FXUS65 KTWC 200922
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
222 AM MST Tue May 20 2025

.SYNOPSIS...

Temperatures will climb over next several days as a ridge of high
pressure builds over the region. Light winds are expected today
and tomorrow, with breezy winds Thursday into the weekend.

&&

.DISCUSSION...

The upper level pattern over the coming several days will feature a 
transition from northwesterly to zonal flow today, to ridging 
with modest height rises through Thursday. While this ridge 
amplitude will be on the tame side, it will be enough to usher in 
95-100 degree highs in desert locations Wednesday through Friday.
A byproduct of this pattern switch will be a relaxation of the 
pressure gradient, with lighter winds today and Wednesday than 
seen in recent days.

This weekend will see the ridge axis shift eastward into the central 
CONUS, bringing temperatures down a few degrees (though still near 
or above normal). This shift will allow stronger west to southwest 
flow to return over southeastern Arizona, bringing breezy conditions 
Thursday through Saturday. The probabilities of winds strong enough 
for critical fire weather concerns is low, but non-zero with GEFS 
members showing modestly higher probabilities in eastern locations 
on Friday. 

By early next week ensemble models are in good agreement of a 
ridge rebuilding over the western CONUS. This doesn't do much to change
the temperature outlook from the weekend (NAEFS guidance keeps 
temperatures within the ridge aloft below the 90th percentile in 
its climatology), but it does potentially open up a window for 
moist southeasterly flow into Arizona. Ensemble probabilities for 
adequate moisture for convection remain low at this moment, 
however with a week of lead time and associated uncertainty, the 
potential for convection with the threat of dry lightning will 
need to be watched for. 

&&

.AVIATION...Valid through 21/12Z. 

SKC with winds light and terrain driven through the forecast period. 
Winds generally remain under 12 kts, though brief late afternoon 
gustiness possible. Aviation discussion not updated for TAF 
amendments. 

&&

.FIRE WEATHER...

Less wind and a warming trend over the coming days as a ridge builds 
over the region. Highs by Thursday and Friday will be in the lower 
100s from Tucson westward (and upper Gila River Valley) and in the 
90s in the eastern valleys. Elevated 20-foot winds Thursday 
afternoon through Saturday, with the strongest winds on Friday. At 
this time, wind speeds stay below critical fire weather thresholds. 
Single digit RH values at all elevations the next week. 

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

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