textproduct: NWS Phoenix

UPDATE

Updated Aviation

KEY MESSAGES

- Slightly above normal temperatures with areas of moderate HeatRisk will prevail throughout the week before retreating closer to normal over the weekend.

- Other than a slight chance of a thunderstorm in eastern Arizona during the middle of the week, dry conditions under mostly sunny skies will prevail the next several days.

- Locally breezy conditions will develop late in the week, particularly across the lower Colorado River valley and higher terrain communities.

SHORT TERM /Today through Thursday/

Omega blocking continues across the northern Conus, however this pattern will be dislodged and realigned over the next 72 hours due to stronger progressive wave energy entering the Pacific NW. Meanwhile, an enhanced subtropical jet persists over the SW Conus in this split flow regime with deeper northern stream waves beginning to influence the progression further south. The preponderance of modeling continues to push a notable southern stream vorticity center farther south into Mexico leaving the forecast area under weaker flow and higher heights than previously forecast. As a result, H5 heights will increase closer to a 585-587dm range during the middle of the week yielding high temperatures solidly 5F or more above normal. This tips more of the CWA just into a moderate HeatRisk category during the middle of the week, however well short of records and not terribly unusual for early June.

Despite the southern stream vorticity center diving well south into Mexico midweek, the forecast area will fall into a favorable divergence pattern aloft with marginally decent ascent mechanisms. Confidence is good that thunderstorms materializing across New Mexico during the middle of the week will send westward propagating outflow boundaries into far eastern Arizona improving overall moisture profiles. Consequently, isolated thunderstorms become more likely near the White Mountains Wednesday and Thursday afternoon, potentially leaking into far eastern Gila County. Rather than any impacts from rainfall, the greater threat will be lightning strikes with little rainfall capable of sparking wildfires in dry late spring fuels.

LONG TERM /Friday through Monday/

Through the weekend, the full suite of ensemble members are in fair agreement depicting the northern Mexico shortwave slowly ejecting into the southern plains with some measure of ridging holding over the Southwest ahead of deeper negative height anomalies approaching the West coast. The trend among the majority of ensemble membership is towards a slower progression of this troughing across the East Pacific resulting in less local influence of height falls as the southern extent of wave lags the Southwest before lifting into the Great Basin. As a result, H5 heights may only decrease modestly over the weekend into a 582-585dm range and temperatures only cooling near the seasonal average. Numerical spread remains quite large during this time frame reducing forecast confidence with respect to temperatures. However, this pattern evolution will force an increased low level pressure gradient with afternoon/evening wind gusts becoming more pronounced and heightening the potential fire danger. Forecast confidence deteriorates further during the beginning of next week tied to the exact evolution of troughing entering the western Conus, but there are a growing number of ensemble members suggesting more predominant ridging and warming versus previous iterations.

AVIATION

Updated at 1100Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns are expected during the TAF period. Winds will follow diurnal trends with some occasional gusts in the mid to upper teens during the afternoon hours. Other than some exiting high clouds this morning and distant high terrain CU later, skies will be mostly clear through Wednesday morning.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are expected during the next 24 hours. Outside of some periods of VRB to calm conditions, mainly during the the remainder of the morning hours, winds will follow familiar diurnal trends with speeds generally aob 12 kt. Skies will be mostly clear through Wednesday morning.

FIRE WEATHER

The threat for a few lightning strikes with little rainfall in far eastern Gila County Wednesday and Thursday is the main fire weather hazard this week. With temperatures hovering several degrees above normal, winds will maintain a diurnal upslope/nocturnal drainage pattern. However, gusts will increase markedly towards the end of the week, particularly across the lower Colorado River valley and mountainous locations of eastern districts. This will result in periods of an elevated to near critical fire danger during the afternoon/evening, especially over the weekend. Minimum afternoon humidity levels will generally fall in a 5-15% range following a wide ranging poor to fair overnight recovery of 15-45%.

PSR WATCHES/WARNINGS/ADVISORIES

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