Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 241400
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
700 AM MST Mon Jul 24 2017

.UPDATE...
Updated Fire Weather section.

&&

.SYNOPSIS...
Thunderstorm activity can be expected across the region today,
especially over northern and southwestern Arizona. Cloud cover
and a moist atmosphere will lead to cooler temperatures today.
This will be followed by drier southwesterly flow aloft leading to
warmer temperatures along with fewer storms across the region
Tuesday through Thursday. More active monsoon conditions return by
next weekend.

&&

.DISCUSSION...
Convection has begun developing in portions of southwest Arizona
as HRRR and NAM Nest had been indicating. However, there is also
new convection developing over south-central AZ. HRRR only recently
changed it`s mind on keeping things relatively quiet there. Made
upward adjustments to the PoPs and QPF. Cells are not stationary
and anticipate that flash flooding potential will be limited but
there will be some pretty intense short lived showers causing
nuisance flooding.

&&

.Previous Discussion...
After all of last night`s convection, there are multiple MCVs
floating around Arizona. One prominent one is departing northern
Maricopa County early this morning and moving into northern
Arizona. Scattered light showers are the result. Speaking of the
earlier convection, a lot of the 00Z hi-res models did a rather
poor job of depicting it for our area - despite only being a 1-4
hour forecast. There are a variety of different solutions amongst
those models for our forecast area. Some of them, especially the
ones that were so underdone with last evening`s activity, depict
convection redeveloping over south-central Arizona. However,
multiple runs of the HRRR have the focus further west -
specifically over La Paz County. The 06Z NAM Nest does as well.
They appear to be generating convection on the western periphery
of the aforementioned MCV. Have leaned toward this scenario but
still a lot of question about how much destabilization there will
be given all of the cloudiness. With so much moisture in place,
anticipate there will be some sort of showers (if not full fledged
thunderstorms) there. The influence of the mid level inverted
trough should also help to get at least isolated coverage over
other lower elevation locations with better chances higher
terrain. On the back side of the inverted trough, drier air starts
moving in later today. Anticipate that things will be fairly quiet
by early evening if not sooner.

Tuesday through Thursday Sunday...
With a lot less moisture available, look for quiet a downtrend in
PoPs (limited to south-central AZ - mainly higher terrain). Temps
climb as well but not out of hand. Late in the week and over the
weekend, a more favorable flow pattern sets up. Plus it appears
there will be a tropical storm of some sort passing south and west
of Baja which helps advect moisture back into the region. Thus a
gradual return of PoPs from east to west. Temps nudge down as
well.

&&

.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:

Showers and isolated thunderstorms will be off and on from now
through about 22Z this afternoon. Storms aren`t expected to be
strong, but they will be capable of producing some good rainfall.
Activity will be on a downward trend after 22Z, with mostly dry
conditions expected for the remainder of the TAF period. Winds
will primarily be out of the east, with some variableness expected
near showers/storms. Low level cloud decks will be around 5 to 8
kft, with gradual clearing and lifting after 00Z.

Southeast California/Southwest Arizona including KIPL and KBLH:

Showers and isolated thunderstorms will be off and on between 13Z
this morning and 22Z this afternoon. Storms aren`t expected to be
strong, but they will be capable of producing some good rainfall.
Activity will be on a downward trend after 22Z, with mostly dry
conditions expected for the remainder of the TAF period. Winds
will primarily be out of the southeast at KIPL and out of the
south at KBLH, with some variableness expected near
showers/storms. Low level cloud decks will be around 5 to 8 kft,
with gradual clearing and lifting after 00Z.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Wednesday through Sunday:

Storm chances will be minimal on Wednesday with only slight
chances limited to the higher terrain of south-central Arizona.
Humidities and storm chances begin to increase Thursday with
chances reaching southeast California by Saturday. Temperatures
will be near normal Wednesday and Thursday (a bit above normal
near and west of the Lower Colorado River Valley) before beginning
to decrease late this week. Apart from thunderstorms, winds will
follow familiar warm season patterns.


&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.

CA...None.

&&

$$

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DISCUSSION...AJ
AVIATION...Hernandez
FIRE WEATHER...AJ


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