Area Forecast Discussion
Issued by NWS Phoenix, AZ
Issued by NWS Phoenix, AZ
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056 FXUS65 KPSR 110019 AFDPSR Area Forecast Discussion National Weather Service Phoenix AZ 519 PM MST Mon Jun 10 2024 .UPDATE...Updated 00z Aviation Discussion. && .SYNOPSIS... Near to slightly above normal high temperatures are expected across the region today. Excessive heat will develop tomorrow across the lower elevations of South Central Arizona as a ridge of high pressure builds along the Arizona and New Mexico border through the middle of the week. Excessive Heat Warnings will be in effect for these lower elevation locations Tuesday through Thursday, before a weather system traverses the region late this week and cools things down by around five degrees on Friday. && .DISCUSSION... Current WV imagery and streamline analysis shows our region between two upper level lows, one centered over East-Central New Mexico and another cutoff low centered southwest of the Southern California Coast. As heights aloft have not yet had time to build downstream of the aforementioned cutoff low, temperatures today will only reach near to slightly above normal values for the date. Highs will range from the low to mid 100s across the lower deserts this afternoon. By tomorrow, 500 mb heights over the region will have increased upwards of 590 dam, and high temperatures in excess of 110 degrees become possible across some of the hotter lower desert locations of South-Central AZ. NBM probabilities for 110+ degree highs peak on Wednesday, with values between 60-80% in the Phoenix Metro Area and a 48% chance of at least tying the daily high at Sky Harbor. Due to the proximity of the cutoff low which will linger offshore through the middle of the week, a gradient in the high temperatures is expected (particularly on Tuesday and Thursday), increasing from west to east across the lower deserts. The coverage of Major HeatRisk has consistently been highest on Wednesday through the past several forecast packages, but since temperatures will be similar on Tuesday and Thursday, Excessive Heat Warnings will be in effect for all 3 days for portions of South-Central AZ. Heading into the end of the work week, the WPC cluster analysis shows great agreement between global ensemble members that the cutoff low will begin to move inland across the Desert Southwest. Ensemble and deterministic guidance show this occurring late Thursday into Friday, which is expected to push temperatures back down to near or slightly above normal readings on Friday. Guidance shows mid-level moisture increasing into the region ahead of the low Thursday, which may be enough for some weak shower development across the AZ high terrain, but for now PoPs remain around 10-15% or less for most places. Additionally, breezy conditions will increase for the latter half of the week in response to the upper low. The increase in winds combined with hot, dry conditions will lead to enhanced fire weather conditions. This weekend, cluster analysis reveals more disagreement on the exact strength and positioning of a broad trough over the Pacific Northwest. Flat ridging over the Desert Southwest is likely following the passage of the cutoff low, allowing for above normal temperatures to return on Saturday. Though uncertainty is still moderate, latest NBM deterministic values have come up to 108-112 degrees for the highs on Saturday and Sunday across the lower deserts. This would lead to widespread Moderate and isolated pockets of Major HeatRisk developing, particularly in Southeast California. && .AVIATION...Updated at 0020Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; VFR conditions forecast through the TAF period. Wind pattern will continue to follow diurnal tendencies, with speeds generally remaining under 10 kts, although some occasional afternoon and early evening gusts into the mid to upper teens can be expected. Light easterly will develop overnight once again. FEW-SCT clouds above 15 kft will prevail through the period. Southeast California/Southwest Arizona including KIPL and KBLH: VFR conditions forecast through the TAF period. FEW-SCT clouds mainly aoa 20 kft can be expected. At KIPL, winds will generally be out of the southeast through most of the period, with the exception of a period of westerly winds during this evening. At KBLH, winds will generally be out of the south. Wind speeds should generally remain aob 10 kts at both sites. && .FIRE WEATHER... Hot and seasonably dry conditions will continue to support a high fire danger across the area through the week. Near to slightly above normal temperatures will continue today before heating up once again heading into the middle part of the week. Winds will continue to generally favor diurnal tendencies with occasional afternoon breeziness of 20-25 mph expected across most of the region. MinRHs ranging between 5-15% with poor to fair overnight recoveries of between 20-45% are expected. Going into the end of the work week, a weather system is expected to traverse the region and bring widespread breeziness on Thursday and gusty winds over the far eastern districts on Friday, along with a low (10% or less) chance for dry thunder over the South-Central AZ high terrain. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Excessive Heat Warning from 10 AM Tuesday to 8 PM MST Thursday for AZZ534-537>555-559-560-562. CA...None. && $$ DISCUSSION...Whittock AVIATION...Young/95 FIRE WEATHER...Whittock/Smith