textproduct: NWS Phoenix

KEY MESSAGES

- Wind advisories continue across portions of the region through this morning with gusts occasionally over 35 mph resulting in areas of blowing dust and difficult travel for high profile vehicles.

- A slight chance of light rain will arrive into parts of south- central Arizona over the weekend with the better chances focused over higher terrain locations. - A Pacific low pressure system moving into the Southwest during the middle of next week will lead to much better rainfall chances with the possibility of a few embedded thunderstorms, as well as cooler temperatures

SHORT TERM /Today through Sunday/

A defined Rex block can be seen on both GOES WV imagery and RAP-40 500mb analysis. The core of the high is currently over Rockies and the core of the cut off low remains positioned over the northern coast line of the Baja Peninsula. The high pressure will continue to push eastwards into the northern Plains throughout the afternoon today and the pressure gradient that brought wide spread windy conditions across the region will begin to weaken. Until then lingering strong gusts will linger throughout the morning hours today, with potential for areas of lofted dust. Thats said a Wind Advisory remains in effect until 11 AM MST for most of Pinal County and the higher terrain east of Phoenix of southern Gila County, where gusts between 40-55 mph will be possible, especially along the mountain peaks. Afterwards the combined effect of a weakening pressure gradient with an increase in thicker cloud coverage as the cut off low opens open through the region will lead to less mixing and therefore cutting winds down below advisory level leading into the afternoon.

As mentioned previously the Rex block is expected to open by tonight and drift through the region over the weekend. This is expected to advect a decent amount of mid to high level moisture into the region with PWATs forecasted to rise near to slightly above 1" over the weekend. While this amount of moisture is between 150-200% of normal, the lower levels are expected to remain quite dry restricting much rainfall from reaching the surface in most areas. However, PoPs between 20-35% remains in the forecast for today- Sunday across south-central and the higher terrain areas east of Phoenix. By late Sunday afternoon PoPs reduce to below 10% CWA wide as the open wave trough lifts into Northern Arizona.

LONG TERM /Monday through Thursday/

By early next week next week the high pressure will be well over NE CONUS and the open wave trough will begin to be absorbed into the mean SW flow head of the next incoming low pressure system diving down the western coastline. Another low chance (20-30%) of showers manifest Monday morning across the higher terrain, however yet again, if anything does develop total accumulations are expected to be near zero. By Tuesday, deep troughing and strong negative height anomalies will amplify and intensify along the west coast, however confidence is exact the timing and depth of this feature remains low to moderate. The ECMWF deterministic is forecasting a slower and more robust rainfall scenario, while the GFS deterministic provides a faster and more mild rainfall potential. Regardless, the timing of any rainfall potential is highlighting Wednesday and Thursday. Additionally, with the uncertainty of this next system a wide spread in NBM temperatures have presented themselves throughout the week, though below normal highs are likely.

AVIATION

Updated at 0545Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Main aviation concerns will be continued breeziness and lingering slantwise VIS reduction due to lofted dust. Winds through sunrise will behave similar to the previous night with relatively elevated sustained speeds around 10-15 kt and sporadic gusts upwards of 25 kt or so. KSDL will be more susceptible to these gusts due to their closer proximity to terrain features and orientation of the overall flow. Though not included in the TAFs, localized LLWS could create operational impacts overnight due to winds 35-45 kt a few thousand feet above the surface. More persistent breeziness will reemerge after sunrise before a noticeable downtrend in speeds take place during the back-half of the forecast window. Slantwise VIS should begin to improve in conjunction with the weakening winds. Considerable cloud cover will be present over the region, with bases dropping to 9-12 kft by Saturday afternoon.

The thick cloud cover will be accompanied by isolated shower chances starting Saturday afternoon and evening and VCSH has been added to each of the TAFs from about 00Z to the end of the forecast. However, confidence in this timing is low, and it is not out of the question that shower activity moves in a few hours sooner. With that being said, mention of -SHRA has been excluded from the TAFs as operational impacts will be minimal at best with potential activity. TEMPOs that include the mention of rainfall may be added in subsequent forecasts if confidence increases or greater impacts are expected.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected during the next 24 hours. Outside of periods of VRB conditions, NE'rly flow will be favored at both terminals through much of the forecast. Isolated gusts upwards of 25 kt cannot be ruled out at KBLH through sunrise. Isolated SHRA will be seen over the region tonight, with some moving within the vicinity of KIPL. However, no impacts are expected with this activity. Considerable cloud cover will be present through Saturday afternoon, with the lowest bases around 9-12 kft.

FIRE WEATHER

Strong east winds will continue through this morning across southern Arizona with the most pronounced gusts over mountain tops of eastern districts. Gusts 40-45 mph may be common over these locations with a portion of these winds building into lower elevations by late morning, before weakening heading into the afternoon hours, with even weaker winds Sunday through the middle of next week. Light showers are possible this weekend, and particularly over eastern districts, but the chance for wetting rain is low (~10%). The strong east winds will result in minimum humidity levels 15-30% today, but increasing closer to a 30-50% range thereafter. Overnight recovery should be good to excellent. A Pacific weather disturbance will bring increased chances of wetting rainfall, breezy winds, and cooler temperatures during the latter half of next week.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Wind Advisory until 11 AM MST Saturday for AZZ547-552-553-555- 557-558-560>562.

CA...None.