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 shower or thunderstorm in eastern Arizona during the next few afternoons, dry conditions under mostly sunny skies will prevail through the weekend.

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

SHORT TERM /Today through Friday/

Current objective analysis reveals a fairly complex pattern over CONUS with an omega block beginning to break down over the northern tier of the county, while a weak Pacific low meanders close to the Baja Peninsula. The latter of these features will continue on southeastward progression, eventually settling over Chihuahua, Mexico by the end of the workweek. During this progression, our regional height field will not change much, hovering around 586- 587dam through Friday, slightly above normal for the start of June. This will translate to surface temperatures also running a few degrees (4-6F) above normal with lower desert highs running between 103-109 degrees through Friday. Although not completely abnormal, these temperatures will still result in widespread moderate HeatRisk, posing a risk to those sensitive to the heat and others who may not have ways of sufficiently cooling or hydrating themselves.

The only noticeable deviation from hot and calm conditions through the next few days will come in the form of some very isolated showers and thunderstorms over far eastern Gila County this afternoon and again Thursday, and some breezy conditions developing around the Lower Colorado River Valley and higher terrain areas. toward the end of the week. The slightly increased rainfall potential is the result of some modest moisture advection working its way westward from convective activity that spawned over central and eastern New Mexico. PWAT anomalies may actually push north of 150- 200% as far west as eastern Maricopa and Pinal Counties, but given that June is climatologically our driest month, it does not take much moisture to inflate those values. The best moisture will be focused over the White Mountains, along with other enhanced terrain features in Graham and Greenlee Counties. However, it is not out of the question that convection over these area pushes an outflow toward our area of Gila County and sparks some isolated showers or thunderstorms, though chances are slim around 10-20%. As for the winds, models have an eastern Pacific ridge interacting with the previously mentioned northern Mexico low, subtly enhancing our regional pressure gradient. By Thursday, gusts 20-25 mph will be most common for areas mentioned above, increase to 25-30 mph by Friday. With RH values running around 10% and below, even this marginal breeziness will result in elevated fire danger.

LONG TERM /Saturday through Tuesday/

As we head into the weekend, ensembles point towards another trough moving over western portions of the CONUS, which will eventually become more amplified and stretch from British Columbia down the California coast. However, uncertainty remains regarding the strength and positions of this potential disturbance. The increasing temperature spread through the weekend and into the start of next week between the NBM 25th and 75th percentile reflects this uncertainty. Nonetheless, even with the cooler air associated with this potential system, it appears widespread triple digits are here to stay. Regardless of which ensemble solution comes to fruition, the continuation of breezy, to perhaps locally windy conditions appears likely. The main question will be how strong gusts may become, which will be dependent on how tight the regional pressure gradient becomes. With little moisture flux, any breeziness will keep the fire weather risk elevated at least through Sunday.

Forecast confidence does not improve for the start of next week as model clusters show a wide variety of outcomes, with some showing continued troughing, while others favor the return of high pressure. The return of ridging across the western CONUS appear to be most likely outcome at this time, but how amplified this feature becomes, its placement, and if we remain under some influence of a lingering area of low pressure remains uncertain at this time. One thing that does appear certain though, other than our high terrain rain chances today and Thursday, dry conditions are likely to prevail over the next week at least for most of the region.

AVIATION

Updated at 1120Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and Southeast California/Southwest Arizona including KIPL and KBLH:

No significant weather issues will exist through Thursday morning under passing cirrus decks and a few afternoon CU/CB developing over mountains east of Phoenix. Confidence is very good that trends in wind speeds and timing of directional shifts will be very similar to the past 24 hours. However, the late evening/overnight shift back to an easterly direction around the Phoenix metro may occur a few hours earlier than the past couple days due to decaying outflow descending into the valley from storms over mountains.

FIRE WEATHER

The threat for a isolated dry thunderstorms over southern Gila County today and Thursday is the main fire weather hazard over the next few days. Winds will follow typical diurnal tendencies with typical afternoon upslope breeziness the next couple of afternoons. Gusts begin to pick up Friday and into the weekend, mainly across the Lower Colorado River Valley and high terrain areas of the eastern districts. With daily MinRHs hovering close to 5-10%, even marginal breezes will result in periods of elevated fire weather conditions. Isolated instances of near critical to critical conditions cannot be ruled out. Overnight recovery will offer very little in terms of relief as MaxRHs run between only 15-45% for most areas. Breezy, to locally windy, conditions are likely to continue into the weekend, potentially lingering into the start of next week, resulting in a prolonged period of daily occurrences of elevated to near critical fire weather conditions starting on Friday.

PSR WATCHES/WARNINGS/ADVISORIES

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