971
FXUS65 KFGZ 022109
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
209 PM MST Tue Jul 2 2024

.SYNOPSIS...Drier conditions set in on Wednesday with thunderstorm
chances confined to the White Mountains. From Thursday onward,
expect dry weather and increasing temperatures. A very hot Fourth
of July weekend is on tap and will likely continue into next
week.

&&

.DISCUSSION...Isolated showers and thunderstorms persist across
southern portions of Navajo and Apache counties this afternoon as
a drier, more stable airmass moves in from the north and west.
This activity should continue through early this evening, tapering
by sunset. Slight chances for isolated storms are forecast on
Wednesday, but only across the White Mountains.

A significant warming and drying period takes shape on Wednesday
and will continue through this upcoming holiday weekend. High
confidence exists in a strong high pressure ridge building off the
West Coast on Wednesday and then migrating towards the east
gradually through the weekend. Surface to mid-level flow has
already shifted to the west-northwest this afternoon, becoming
more northerly and breezier to end the week. This synoptic setup
is a monsoon killer as drier, northerly flow will push moisture
out of the Southwest altogether. Afternoon humidity will likely
plummet by Thursday with widespread single digits on Friday.
Humidity looks to remain below 15% each afternoon into next week
with relatively poor recoveries overnight.

As humidity and moisture decrease, temperatures on the other hand
will be increasing during this time as high pressure strengthens.
Daytime highs of 5-10 degrees above average (it happens to be the
warmest time of the year climatologically speaking) return on
Thursday and continue through the weekend. Given the high
confidence in the temperature forecast and the impacts this
anticipated heat will likely have during the Fourth of July
weekend, Excessive Heat Watches have been issued for our lower
valley locations across Yavapai County and from the Grand Canyon
to Marble Canyon for Thursday and Friday. Heat impacts will likely
be felt across all of northern Arizona during this time with a
high to extreme UV Index thanks to minimal cloud cover expected
each day through Sunday.

As we enter into next week, confidence remains on the higher side
in this high pressure system sticking around for the time being.
Conditions look to remain dry and hot through Tuesday, however,
ensemble guidance indicates moisture beginning to sneak back in
from the south and east by the middle of next week. We also will
have to keep our eye on Hurricane Beryl, currently causing major
problems for those in the Caribbean. Even though it is very far
out, long range model guidance shows the storm taking a west-
northwest track and could impact southern Texas. This potential
scenario would result in an influx of moisture from the southeast.
Of course this all depends on the overall track of the hurricane
and the strength of the high pressure system over the West. Lots
of things to think about and watch. Until then, plan on hotter and
drier conditions.

&&

.AVIATION...Tuesday 02/18Z through Wednesday 03/18Z...ISOLD-SCT
SHRA/TSRA south and east of a KPRC-KFLG-KRQE line until 04Z.
Brief MVFR conditions and gusty, erratic winds possible near TS.
VFR conditions otherwise expected with W/SW winds 5-10 kts.


OUTLOOK...Wednesday 03/18Z through Friday 05/18Z...Mainly VFR
conditions, ISOLD MVFR in SHRA/TSRA near KSOW/KJTC Wednesday
afternoon. Winds W around 10 kts on Wednesday, becoming N/NW on
Thursday.

&&

.FIRE WEATHER...This afternoon trough Thursday...Isolated showers
and thunderstorms mainly along the Mogollon Rim and White Mountains,
then again just in the White Mountains on Wednesday. Dry on
Thursday. Winds west/southwest 5-10 mph, becoming west 10-15 mph on
Wednesday.

Friday though Sunday...Hot and dry conditions are expected, outside
of a slight chance for showers and thunderstorms in the White
Mountains on Saturday. Warming temperatures with northwest through
northeast winds 10-15 mph. Afternoon RH values 5-15%, with overnight
recovery 20-40%.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...

Excessive Heat Watch from Thursday morning through Friday
evening for AZZ005-006-037.

&&

$$

PUBLIC...LaGuardia
AVIATION...MAS
FIRE WEATHER...MAS

For Northern Arizona weather information visit
weather.gov/flagstaff