Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 211014

Area Forecast Discussion
National Weather Service Phoenix AZ
314 AM MST Mon Oct 21 2019

Dry conditions with mostly sunny skies will persist through the
week. High pressure over the eastern Pacific will result in a
warming trend. Temperatures will peak Tuesday and Wednesday with
highs in the low-90s across the lower deserts. Temperatures should
gradually cool through the end of the week, possibly falling below
normal as a disturbance passes by to the northeast.


Surface analysis tonight shows a light north to northeast wind
across parts of the northern Valley, which may lead to morning
temperatures a degree or two cooler than Sunday. Aloft, a stiff
dry northwest flow across the region will be commonplace through
most of the week, between a persistent H5 high centered over the
EPAC and large troughing pattern through the central CONUS. H5
heights will increase slightly through Tuesday, as high pressure
to the west nudges closer to the CA coastline. This will favor
above normal high temperatures through Wednesday, with nearly all
lower desert locations reaching the low-90s Tuesday and Wednesday.
Overnight lows should remain near to slightly below normal with
excellent desert cooling.

There still remains considerable uncertainty regarding the
synoptic pattern beginning Sunday. Models are at least in
agreement with an amplification of the flow pattern across the
Intermountain West, between the EPAC high and longwave trough
across the central CONUS, but diverge on the evolution of the
longwave trough. The GFS keeps the trough as an open wave while
the ECMWF develops a cutoff low over NM. The trough/low
trajectory should remain east of AZ as the high pressure likely nudges
closer to the CA coast, but the decrease in thickness over the
area and strength of a backdoor cold front will dictate
temperatures for the end of the week into the weekend and be the
difference between highs in the upper-80s or highs in the low-80s
to upper-70s. Currently relying on the National Blend which is
currently leaning more toward the GFS solution. Regardless of
which solution ends up most accurate, the forecast remains dry
through the week with no precip expected and the Lower Colorado
River Valley is likely to remain breezy during the afternoons.

A glimpse at early next week there are some indications a more
prolific low pressure system could dig down the western U.S.,
possibly bringing the coldest temperatures of the season. Perhaps
even a shot at precipitation, something many lower desert folk
would love to see.


.AVIATION...Updated at 0551Z

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:

Minimal aviation concerns are expected through the TAF period as
clear skies and light winds will prevail except for brief 15-20
knot gusts tonight and Monday afternoon at KBLH. Winds at the
Phoenix terminals will be light and variable or easterly tonight
for most sites except KDVT where N-NE winds up to 10 knots will
prevail. Westerly 5-10 knot winds should return to the Phoenix
terminals by 19-20Z with stronger gusts not expected. Winds will
generally stay out of the N-NW across southeast California and
southeast Arizona aside from downsloping westerlies at KIPL
through late morning with another period tomorrow evening.

Aviation Discussion not updated for amended TAFs.


Wednesday through Sunday:
Above normal temperatures are expected Wednesday, followed by a late
week cooling trend as an area of low pressure moves through the
southern Rockies. No rain is expected with this system, though
breezy/windy conditions will be possible Thursday/Friday. Forecast
uncertainty remains quite high through the weekend.


Spotters should follow standard reporting procedures.




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