textproduct: NWS Phoenix

UPDATE

00Z Aviation Discussion

KEY MESSAGES

- Slightly above normal temperatures will persist through Friday before readings warm again this weekend returning to around 10 degrees above normal.

- Increasingly gusty north winds will impact locations through the lower Colorado River valley Friday morning with localized blowing dust possible. - There is a chance of a few showers and thunderstorms early next week across the eastern Arizona high terrain.

SHORT TERM /Today through Saturday/

Broad troughing continues over the western Conus with negative height anomalies progressing through the northern Rockies and upstream ridging amplifying into the Pacific NW. Weakly cyclonic flow persists over the CWA with H5 heights in the trough base not far from 576dm ensuring temperatures hover slightly above normal and near a persistence forecast through tomorrow. The introduction of sharp ridging entering the NW Conus will promote nocturnal low level pressure rises over the Great Basin, tightening the pressure gradient and inducing a northerly LLJ surging down the Colorado River valley. Ensemble mean forecasts suggest H9-H8 winds peaking 30- 40kt around sunrise with partial mixing to the surface before weakening by late morning/early afternoon. HREF members appear somewhat overzealous in mixing higher momentum to the surface during a non-favorable time of day, however a brief burst of advisory level wind gusts will be possible across a few population centers and transportation corridors just after sunrise. Otherwise, the strongest winds should be reserved for ridgetop locations before weakening with the relaxation of H9-H8 wind speeds through the day. Very minor height rises will spread into the region Saturday marking the beginning of another warming trend heading into next week as the regional pressure gradient relaxes while drier air

LONG TERM /Sunday through Wednesday/

A mostly quiet weather pattern is expected through the first half of next week as an eastern Pacific ridge moves into the Western U.S. This will help to quickly boost temperatures with highs topping into the low to mid 90s on Sunday. Models have also been trending toward a weak shortwave trough tracking across northwest Mexico and southern Arizona on Sunday, while the flow in the lower levels turns out of the southeast. Model consensus as of now shows a brief 12-24 hour period on Sunday of moist southeasterly flow into Arizona, potentially raising low level mixing ratios to between 6-7 g/kg across the eastern Arizona high terrain. If this moisture does make its way into eastern Arizona by the afternoon hours, some convection is likely to develop. The latest NBM shows this potential with PoPs now as high as 30-40% across eastern Gila County. The drier conditions into the lower deserts will most certainly prohibit any convection getting close to the Phoenix area.

By Monday, moisture should begin to decrease again likely ending any rain chances across the area. Upper level ridging will still be in charge over much of the Western U.S. going into the middle of next week and this should keep our region under overall dry conditions with temperatures staying stable in the low to mid 90s.

AVIATION

Updated at 2300Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns are expected during the TAF period. Other than a few lingering gusts upwards of 20 kts this evening, winds should follow light and diurnal trends, with the usual morning E'rly shift taking place later than usual. Outside of a break in the clouds tonight into Friday morning, SCT-BKN high bases will be common during much of the daylight hours.

Southeast California/Southwest Arizona including KIPL and KBLH: The main aviation concern over the next 24 hours will be breezy to windy conditions at both terminals. The strongest gusts are likely to be focused at KBLH where readings will near 30 kt. Given these enhanced winds and the prevailing direction being from the north,reduced VIS in blowing dust cannot be ruled out, but confidence is too low to include mention BLDU in the TAF at this time. At KIPL, peak gusts out of the west between 20-25 kt will be more common. Clearing skies this evening will give way to increasing high base coverage by Friday morning.

FIRE WEATHER

Dry weather returns to the region with temperatures hovering slightly above normal through Friday. Minimum humidity levels will fall into a 15-25% range today with even drier values closer to 10% Friday. Fair to good overnight recovery of 40-70% will deteriorate into a poor to fair 20-50% range. Enhanced wind gusts 30-40 mph will be possible in western districts on Friday creating elevated fire weather conditions, while other areas will only see modest afternoon breeziness. Lighter winds and temperatures rising to well above normal are then anticipated for the weekend. Moisture is expected to briefly increase across eastern Arizona this weekend potentially bringing chances for showers and thunderstorms across the higher terrain on Sunday.

PSR WATCHES/WARNINGS/ADVISORIES

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