Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
082 FXUS65 KPSR 051729 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 1029 AM MST Fri Jul 5 2024 .UPDATE...Updated 18Z Aviation Discussion. && .SYNOPSIS... Prolonged extreme heat and dry conditions will continue through at least early next week with strong high pressure over the region. Most lower desert locations will see daily high temperatures between 112 to 120 degrees with limited overnight relief. A moisture return will bring increased thunderstorm activity back to the Arizona high terrain and southeast Arizona by the middle of next week. && .DISCUSSION... Strong high pressure is currently centered off the NorCal coast with 594-595dm H5 heights over the Desert Southwest. With a fairly stagnant hemispheric pattern the strong high pressure is expected to persist for the next week or longer. Global ensembles show H5 heights remaining around 594-596dm through this weekend and all of next week, with a slow drift of the high center east- southeastward to over the Desert Southwest towards the middle of next week. Under this setup, prolonged extreme heat conditions are expected to continue. Excessive Heat Warnings took effect for most lower desert locations of AZ and Southern CA yesterday and the warning currently extends through Tuesday next week as HeatRisk levels push widespread Major to locally Extreme. With little fluctuation in the synoptic setup, there will be very little day to day change in temperatures as lower desert highs push 112-120F and lows fall to lower 80s to lower 90s. Multiple daily record high and warm low temperatures may be tied or broken during this stretch of extreme heat (see CLIMATE section below). During this stretch please protect yourself from the heat. Hydrate - Hydrate - Hydrate! Avoid strenuous outdoor activities during the afternoon. Do not leave kids, elderly, and pets in hot cars. If you do not have personal access to AC, seek out cooling centers. If you need assistance with heat relief in Maricopa County, call 211. In addition to bringing the heat, the high pressure placement has resulted in dry north to northeast mid-level flow. PWAT values are on the decline. PWAT with the 00Z Tucson sounding has dipped below 1.0" and latest objective analysis shows values are down to 0.8-0.9" in South-Central AZ to Southeast CA. PWATs are forecast to fall even further, down to around 0.6-0.7" this weekend. Normal PWAT values this time of year is 1.0". This lower moisture, along with subsidence, will hinder monsoon thunderstorm activity through early next week. So, when will this hot and dry pattern change? It is difficult to say exactly when the heat will abate, as it will likely be correlated with a return of moisture, clouds, and rain chances. With the center of the strong high pressure sliding eastward to over the Desert Southwest toward the middle of next week, there is potential for excessive heat conditions to continue through the end of next week. On the moisture side of things, global models indicate a shortwave trough will round the top of the strong high and dive through the Southern Rockies into the Southern Plains Monday, around the same time TC Beryl makes landfall in TX. So, an increase in storm activity in NM and West TX and steering flow becoming more northeasterly in NM should help with moisture fluxes back into AZ from the east. Global models do support rising PWAT values again beginning the middle of next week, and reaching back above 1.0" toward the latter half of next week. Still, it may take a few to several days before monsoon thunderstorm activity becomes more favorable again in the South-Central AZ deserts. Activity should increase in Southeast AZ and parts of the Rim country by the middle of next week and NBM reintroduces slight chances (20%) for the South-Central AZ lower deserts by the end of next week. && .AVIATION...Updated at 1730Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: No aviation concerns are expected during the TAF period. Winds will follow typical diurnal trends, with occasional gusts this afternoon in the mid-teens, upwards of 20 kts. Other than a FEW mid-level clouds popping up over high-terrain areas, skies should be mostly clear through Saturday morning. Southeast California/Southwest Arizona including KIPL and KBLH: No aviation concerns are expected during the TAF period. Winds at IPL will favor an E`rly component, with extended periods of variability through this evening. Winds may briefly try to switch out of the SW early tonight, but confidence in that shift is low at this time. At BLH, winds will favor a E/NE direction during the afternoon, before more diurnal trends take over by the evening hours. Mostly clear skies are expected through Saturday morning. && .FIRE WEATHER... Hot and dry conditions will prevail across the area through at least the weekend as strong high pressure settles in from the northwest. Excessively hot temperatures with highs generally between 112-120 degrees are expected across the lower deserts each day through at least early next week. Daily MinRH values through early next week will fall between 5-15% across the lower deserts, while higher terrain areas in Arizona will mostly see 10-20%. Winds will be fairly light and follow diurnal trends, occasionally gusting to 20 mph during the afternoon hours. The combination of the very hot and dry conditions will lead to an increased fire danger threat. && .CLIMATE... Record Highs Phoenix Yuma El Centro --------- ------- ----------- July 5 116 (1983) 116 (1905) 115 (2007) July 6 116 (1942) 117 (2018) 118 (1966) July 7 118 (2017) 118 (2017) 121 (2017) July 8 115 (1985) 118 (1958) 117 (1942) July 9 116 (1958) 119 (1958) 117 (1958) July 10 115 (1958) 118 (1959) 116 (2021) && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Excessive Heat Warning until 8 PM MST Tuesday for AZZ530>555-559. CA...Excessive Heat Warning until 8 PM PDT Tuesday for CAZ560>570. && $$ DISCUSSION...Benedict AVIATION...RW FIRE WEATHER...Benedict/Kuhlman CLIMATE...Kuhlman