textproduct: NWS Phoenix

UPDATE...Updated 18Z Aviation Discussion

KEY MESSAGES

- Regional temperatures will continue their gradual warming trend through the week, with highs likely reaching near 80 degrees by the weekend.

- Persistent high pressure will translate to dry and tranquil conditions through at least the first few days of February.

SHORT TERM /TODAY THROUGH THURSDAY/

Current objective analysis reveals high amplitude ridging centered over the Great Basin and up through the Canadian Rockies, promoting quiet conditions for a good portion of the western CONUS. As for the Desert Southwest, dry weather with warming temperatures will be main story through the next few days. Global models do point towards a Pacific trough moving onshore before eventually diving through the Intermountain West during mid-week. While the trajectory of this system will be too far to north to bring any significant changes, the tightening of the regional pressure gradient will likely generate breezy conditions, particularly around the Lower Colorado River Valley and high terrain east of the Phoenix metro. This wave will also suppress 500mb height rises during the Wednesday-Thursday timeframe, likely causing a brief pause in day-to-day temperature increases, especially for areas east of the Colorado River that will be in closer proximity to the low. The thermal pause will be brief as this disturbance ejects to the Plains by Thursday allowing for the resumption of increasing heights aloft. Temperatures this afternoon for the lower deserts will be near normal in the upper 60s to lower 70s, increasing to the lower and middle 70s by Thursday.

LONG TERM /THURSDAY THROUGH TUESDAY/

The upper-lvl pattern will not change much through the end of the workweek as our forecast area remains between ridging over the West Coast and troughing over the midwest. A series of shortwave troughs will progress through the Intermountain West late this week. However, these shortwaves will have little to no affect on our weather aside from bringing breezy conditions to the Lower Colorado River Valley Thursday and Friday. As ridging aloft continues to build over the West Coast, temperatures will warm a couple degrees each consecutive day with highs across the lower deserts pushing into the mid 70s by the end of the week.

Ensemble members remain in agreement that the ridge of high pressure over the West Coast will gradually shift eastward, resulting in 500 mb hghts rising to around 580-582 dam over the Desert Southwest Saturday and Sunday. This will result in a return of well above normal temperatures (8 to 10 degrees above normal). Latest NBM deterministic guidance shows highs reaching well into the upper 70s and even a few 80 degree readings across the lower deserts this weekend. It does look like the ridge will finally shift east of our region early next week and be replaced with shortwave troughing. As this occurs, we could see temperatures dip by a few degrees Monday and Tuesday. For now the forecast will remain dry through at least the first half of next week.

AVIATION

Updated at 1730Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation weather concerns expected throughout the TAF period. Winds will generally be light and diurnal with speeds aob 7 kts along with extended periods of variable to calm conditions. Clear skies will prevail through this afternoon before high cirrus decks move in by this evening.

Southeast California/Southwest Arizona including KIPL and KBLH: No aviation weather concerns expected throughout the TAF period. Winds will generally exhibit a west to north component with speeds aob 7 kts along with extended periods of variable to calm conditions. Clear skies will give way to increasing high cirrus decks by late this afternoon/early this evening.

FIRE WEATHER

Dry weather and above normal temperatures will prevail through the remainder of this week and into this weekend. Afternoon minimum humidity values will range from 10-25% across all districts with overnight recoveries ranging from fair to poor around 35-55%. Elevated easterly winds winds are expected again this morning across the higher terrain areas of southcentral AZ where gusts up to 20-25 mph will be possible. Winds will become lighter this afternoon and follow typical diurnal patterns. There could be some breeziness across the Lower Colorado River Valley Thursday and Friday, otherwise wind speeds should remain less than 15 mph.

PSR WATCHES/WARNINGS/ADVISORIES

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