Wildfire in California, June 28 to 29, 2020

Area Forecast Discussion...Updated
National Weather Service Phoenix AZ
500 PM MST Sun Jun 28 2020

.UPDATE...Updated aviation discussion.

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.SYNOPSIS...
Windy and dry conditions can be expected through tomorrow causing
very high fire danger - especially across south-central and
southwest Arizona. Temperatures will drop well below normal as
well. A warming trend begins Wednesday with highs climbing well
above normal over the weekend. Humidity will be higher during
that time as well. In fact, there will be a slight chance of
thunderstorms over the higher terrain of south-central Arizona on
Thursday.

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.DISCUSSION...
Breezy conditions early this afternoon will increase by late
afternoon. Winds later today and this evening will be strongest
over southeast California where a Wind Advisory is in effect.
These winds are being driven by a low pressure system currently
centered over the Pacific Northwest. The center of it will shift
to Idaho on Monday and a vort lobe moving through the southern end
of the trough will brush our area as well. That will keep windy
conditions going on Monday though a bit lighter over some of our
western areas but stronger over some of our eastern areas. The
winds and low humidities are also causing a big increase in fire
danger. Fortunately, the system weakens some on Monday. The system
weakens more noticeably on Tuesday as it starts shifting eastward.
Thus winds will be substantially lighter. The other main effect
of the system passage will be cooler temperatures. In fact, highs
dip into the 90s on the lower deserts.

A strong ridge of high pressure will gradually expand over the
region for the second half of the week with temperatures warming
back above seasonal normals by the weekend. The warmup will be
slowed somewhat by an increase in moisture starting on Wednesday
with more significant precipitable water values in place over
southern Arizona on Thursday. The moisture appears to be the
remnants of a tropical disturbance currently well south-southeast
of Cabo San Lucas. One impact impact for our area will be higher
dew points over much of our forecast area the rest of the week.
There will also be a slight chance of thunderstorms over the
the higher terrain of south-central Arizona on Thursday. Wouldn't
be surprised if things trended such that storm chances expanded to
the adjacent lower deserts. Otherwise, storm chances will be
primarily over northern and eastern AZ (mainly the eastern
quarter of AZ).

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.AVIATION...Updated at 0000Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:

A large area of low pressure moving through the western states today
into Monday will result in periods of rather breezy conditions in
the Phoenix area both days. Expect winds favoring southwest from 20z-
03z with peak gusts 25-30kt at the terminals today and Monday; winds
to gradually taper off after 03z and stay generally west thru about
09z. Winds should transition to the southeast after 08z with
sustained 7-10kt, then begin swinging to the south after 16z with
sustained 10kt or higher before becoming southwest after noon.
Variable amounts of mainly high cirrus can be expected mainly
tonight with less cloud Monday afternoon. Lots of thin BKN decks
tonight with bases aoa 20k feet. At this time do not expect any
visibility restrictions due to blowing dust but we will keep our
eyes on this in cases gusts start to really increase.

Southeast California/Southwest Arizona including KIPL and KBLH:

A large upper trof moving through the area today into Monday will
result in significant wind tonight across the western deserts. Winds
will favor the west at KIPL and the southwest at KBLH; look for peak
gusts to around 35kt at the terminals through about 04z with gusts
tapering off but staying above 20kt well through the night. May see
a bit of blowing dust this evening with visibility lowering to 5-6sm
briefly. Less wind Monday but favoring west again at KIPL and
southwest to west at KBLH. Variable amounts of mainly high cirrus
tonight becoming mostly sunny during the day on Monday.

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.FIRE WEATHER...
Tuesday through Saturday:

Winds will be much lighter on Tuesday relative to Sunday and
Monday as the disturbance responsible for gusty winds exits the
region. However, lingering breeziness over the higher terrain of
south-central Arizona will continue on Tuesday afternoon with more
typical afternoon breezes up to 20 mph expected for Wednesday into
next week. Tuesday will be the coolest day of the forecast period
as temperatures across the lower deserts remain in the upper 90s
before gradually warming back up to near seasonal normals in the
mid to upper 100s by Saturday. Minimum relative humidity will
remain in the teens each day, with the lowest values closest to
10% on Tuesday and Wednesday head of a modest moisture surge on
Thursday when very isolated and mostly dry thunderstorms will be
possible. Maximum humidity values overnight will recover to
around 30-50% with a temporary increase on Thursday night.
Isolated afternoon thunderstorm activity may continue into the
weekend over the higher terrain of southern Gila County.

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

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.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Red Flag Warning until 8 PM MST this evening for AZZ132-133.

     Red Flag Warning from noon to 8 PM MST Monday for AZZ132-133.

CA...Wind Advisory until 11 PM PDT this evening for CAZ560-561-563-
     564-566>568.

     Wind Advisory until 7 AM PDT Monday for CAZ562.

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DISCUSSION...Hopper
AVIATION...CB
FIRE WEATHER...Hopper