Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 260900
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
200 AM MST Wed Jul 26 2017

.SYNOPSIS...Following a brief reprieve from thunderstorm chances on
Tuesday, monsoon moisture will increase and bring about a return of
daily shower and storm chances this afternoon through early next
week.

&&

.DISCUSSION...
Early morning water vapor imagery reveals a decaying complex of
storms over Sonora, with quite a bit of cloud cover and moisture
making its way northward into Arizona. Some of this cloud cover is
showing up on radar but nothing has developed in terms of showers or
storms as of 09Z. Blended TPW imagery suggests values close to 1.7-
1.8 inches resides just south of the border. Looks like our period
of drying out is on the cusp of ending.

Exactly how today`s forecast plays out depends if we get any remnant
MCVs or weak inverted troughs from the decaying Sonoran convection.
Past 5 or 6 runs of the HRRR along with UA WRFs suggest a fairly
typical monsoon afternoon with storms developing east of Tuscon
around noon and converging on the city between 3-5 pm. NCAR ensemble
isn`t nearly as enthused about storms making it into Tucson but
agrees that storms are plausible along the AZ/NM border. While I
think it`ll be less active than what we saw last week, today should
see an increase in storm coverage compared to yesterday. PoPs have
been increased slightly on the premise that we`ll see a weak trough
move through the region this afternoon.

Today should see the beginning of the return of deeper moisture
across the area with nearly all deterministic guidance along with
larger scale ensembles pointing to a period of anomalously high PW`s
across the area Thursday through early next week. Hi-res models are
depicting a fairly active day across the area on Thursday, Friday,
and again late Friday night into Saturday morning. Latest blended
00Z guidance has arrived with somewhat higher PoP values than
previous runs and I have trended PoPs upward a bit into the weekend.
By early next week there is are hints that conditions will try and
dry out in the west with storms confined to areas east of Tucson,
although I`m hesitant to buy into much of a drying trend unless we
get a large scale pattern shift w/ southwesterly winds. Since that
doesn`t appear to be in the cards at this point, I`ll hang on to
higher than normal PoPs at all sites into next week.

As for temps, expect highs at or above 100 today in the deserts.
This should be short lived with increased moisture on the way and
highs should only top out in the mid 90s this weekend into next
week.

&&

.AVIATION...Valid thru 27/12Z.
Isolated to scattered -TSRA/-SHRA this afternoon, mainly from
KTUS/KOLS eastward. Otherwise, VFR conditions with cloud decks
generally 5k-10k ft AGL. SFC wind variable in direction mainly less
than 12 kts, except in the vicinity of TSRA where gusts may exceed
35 kts. Aviation discussion not updated for TAF amendments.

&&

.FIRE WEATHER...Isolated to scattered showers and thunderstorms
are expected through Thursday, mainly east of Tucson. An upswing in
thunderstorm activity will occur Friday through this weekend. Near
normal daytime temperatures are expected through Friday with below
normal readings this weekend. 20-foot winds will remain below 15
mph, with the exception of strong outflow winds in the vicinity of
thunderstorms.

&&

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

&&

Leins/French

$$

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