textproduct: NWS Phoenix

KEY MESSAGES

- Breezy conditions and locally elevated fire danger will exist today, with the strongest gusts focused over the eastern Arizona high terrain.

- Lighter, more seasonable wind speeds with only modest afternoon breezes will return this weekend and likely persist through much of next week.

- Temperatures as much as 10 to 15 degrees below normal today will quickly warm over the weekend, reaching a slightly above normal category early next week.

SHORT TERM /TODAY THROUGH SUNDAY/

Early afternoon water vapor satellite imagery and 500 mb RAP analysis depict an upper level low, one which has been cut off and meandering over CA/NV for much of the week, opening up to the northern stream and finally ejecting northeastward towards the Four Corners. Relatively strong midlevel flow with NAEFS mean 700 mb wind speeds upwards of 30-35 kts (above the 90th percentile of climatology) remains over AZ, tracking ahead/around the base of the upper low. By late afternoon, this narrow band of higher momentum air will have shifted almost entirely east of the forecast area. Mixing heights remaining below the 700 mb level, as shown in GFS bufr soundings for Phoenix, will preclude chances for this higher momentum air to mix down to the surface, even during peak heating. However, gusts up to these speeds (30-35 kts) may be realized over the Northeastern AZ higher terrain. For our forecast area, the strongest gusts (around 30 mph) will be relegated to the higher terrain of Southern Gila County, resulting in locally elevated fire danger.

The main story through the weekend will be warming temperatures and a return to more seasonable, lighter winds Saturday onward. A period of quasi-zonal flow establishing over the weekend, with H5 heights rebounding to the 50th-60th percentile of climatology for late May/early June (582-584 dam), is favored by ensemble membership. Narrow spread in latest probabilistic NBM guidance suggests excellent confidence in temperatures heating back up to near the daily normals by Sunday. Forecast highs for the lower deserts this afternoon mostly in the middle 80s represents values as much as 10 to 15 degrees below daily normals. By Saturday, lower desert highs are likely to reach the lower 90s, followed by further warming into the upper 90s to near 100F Sunday.

LONG TERM /MONDAY THROUGH THURSDAY/

Upper level ridging will begin to settle over the Desert SW starting Monday. Latest model guidance has shifted the axis of this ridge more eastward, now centered over the eastern half of Texas, where previous runs had the axis centered more over central to western Texas. Regardless of the ridge axis position, H5 heights over Arizona will increase to 585-588 dam causing temperatures to warm to 103F-108F starting as early as Monday and lasting through the week. These temperatures will easily push our HeatRisk into a moderate category, but relatively mild overnight lows in the upper 60s to mid 70s will help to limit the chance of reaching near the major category. Otherwise, dry conditions with mostly clear skies through early next week.

AVIATION

Updated at 1720Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: Winds will be the primary weather issue through Saturday morning under mostly clear skies. Westerly winds will continue through the evening and into the overnight hours. Some occasional 15-20kt gusts are expected mid/late afternoon. A more defined easterly switch should occur late this evening/overnight. Winds will then go back westerly late tomorrow morning.

Southeast California/Southwest Arizona including KIPL and KBLH: No major weather issues will exist through Saturday morning under clear skies. Winds will generally maintain a westerly component at KIPL while oscillating between SW and NW at KBLH. Sustained speeds around 10kt will be common with some occasional afternoon/early evening gustiness, though far weaker than experienced the past few days.

FIRE WEATHER

Locally elevated fire weather conditions will exist over the eastern districts this afternoon into the early evening due to elevated wind speeds, with gusts peaking between 25-35 mph over the higher terrain. This weekend into early next week, lighter winds following mostly diurnal upslope/upvalley and nocturnal drainage patterns will prevail, with typical afternoon breeziness for late May/early June. Below normal temperatures today will quickly warm to near normal Sunday and slightly above normal early next week. Afternoon minRHs will decrease from 15-25% today to a 10-20% range areawide Saturday, then further decrease to an 8-15% range Sunday. Afternoon minRHs will commonly bottom out in the single digits areawide early next week. Overnight will similarly deteriorate over the weekend, with values between 35-60% tonight decreasing into a 25-45% range Saturday night. Poor overnight recoveries will be common early next week.

PSR WATCHES/WARNINGS/ADVISORIES

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