Areal Flood Warning 13, NWS Phoenix, AZ

Area Forecast Discussion
National Weather Service Phoenix AZ
458 AM MST Sun Aug 13 2017

.UPDATE...Updated Aviation Discussion...

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.SYNOPSIS...
Sufficient moisture remains in place this weekend supporting at
least a few showers and thunderstorms across central and eastern
Arizona. On Monday, a drying trend will end storm chances across the
lower elevations with only limited chances remaining across the
higher terrain. After Tuesday and through the end of the week,
mostly clear skies and dry conditions will prevail with near normal
temperatures.

&&

.DISCUSSION...
Well, the westerlies (which are expected to bring a substantial
drying trend into the area by early this week) have thrown a
curveball weather-wise with "transition-event" type weather
affecting the area for much of last evening and into the early
morning hours today. A disturbance embedded in the westerly flow
yielded better than expected dynamics along with impressive 300mb
divergence (as seen in the SPC mesoanalysis graphics) and produced a
large MCS across south central Arizona. Widespread showers and
thunderstorms have raked the central deserts since late yesterday
evening and the storms are still firing at 3 am. We have issued
numerous flood advisories and flash flood warnings, many of which
remain in effect. Weather has simply been too active to devote much
time to the upcoming forecast, so much of it remains the same as the
previous package. Trends look unchanged, with few if any storms
expected in the area by Tuesday afternoon. With moisture still in
place across south central AZ today, despite the increasing westerly
flow there remains a decent chance for storms today into tonight and
we raised our POPs accordingly. Temps today will stay a few degrees
below seasonal normals over the central deserts due to the clouds
and showers and the effect of this morning rains over the deserts.

Tuesday through Friday look be exceptionally dry for August with
surface dewpoints falling into the 40s and PWATS in a 0.25-0.75 inch
range. Even though we dry out, temperatures will be hindered by
unusually low heights and thicknesses aloft. In fact, H5 heights
only in a 584-588dm range will be common much of the week (typical
for late September, not mid August). Thus, high temperatures near
seasonal normals (or even a few degrees below) seem very likely with
overnight lows locally dipping to a few degrees below normal due to
the drier airmass and efficient nocturnal cooling. Some moisture may
start to seep back into southern Arizona as early as Friday, but
more likely by Saturday as the flow begins to shift more out of the
south to southeast.

&&

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

Scattered showers with an isolated thunderstorm or two will
remain in the area through just after sunrise this morning. Mid
level CIGs will scatter out by late morning. Thunderstorm chances
look to be substantially less for this afternoon/evening, but
can't completely rule out an isolated storm sometime this evening
into early tonight.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation concerns over the next 24 hours as winds remain
southerly at KBLH and from the southeast at KIPL through this
afternoon before turning out of the west.

Aviation discussion not updated for amended TAFs.

&&

.FIRE WEATHER...
Tuesday through Saturday:
Unusually dry air will settle over the districts during this time
frame with almost no chance of showers or thunderstorms through the
week. Unlike most mid-monsoon breaks, temperatures will stay near
the seasonal average. With the introduction of drier air, minimum
afternoon humidity levels will fall back to a 10-20% range though
overnight recovery will remain fair to good. Upslope afternoon wind
gusts will be stronger than typical monsoon season levels Tuesday
and Wednesday with the passage of a early fall-like weather
disturbance through northern Arizona.

&&

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

&&

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

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DISCUSSION...CB/MO/Kuhlman
AVIATION...Kuhlman
FIRE WEATHER...MO

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
154 AM MST SUN AUG 13 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0111 AM     FLASH FLOOD      3 SSW GUADALUPE         33.32N 111.97W
08/13/2017                   MARICOPA           AZ   LAW ENFORCEMENT

            WATER RESCUE NEAR I-10 AND RAY RD.

&&

CK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
246 AM MST SUN AUG 13 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0226 AM     FLASH FLOOD      2 ENE TOLLESON          33.46N 112.22W
08/13/2017                   MARICOPA           AZ   LAW ENFORCEMENT

            WATER RESCUE AT I-10 AND N 75TH AVE.

&&

CK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
323 AM MST SUN AUG 13 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0318 AM     FLASH FLOOD      1 SW GLENDALE           33.52N 112.20W
08/13/2017                   MARICOPA           AZ   LAW ENFORCEMENT

            WATER RESCUE NEAR N 67TH AVE AND W BETHANY
            HOME RD.

&&

CK