Area Forecast Discussion
Issued by NWS Phoenix, AZ
FXUS65 KPSR 301147
Area Forecast Discussion
National Weather Service Phoenix AZ
447 AM MST SAT JUL 30 2016
.UPDATE...Updated Aviation Discussion...
A humid airmass will be in place over the Desert Southwest this
weekend and much of next week. The moisture availability, as well as
some weather disturbances, will make for an active period of weather
over the region. All typical hazards associated with the monsoon
season including strong damaging winds, blowing dust, lightning, and
localized flooding will be in play.
Today through Sunday...
Runoff over portions of southwest Maricopa County continues.
Surprisingly, Waterman wash has not trended down yet. Will probably
need to extend the areal flood warning. Storm activity hasn`t ended
for the night as there is a batch of activity over southern Mohave
and northern La Paz Counties going early this morning. This activity
originated over southern Nevada (apparently aided by a weak wave in
the westerlies). Through propagation toward richer moisture as well
as interaction with outflow from earlier storms over our area, the
storms have tracked southward. HRRR has been trending toward a
continued southerly expansion of convection over La Paz and Yuma
counties the rest of the morning. Earlier runs had it dissipating
closer to northern La Paz. Big question for today is how much CIN
will there be. Typically after and active night, there tends to be
too much CIN (even if there is a lot of CAPE). However, much of our
area only got outflow winds and no rain - especially southwest AZ and
southeast CA. Latest RAP and 06Z NAM and GFS all depict areas of
breakable CIN this afternoon - even over south-central AZ deserts
though there are also areas that have higher CIN (greatest toward
Yuma). With another active day over the higher terrain of Central AZ,
anticipate that there is still a chance for storms over the Valley
floors. Went above guidance for southwest AZ and southeast CA. Model
CAPE not looking quite as good Sunday but still good enough for
storms. If today winds up being a down day, then Sunday will be
looking better. Temps today will be lower everywhere. Trends for
Sunday of course will depend upon today`s activity. But, temps look
to be below normal east of the Lower Colorado River Valley.
Monday through Friday...
Deep moisture remains over the region through at least Wednesday.
Models depict easterly waves/inverted troughs passing by or through -
especially Tuesday into Thursday where an inverted trough/upper low
tracks right through Arizona. Hard to hang one`s hat on that
scenario but it`s entirely possible. End result is that storm chances
continue. GFS depicts some decline of moisture beginning Thursday
while the ECMWF hangs on to it as it is slower to eject the low.
Temps are near to below normal through Wednesday before climbing some
late in the week - most noticeably over south-central AZ.
South-Central Arizona Including KPHX, KIWA, and KSDL:
After all the activity on Friday, today should be a less active day,
but late afternoon and evening storms will still be possible. Winds
this morning will be variable at times due to all the leftover weak
outflows and the lack of a strong downslope push. Wind forecast for
this afternoon and evening is of low confidence overall as the
potential for outflows is there, but timing and speeds are
problematic at this point. Outflow strength will be somewhat muted
compared to yesterday due to an increase in low level moisture.
Overall chances of showers and thunderstorms is still decent, but
lack confidence to include in area terminals for the 12Z TAFS.
Southeast California/Southwest Arizona including KIPL and KBLH:
A period of showers and thunderstorms is likely to affect both KBLH
and KIPL this morning, but not anticipating strong wind gusts. These
storms should move out or dissipate by mid morning. Though the chance
is fairly low, can`t rule out another round of storms later today
near area terminals. Winds the rest of the period should mostly
follow a southerly component and be gusty at times.
Aviation Discussion not updated for amended TAFs.
Monday through Friday...
Deep southerly to southeasterly flow aloft is expected to push
copious amounts of monsoon moisture into the region, resulting in
scattered to numerous thunderstorms Monday through Wednesday with
good to excellent chances for at least some wetting rains and locally
gusty winds. The combination of considerable cloudiness and rainfall
will also keep temperatures below normal during this period, and
humidities above normal. A shift to more westerly winds aloft is
then expected to gradually reduce moisture levels, and chances for
wetting rains during the Thursday-Friday period, while allowing
temperatures to return to near-normal levels. Minimum humidities in
the 25-45 percent range in the Monday-Wednesday period to drop into
the 20-35 percent range by Friday, with good-excellent overnight
recoveries. Outside of thunderstorms, winds to mainly follow typical
.SPOTTER INFORMATION STATEMENT...
Spotter activation could be possible later today.
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