Area Forecast Discussion
Issued by NWS Phoenix, AZ
FXUS65 KPSR 302103
Area Forecast Discussion
National Weather Service Phoenix AZ
205 PM MST SAT JUL 30 2016
A humid airmass will remain in place over the Desert Southwest
through at least the middle of next week. The moisture availability,
as well as some weather disturbances, will make for an active period
of weather over the region, with locally heavy rain and gusty winds
possible. A reduction in convective activity is possible towards
the end of next week as drier air attempts to move into the region
from the west.
Tonight through Sunday...
A much quieter late afternoon/evening appears to be on tap for the
rest of today/tonight. In spite of a moist environment (PWATS in
the 1.5-2.0 inch range), a well worked-over boundary layer from last
night`s very widespread convective activity, and warming/drying
through the 500-700mb layer is expected to make it much harder to
get thunderstorms going this afternoon/evening across the lower
deserts. There is also much less wind shear through the column to
provide lift as well. The latest HRRR and NAM 4km high-res models
continue to keep convective activity confined to the higher terrain
east of Phoenix, with perhaps a weak outflow moving into the Greater
Phoenix area later this evening.
As far as tonight and Sunday is concerned, a weak disturbance moving
into the region from the south later tonight/early Sunday is
expected to moisture and increase the winds through the mid-levels
of the atmosphere, which could help to trigger some isolated-
scattered showers/storms across the region, especially over south-
central AZ. Any storms that do develop will be slow-moving, and
capable of producing heavy rains. The activity could continue into
Sunday afternoon/evening, if it does not get too widespread during
the earlier part of the day. Temperatures will likely remain below
normal will considerable cloudiness reducing the amount of solar
radiation reaching the ground.
Monday through Friday... Deep moisture remains over the region
through at least Wednesday night. Models continue to depict easterly
waves/inverted troughs passing by or through, especially on
Tuesday night/early Wednesday when an inverted trough/upper low
tracks right through Arizona. Thus, keeping elevated storm chances
through the period, especially on Tuesday night/Wednesday. The GFS
continues to show a noticeable decline in available moisture starting
on Thursday and continuing into next weekend, as the flow aloft
becomes westerly over the region, while the EURO still hangs on to
some moisture. Temps to remain below normal through Wednesday before
climbing some late in the week.
South-Central Arizona Including KPHX, KIWA, and KSDL: Only minimal
aviation impacts are likely through Sunday morning as most
thunderstorm activity remains over high terrain north and east of
terminals as well as SE AZ. Distinct outflow boundaries may
eventually causes a shift to an easterly sfc wind late
evening/overnight, but timing and magnitude are highly uncertain;
and current thinking suggests a west component will prevail well
into the overnight.
Remnant showers and virga are very possible around sunrise through
the mid morning hours Sunday. Cigs should remain above 6K ft, though
any more organized shower area could result in variable sfc winds
with frequent directional shifts. Confidence is low in attempting to
time out any specificity.
Southeast California/Southwest Arizona including KIPL and KBLH:
Aviation impacts should remain fairly limited with thunderstorm
activity shifting north and west over San Diego and San Bernardino
counties this afternoon and evening. There is only a remote chance
of TSRA moving off the Baja spine towards KIPL. Otherwise, sfc winds
will favor a southerly component and occasionally be somewhat gusty
though generally stay sustained up to 15kt.
Aviation Discussion not updated for amended TAFs.
Tuesday through Saturday... Moisture values will remain quite
elevated through the entire week yielding good to excellent chances
for at least some wetting rains. Thunderstorm coverage will be more
extensive during the first half of the week with occasional gusty
winds and heavy rainfall. More regular thicker cloud cover will also
keep temperatures near to below normal during the week; and
scattered rainfall will force humidity levels above normal. Minimum
humidities in the 25-50 percent range early in the week will drop to
around 15-30 percent by the end of the week. Overnight recovery will
be good to excellent. Outside of thunderstorm wind gusts, wind
speeds will be typically light throughout the day.
.SPOTTER INFORMATION STATEMENT...
Spotter activation could be possible later today.
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