Area Forecast Discussion
Issued by NWS Flagstaff, AZ
Issued by NWS Flagstaff, AZ
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234 FXUS65 KFGZ 182322 AFDFGZ Area Forecast Discussion National Weather Service Flagstaff AZ 422 PM MST Tue Jun 18 2024 .SYNOPSIS...Seasonal temperatures with typical afternoon winds are expected for the remainder of the week. Chances for showers and thunderstorms return on Thursday and continue each day through this weekend as moisture increases from the southeast. && .DISCUSSION...Lighter southwest winds are taking place this afternoon compared to yesterday as a low pressure trough lifts towards the north and west. However, conditions remain dry with much of northern Arizona near the critical 15% humidity mark. Temperatures are on the "cooler" side than they have been lately, currently near average for this time of year. Winds should calm down just before sunset with near average temperatures and mostly clear skies overnight. For Wednesday, anticipate another hot and dry day with typical afternoon southwest breezes as the trough retrogrades westward allowing a strengthening high pressure system towards the east to migrate westward. Both ensemble and deterministic model guidance continues to show this synoptic progression resulting in enhanced southeasterly flow into the Southwest by Thursday. Along with being on the western fringes of this high pressure system, tropical moisture from a potential tropical storm in southern Texas looks to make its way northeastward during this time. Both the GEFS and EPS suggest an increasing trend in surface dewpoints and the current NBM is on board as well. Because of these trends and agreement in model guidance, confidence has increased in the potential for more moisture resulting in greater chances for showers and thunderstorms to develop each day beginning on Thursday and lasting through the weekend. Thursday looks to have isolated to scattered coverage focused across northeastern Arizona. For Friday and through the weekend, thunderstorms become more scattered and spread westward across much of northern Arizona. Because PWATs and surface dewpoints look to increase significantly during this time (forecast dewpoints in the 50s-60s) the threat for dry lightning has decreased. Even though geopotential heights increase as the high pressure system towards the east strengthens, temperatures look to remain near average for the most part with most locations within the 5 degree range of average for this time of year mainly due to the presence of additional moisture, clouds, and storms. With that said, southeast winds are forecast to increase on Thursday with gusts of 25-35 mph likely at this time. Even with the increase in moisture on Thursday, there could be some areas of near critical fire weather conditions given how dry fuels are right now. Southerly winds remain enhanced on Friday, however, much of northern Arizona should be above 20% humidity in the afternoon with scattered storm coverage. As we head into the weekend, lighter west-southwesterly flow returns as the high pressure system elongates across much of the southern half of the country. Long range ensemble guidance along with WPC`s Days 4-9 Cluster Tool indicate high pressure building and then strengthening over the Southwest by next week. Temperatures look to increase, however, chances for showers and thunderstorms remain in the forecast each day. There are some discrepancies in regards to the model guidance, for example the overall positioning of this high, the strength of the high, and moisture availability, so make sure to keep up to date with the forecast as things evolve. && .AVIATION...Wednesday 19/00Z through Thursday 20/00Z...Expect VFR conditions to persist. Look for SW winds 10-15 kts through 03Z, with light and variable winds returning overnight. After 18Z, expect SW winds 10-15 kts gusting near 20 kts. OUTLOOK...Thursday 20/00Z through Saturday 22/00Z...VFR conditions likely becoming brief MVFR conditions due increasing SHRA/TSRA chances after 18Z Thursday. Greatest chances for showers/thunderstorms will be along and NE of a KGCN-KFLG-KSOW line. Outside of gusty/erratic storm-driven winds, expect S-SW winds 10-25 kts each afternoon becoming light and variable overnight. && .FIRE WEATHER...Wednesday and Thursday...Dry and breezy Wednesday with southwest winds 15 to 25 mph. A bit warmer on Thursday, with increasing clouds and chances for showers and thunderstorms moving in from the east. RH values increase substantially for Thursday. South/southwest winds Thursday, 15 to 25 mph, with gusts as high as 35 mph. Friday through Sunday...Warm, daily chances for showers and thunderstorms. South/southwest winds 15 to 25 mph, with gusts as high as 30 mph Friday, lighter Saturday and Sunday. && .FGZ WATCHES/WARNINGS/ADVISORIES...None. && $$ PUBLIC...LaGuardia AVIATION...Konieczny FIRE WEATHER...Peterson For Northern Arizona weather information visit weather.gov/flagstaff