Area Forecast Discussion
Issued by NWS Phoenix, AZ
FXUS65 KPSR 250932
Area Forecast Discussion
National Weather Service Phoenix AZ
232 AM MST Tue Apr 25 2017
A series of mainly dry weather disturbances from the Pacific will
move through the western states through early next week. These
systems will keep afternoon temperatures near or slightly below
normal, along with providing for breezy to windy conditions. One
stronger disturbance on Friday has the potential to produce a
slight chance of afternoon showers over the eastern Arizona
Winds continue to be rather breezy to even windy in some locations
early this morning. The strongest winds currently are focused
across SE California where a few locations continue to see gusts
above advisory level. Winds will remain breezy through the rest of
the day across SE California, but fall below advisory level
shortly after sunrise. Deepening surface low pressure today over
eastern New Mexico and the panhandle of Texas will bring a
tightening pressure gradient over Arizona allowing winds to pick
up by late morning across southern Arizona. Latest model guidance
points toward a rather windy day across southern Arizona with
gusts exceeding 40 mph in some locations this afternoon and early
evening. As a result, we have issued a Wind Advisory for the
majority of Maricopa and Gila counties. Due to the combination of
the windy conditions and very dry surface conditions, a Red Flag
Warning is also in effect for much of south-central Arizona this
Large scale troughing has settled over the Interior West since
Monday. Current water vapor imagery shows a strong but mostly dry
shortwave trough tracking southeastward through the Great Basin.
This shortwave will track through the Four Corners area by late
this afternoon, but limited moisture availability will keep any
shower activity north and east of our CWA. The cooling trend since
Sunday will continue today as highs will only reach into the
middle to upper 80s across the lower deserts.
Once the shortwave trough exits the region tonight we will be
under subtle ridging aloft for Wednesday and the first part of
Thursday, but height packing aloft will remain tight. This will
help to keep breezy conditions across much of the area on
Wednesday and Thursday, but below advisory level. The slight
boost in heights aloft will also allow for some warming with
widespread lower desert highs reaching into lower 90s by Thursday.
The large scale trough over the Interior West will again sag
southward into our region by Thursday night as a strong upper
level jet max digs along the back side of the trough. There
remains a decent amount of model spread Friday into this weekend,
but the overall trend has been for the next trough to stay a bit
further north than the previous model runs, though not enough to
change our forecast for strong winds. Confidence is fairly high
for a near repeat of today with Wind Advisory level winds
affecting much of southern Arizona as well as a strong possibility
of Red Flag Warning conditions. Though moisture availability will
be limited, we can`t rule out at least a slight chance of showers
across southern Gila county mainly Friday afternoon.
A decent cool down is likely Friday into Saturday as the trough
will be slow to move out of the region. Most lower desert
locations should only get into the lower 80s on Saturday with some
middle 80s across SE California. Another breezy day on Saturday
will likely bring more elevated fire weather concerns, but winds
should remain below advisory level. Seems very possible there
will be a near repeat scenario early next week as weak ridging
builds into the Desert Southwest Sunday into early Monday followed
by yet another trough digging through the Great Basin and the
Four Corners area sometime early next week. This should at least
keep our temperatures at or near seasonal normals, but also bring
another round of breezy to windy conditions.
South-Central Arizona Including KPHX, KIWA, and KSDL: Winds will
remain generally out of the west overnight and into tomorrow.
Wind gusts will become more frequent and stronger by late morning,
with gusts to 30-35 kt possible after 21Z. A dry cold front will
arrive during late afternoon, and not out of the question to see
gusts exceeding 35 kt between 23-02Z. Will have to monitor for the
potential for an airport weather warning during this period.
Otherwise, thicker high clouds around 25-30 thousand feet should
persist into the morning hours, before becoming more scattered in
coverage during the afternoon.
Southeast California/Southwest Arizona Including KIPL and KBLH:
Westerly wind gusts up to near 20 kts remain possible overnight.
Winds should gradually veer towards a northwesterly direction as a
dry cold front moves through the area. Wind gusts will become less
frequent by afternoon as the cold front shifts east into Arizona.
Thicker upper-level cloud cover will also shift east of the area
by late tomorrow morning.
Aviation discussion not updated for amended TAFs.
Wednesday through Sunday:
Temperatures will continue to hold at or above seasonal averages,
with minimum RH values mostly below 15 percent as dry northwest
flow aloft persists over the area. After Wednesday, a gradual
cooling trend will settle into the region as mostly dry storm
systems sweep through the Great Basin and down through the
Southwest. Outside of a slight chance at some light showers over
high terrain of Gila County Friday into Saturday, widespread dry
weather will cover the districts. Dry afternoons with 5-15% will
be common with overnight humidities varying between mostly fair to
good. Active storm track through the West will keep afternoons
breezy for the district, with upslope west winds and occasional
gusts possible through week`s end.
There will be potential for widespread dangerous fire weather
conditions Friday into Saturday as windy conditions develop across
most of the area - especially south-central Arizona on Friday - and
minimum RH values drop into the single digits across much of the
lower desert. The cooling trend may help mitigate some of the fire
danger potential however but this is something to keep our eyes on
as we move towards the latter part of the week.
.SPOTTER INFORMATION STATEMENT...
Spotter activation will not be needed through the middle of next
AZ...Red Flag Warning from 2 PM this afternoon to 8 PM MST this
evening for AZZ132.
Wind Advisory from 1 PM MST /1 PM PDT/ this afternoon to 8 PM
MST /8 PM PDT/ this evening for AZZ534-537-538-540>563.
CA...Wind Advisory until 7 AM PDT this morning for CAZ562-566.
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