textproduct: NWS Phoenix

UPDATE

Updated 12Z Aviation Discussion.

KEY MESSAGES

- Freeze Warnings are in effect this morning across the typically prone rural and low lying areas.

- Breezy to locally windy conditions are expected across the higher terrain east of Phoenix tomorrow morning and afternoon.

- Below normal temperatures continue today, warming near to slightly above normal Sunday, with gradually warming through the majority of next week.

- Dry conditions will prevail across the region through at least the next week.

SHORT TERM /TODAY THROUGH SUNDAY/

500 mb RAP analysis show a longwave trough stretching from the Plains all the way back down into the Baja along with ridging building in over coastal western CONUS. Our region remains under a dry, cold air mass with PWATs around 0.1-0.2". Water vapor satellite imagery shows the dry air mass overhead along with dry northerly flow continuing over our region. Nighttime microphysics satellite imagery shows clear skies over our region. This in combination with fairly light winds (generally in the 5-10 mph range) will allow us to maximize radiational cooling this morning. This will result in another chilly morning, the coldest one of the winter season so far. Temperatures are already around 5 degrees cooler than they were at this time yesterday morning across much of the region. Temperatures are forecasted to bottom out this morning in the upper 20s to low 30s across the typical, cold prone, rural and low-lying areas. Elsewhere, in the more urban areas temperatures are forecasted to bottom out around the mid 30s to low 40s this morning. With high pressure building back in over western CONUS, this has allowed for heights aloft to rise, which will cause temperatures this afternoon to be a few degrees warmer than they were yesterday, however still slightly below normal. Afternoon high temperatures today are forecasted to be in the low to mid 60s across the lower deserts and in the 50s across the higher terrain.

Further warming is expected tomorrow, with both the morning lows and afternoon high temperatures. Despite the warming temperatures, some sheltered, rural, low-lying areas still may reach or near the freezing mark Sunday morning. So make sure to keep protecting the 4 P's (people, pet, pipes, and plants), especially if you live in those typical cold prone locations. Afternoon high temperatures are forecasted to go back to near to slightly above normal on Sunday. The lower deserts are forecasted to see highs in the upper 60s to near 70 degrees and the higher terrain areas are forecasted to see high temperatures ranging from the mid 50s to low 60s.

A piece of energy is expected to break off the aforementioned trough late tonight into tomorrow and form a closed low over the Baja. At the same time, the ridge will continue to build just north of this low, resulting in a Rex blocking pattern. This rex blocking pattern is expected to hold into the first part of next week. This pattern will result in a prolonged period of easterly winds due to an easterly jet forming over the Desert Southwest, in between the low and high pressure systems. This will result in some periods of enhanced winds over the region this weekend. Models show this jet maximizing over our region Sunday morning and afternoon. This is when we are expecting the strongest winds, particularly over the higher terrain to the east of Phoenix, where winds in excess of 40 mph are possible, especially along ridgetops. Due to this a Wind Advisory will likely need to be issued. Despite this closed low influencing our region, it will not bring any precipitation chances to our region as the abundance of dry air will remain in place.

LONG TERM /MONDAY THROUGH FRIDAY/

Ensemble members are in good agreement that the rex blocking pattern will hold through at least the beginning of the upcoming workweek before the low finally breaks down during the latter half of the week. At the same time, the high pressure will maximize during this time, which is when we're forecasting the warmest temperatures of the upcoming week. Gradually warming temperatures are expected through the week. Afternoon high temperatures Monday and Tuesday are forecasted to be in the low to mid 70s across the lower deserts and in the 60s across the higher terrain. Then for the latter half of the week high temperatures warm into the mid to upper 70s to near 80 degrees across the lower deserts and in the mid 60s to low 70s across the higher terrain. Additionally morning lows will be on the rise, going from the 40s (30s) across the lower deserts (higher terrain areas) to start the workweek to the upper 40s to low 50s (low to mid 40s) to end the workweek. Dry conditions will also continue through this upcoming week.

AVIATION

Updated at 1130Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT: No major aviation concerns are expected through the TAF period. Winds will continue to favor the NE through the TAF period. Wind speeds through mid morning will generally be aob 5 kt and increase to around 8-13 kt after that through the remainder of the TAF period. Clear skies will persist.

Southeast California/Southwest Arizona including KIPL and KBLH: No major aviation concerns are expected through the TAF period. Westerly winds will continue at KIPL until going northerly around mid-morning before going back westerly this evening. Wind speeds at KIPL will remain aob 10 kts. At KBLH, winds will continue to be out of the north for the whole TAF period. Speeds at KBLH will generally be around 10-15 kt. Clear skies will persist.

FIRE WEATHER

Temperatures remain below normal today, followed by a warming trend back into an above normal category by the beginning of next week. Temperatures will go well above normal by the middle of this coming week. MinRH values have fallen into a 15-35% range and will remain in that range through this coming week, with overnight recoveries generally between 40-70%. Breezy to locally windy conditions are again anticipated this weekend. However, this time the highest gusts will be across the eastern district where gusts in excess of 40 mph are possible. Winds this weekend are anticipated to maintain more of an easterly component. Highest gusts are expected Sunday morning and afternoon. Wind speeds will return to more seasonable levels next week.

PSR WATCHES/WARNINGS/ADVISORIES

AZ...Freeze Warning until 8 AM MST this morning for AZZ530-533-534- 551>554-556-560>562.

CA...Freeze Warning until 7 AM PST this morning for CAZ560-569.