Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 271017
AFDTWC

Area Forecast Discussion
National Weather Service Tucson AZ
315 AM MST Thur Jul 27 2017

.SYNOPSIS...Daily afternoon and evening thunderstorms will continue
across southeast Arizona and become more widespread into this
weekend. As storm coverage increases, high temperatures will cool
slightly to below normal readings.

&&

.DISCUSSION...We`re currently watching a decaying thunderstorm
complex heading in this direction from southern NM under partly to
mostly cloudy skies. If it gets here somewhat intact, we`ll see a
few showers and perhaps a rumble of thunder across Cochise County by
13Z or 14Z this morning. Otherwise, dry conditions should continue
this morning. WV imagery indicates moisture advecting northward into
Arizona from Sonora, Mexico with high pressure located over central
New Mexico.

Today begins another moistening trend after a brief two-day "break"
in the monsoon pattern compared to the last couple of weeks. Expect
PWAT values to increase again due to southerly/southeasterly mid and
upper level flow as the H3 high becomes quasistationary over
northern New Mexico and the Texas panhandle into early next week.
This will lead to an upswing in showers and thunderstorms, beginning
with the sky islands and areas near the AZ/NM border today and
Friday. We`ll have to watch for embedded vorticity maxima
circulating around the southern periphery of high pressure and into
Arizona which will help to better determine the location and timing
of enhanced convection. Right now, it seems we could see one vort
max push through from the south Friday into Saturday and again early
Sunday morning. In general though, activity today should be slightly
more than what we saw on Wednesday. The official forecast then
gradually increases PoPs westward across the CWA each day through
the weekend. We`ll keep an eye out for potential flash flooding with
the stronger, more persistent cells, especially on days where the
upper level flow is weak. That said, the current GFS/NAM PWAT
forecast is for values less than 1.50 inches through Friday, but
Saturday and Sunday could see a jump to values of 1.6 to 1.8 inches
once again.

Hi-res models early this morning, including the U of A WRF`s and
HRRR, develop scattered convection mainly from Tucson/Nogales
eastward starting around 27/20z. This includes the White Mountains,
with the potential for an organized line of thunderstorms to roll
southwestward off the Mogollon Rim. If this scenario comes to
fruition, the best chance for precipitation making it into the
Tucson area and across the western deserts will be late this
afternoon into this evening. With slightly less atmospheric moisture
and near normal high temperatures this afternoon, the potential will
exist for a few strong wind gusts to occur with any storms which
develop.

With high pressure progged to gradually migrate westward into the
middle of next week, we should maintain a favorable wind pattern
with plenty of available moisture. With that, the official forecast
continues with above climo PoPs through next Wednesday. Difficult to
tell at this juncture exactly which day will be the most active,
though one or two will likely stand out as time goes on. Expect one
more day of near normal high temperatures today, with values
dropping under more cloud cover from Friday into next week.

&&

.AVIATION...Valid thru 28/12Z.
Looks like things will be more active today with showers and storms
expected to develop by early afternoon across much of southeast
Arizona. DUG/OLS could see development shortly after 19Z with a
slightly later onset at TUS. Will mention VCTS at all sites this
afternoon with showers possible into the evening hours. Gusty winds
to 30-40kts possible within TSRA. Aviation discussion not updated
for TAF amendments.

&&

.FIRE WEATHER...
A return to an active monsoon pattern will begin today with daily
shower/storm chances across much of southeast Arizona. As such,
elevated humidities will remain in place through the weekend into
next week with excellent overnight recoveries. Outside of
thunderstorm winds, expect 20-foot winds to remain at or below 15
mph and follow typical upslope/down valley diurnal patterns. Fire
weather concerns are low through at least late next week.

&&

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

&&

$$

French/Leins

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