with near record winds within a deep H8-H2 layer across southern California into portions of the Desert Southwest. This strong gradient across the Southwestern U.S. has started to result in windy conditions across southern California with gusts already reaching 45 mph in some parts of southeast California. Strong winds with gusts of 40-50 mph will be possible across southeast California through early afternoon with windy conditions and gusts of 35-45 mph developing across portions of southern and central Arizona by mid morning. Wind Advisories remain in effect for all of southeast California and southwestern Arizona through mid afternoon. Patchy blowing dust will also be possible through early afternoon, particularly across southeast California.

The main shortwave is currently tracking across central California and is slated to turn to the east later this morning tracking across northern Arizona and southern Utah. Modest system moisture is providing good precipitation across the California coast, but much of the moisture will be lost as it tracks across the interior mountains today. Guidance does show a swath of mid-level moisture advecting southeastward through the area today along an advancing cold front and this should help to drive a period of decent snow across the Arizona high country and scattered rain showers across the foothills and higher terrain just to the north and east of the Phoenix area. The quick moving nature of the shortwave and meager moisture is expected to only bring rainfall amounts of maybe a few hundredths of an inch into northern portions of the Phoenix area to up to 0.25" across the higher terrain. Snow levels during the peak of the shower activity will mostly around 6000 feet but lowering into the evening to as low as 4500-5000 feet as showers are diminishing. This could result in some rain changing over to snow this evening across portions of eastern Gila County, but no accumulations are expected.

Much cooler temperatures will also be realized starting today with morning temperatures starting out in the mid to upper 40s in some areas. As temperatures rise into the 50s by mid to late morning, the breezy to windy conditions should make it feel even colder. Forecast highs for today are now even lower than yesterday's forecast with most lower desert locations only reaching into the upper 50s to lower 60s this afternoon. Overnight lows tonight should also get quite chilly as we should lose most of our clouds. Some areas should still have some breeziness overnight limiting the cooling, but more sheltered areas may easily dip into the 30s.

Thursday into Friday will bring yet another disturbance tracking out of the northwest creating another breezy to locally windy day on Thursday, but advisory levels are much less likely compared to today. Shortwave energy from this system should take very similar track just to our north resulting in more snow for the Arizona high country later Thursday through Friday morning along with a chance of some showers skirting by just to the north and northeast of Phoenix. High temperatures will basically be stable with the passage of this system with lower desert highs mostly in the lower 60s. Overnight lows will also stay below normal with Friday night and Saturday morning likely being the coldest night this week as readings dip into the mid to upper 30s over the majority of the lower deserts.

LONG TERM /SATURDAY THROUGH TUESDAY/

Much quieter weather will move in starting Saturday as upper level ridging overtakes the region after the Friday system exits to the east. The cold air mass will mostly stay around for Saturday as highs only warm back to around 70 degrees, but the warming trend will pick up speed going into early next week. Guidance shows H5 heights rising enough to breach the 90th percentile of climatology Monday into Tuesday before gradually lowering through the middle of next week. The latest NBM forecast highs show lower desert readings easily topping 80 degrees starting Monday with some potential for the warmest locations to reach 85 degrees during the first half of next week. However, there will likely also be a decent amount of higher level clouds next week as an atmospheric river is expected to just miss our region to the northwest. Higher clouds spilling into the ridge may at times limit daytime highs depending on the thickness of the clouds.

AVIATION

Updated at 1130Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Gusty southwest winds along with a period of VFR CIGs near 6 kft AGL will be the main aviation concerns, particularly during the late morning/afternoon hours. Breeziness will begin to pick up after sunrise, with peak gusts near 25 kts during the early afternoon hours. Some occasional higher gusts closer to 30 kts will be possible in conjunction with a frontal passage. SHRA activity will develop mainly north of the Phoenix airspace as coverage of lower cloud decks increases later this morning, and so VCSH has been included at KDVT and KSDL, however, confidence is too low to include direct SHRA impacts at any of the terminals.

Southeast California/Southwest Arizona including KIPL and KBLH: Strong, gusty westerly winds will be the main aviation concern during the next 24 hours. The amount of decoupling over the next several hours remains a difficult aspect of the forecast, leading to low confidence in wind speeds and whether gusts will be observed through the next several hours. Marginal LLWS impacts may be observed, but should remain below TAF thresholds. Gusts will become more persistent after sunrise, gusting to around 25 kts at KBLH, while KIPL will see gusts closer to 30 kts. Although confidence is low, reduced VIS due to blowing dust, mainly at KIPL, cannot be ruled out during the latter portion of the forecast. Besides a brief window of SCT to perhaps BKN low decks near 4-6k ft in association with a frontal passage late this morning, skies will be generally clear.

FIRE WEATHER

Wind speeds will increase again today, particularly across western districts with gusts 30-40 mph common. A few showers will be possible in foothill and mountain locations mainly this afternoon, however instances of wetting rainfall will be isolated before clearing Thursday with weaker winds. Minimum humidity values will range widely between 25-60% this afternoon, then tighten to 25-45% Thursday. This will follow good to excellent overnight recovery of 60-100%. Drying and warming conditions are expected for the weekend with MinRHs dropping into the teens for the lower deserts and temperatures rising to above normal.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Wind Advisory from 8 AM this morning to 4 PM MST this afternoon for AZZ530>533-535-536.

CA...Wind Advisory from 7 AM this morning to 3 PM PST this afternoon for CAZ565-567.

Wind Advisory until 3 PM PST this afternoon for CAZ560>564-566- 568>570.