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Area Forecast Discussion (AFD)

Issued by NWS Phoenix (PSR)

FXUS65 KPSR 191745 AAA

Area Forecast Discussion
National Weather Service Phoenix AZ
1045 AM MST Wed Jun 19 2019

Updated 18Z aviation discussion. 


The weather pattern over the next week will remain uneventful with
near normal temperatures lasting through Thursday before gradually
cooling to below normal levels. A weather disturbance to our north
late this week will bring breezy to locally windy conditions, but
it will also lead to high temperatures falling to just below 100 
degrees this weekend.


Seasonably dry and warm conditions will continue into early next
week with the main forecast concern being elevated fire danger
conditions Thursday and Friday. A deep upper level low is set to
slowly dig southeastward through the Interior West tonight into
Friday with models now showing a shortwave trough diving southward
into the Desert Southwest on Saturday. The large scale trough 
will increase flow aloft beginning Thursday with widespread breezy
conditions and gusts of 20-25 mph during the afternoon. Winds 
aloft will be maximized on Friday allowing for afternoon gusts as 
high as 30 mph across southern Arizona and near advisory level 
across portions of southeast California. The breezy to windy 
conditions and afternoon RHs around 10% will definitely enhance 
the fire danger threat both days. Temperatures today and Thursday 
will be right around normal before dropping a couple degrees 
Friday as the trough continues to sag southward toward the region.

Latest model runs are now a bit more aggressive with the 
shortwave trough diving through the Great Basin Friday and the 
Desert Southwest Saturday into Sunday. Saturday will again be a
fairly breezy day, but fire weather concerns will be dampened 
somewhat with a slight increase in RHs and cooler temperatures. 
Highs Saturday have now been lowered into the upper 90s, or 8-10 
degrees below normals. After the shortwave exits to the east on 
Sunday, the flow aloft will become zonal and temperatures will 
start to creep upward again. Another deep Pacific trough is shown 
moving into the Northwest U.S. early next week, but it looks to 
stay well to our north, more so than previous model runs. This 
will likely allow the subtropical high to our south to begin to 
edge northward into our region with 500mb heights surpassing 
590dm by the middle of next week. Temperatures early next week 
should still be a few degrees shy of normals, but the latter half 
of next week may end up being rather hot. There are still no 
obvious signs of any meaningful monsoon activity getting close to 
our region next week, keeping Arizona dry through the end of the 


.AVIATION...Updated at 1745 UTC.

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

VFR conditions with clear skies and diurnal winds to prevail through 
the TAF period. Southerly crosswinds during the late morning/early 
afternoon hours today to be lighter than what we saw yesterday, with 
wind speeds remaining mainly AOB 8 knots. A shift to westerly winds 
will likely occur early than what we saw yesterday as well, most 
likely in the 21-22Z timeframe. A brief period of 15-20 knot gusts 
may occur this evening for the Phoenix sites as westerly winds aloft 
increase. Over southeast California, SE winds will prevail at KIPL 
aside from a period of SW winds this evening, whereas southerlies 
will persist at KBLH with gusts to 15-20 knots this afternoon. 
Otherwise, no aviation concerns are expected.

Aviation Discussion not updated for amended TAFs.


Friday through Tuesday:
A weather system skirting north of the districts will allow notable 
cooling of temperatures over the weekend and into early next week 
with reading pushing back below normal. Despite this, afternoon 
humidity values will still fall near 10% with mostly poor overnight 
recovery (only locally fair recovery at high elevations and parts of 
SE California). In response to the weather disturbance late in the 
week, afternoon winds will be quite breezy Friday with gusts 25-30 
mph common. While remaining below critical thresholds, these winds 
combined with low humidity values and very dry fuels will result in 
an elevated fire danger both days. Somewhat lighter winds with 
merely the typical upslope gustiness will be more common through the 
weekend and early next week. 


Spotter activation is not expected.