089 
FXUS65 KTWC 042021
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
121 PM MST Fri Aug 4 2023

.SYNOPSIS...Hot and dry weather will prevail through this weekend.
Increased moisture will bring chances for thunderstorms early 
next week.

&&

.DISCUSSION...An elongated area of high pressure in the upper 
atmosphere stretched AZ to the Gulf of Mexico with a stronger 
center from SE AZ to SW NM. Subsidence under the high has dried
out the atmosphere well below normal levels for early August. 
Thus, heat will be the main story this weekend with the current 
Excessive Heat Warning in all SE AZ counties on track. The
probability of reaching 110+ degrees in Tucson Saturday has 
decreased slightly to 49%. Sunday, the probability is 25%. 

We are seeing a few high based cumulus clouds this afternoon.
Going forecast has a slight chance of a shower or thunderstorm
this afternoon over the Huachucas and Chiricahuas. While latest
HRRR not latching on to this, wouldn't be surprised if a storm
popped over the Chiricahuas in better moisture and just enough
instability. Saturday looks dry area wide as high continues to 
exert its influence. 

On Sunday, will carry small chances for storms mainly south of 
Tucson. However, ensembles show the high holding steady with a 
slight erosion of its western edge not taking place until Monday as
disturbances in northern Mexico trigger thunderstorms and try to 
push NW out of Sonora with an associated a surge of moisture up 
the Gulf of California and a general increase in PWAT values. If 
this occurs, moisture could limit extreme heating. Thus will not 
extend the EHW past Sunday at this time.

Additionally, that moisture would return chances for thunderstorms
to our area as early as Monday or Tuesday. Latest NBM PoPs are
just a bit higher Monday vs Tuesday.

After that, the latest ensembles shift the high further south and
east, putting AZ in southwest flow. That could bring in enough
moisture to keep thunderstorm chances going through the week.

Speaking of moisture to our southwest late next week...an upper 
level disturbance well south of Puerto Vallarta Mexico is forecast
to track WNW through early next week. This path would be farther 
north than this week's hurricane Dora took, but still well south 
and west of Baja. While a direct tropical influence is not 
expected here, perhaps this could be an indirect source of 
moisture for us late next week. By the way, if that disturbance 
intensifies, it would become Eugene.

&&

.AVIATION...valid through 06/00Z. 
SKC through the period except FEW-SCT clouds AOA 15-20k ft MSL
through sunset. Perhaps an ISOLD -SHRA/-TSRA over mts near KDUG 
until 05/01z. SFC wind WLY 10-15kts with gusts up to 20kts til 
05/03z and again Saturday afternoon. Otherwise SFC winds generally
remain under 10 kts and follow diurnal trends. Aviation discussion
not updated for TAF amendments. 

&&

.FIRE WEATHER...Hot and dry conditions through this weekend with
afternoon gustiness, which will dry fuels somewhat. Minimum 
humidities Saturday will be 8 to 16 percent in the lower 
elevations and 12 to 20 percent in the mountains. Increased 
moisture is expected early next week, which will bring back the 
chance for daily rounds of mainly afternoon and evening 
thunderstorms.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM MST Sunday for AZZ501>509.

&&

$$

Drozd

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