380
FXUS65 KFGZ 131914
AFDFGZ

Area Forecast Discussion
National Weather Service Flagstaff AZ
1214 PM MST Thu Jun 13 2024

.SYNOPSIS...From this afternoon through Friday, a passing low
pressure system will bring scattered shower activity, and a
slight chance for thunderstorms. Dry, warm, and breezy conditions
return by the weekend, with a slight cooling trend early next
week.

&&

.DISCUSSION...A well defined upper low was located just off the
coast of San Diego this afternoon, moving slowly toward the
northeast. Southerly flow ahead of this low has induced a surge of
mid level moisture into Arizona, and scattered shower development
is ongoing in southwest Arizona stretching up into portions of
Yavapai and Coconino counties. Most of this activity through the
afternoon should be in the form of virga and light showers,
though a couple lightning strikes have been observed north of Yuma
already. With the hot/dry boundary layer still in place, a few of
these showers could produce strong outflow winds of 40+ mph. As
the upper low moves closer to our area later tonight, cooling
temperatures aloft will steepen lapse rates and allow for a few
thunderstorms to develop and spread northward. Precipitation
amounts are forecast to be fairly minimal overnight, less than
0.10" for most areas that see precipitation at all. By Friday -
the upper low shifts into northeast AZ and then NM/CO by late
afternoon. The chance for showers and thunderstorms continues in
the morning as far south/west as Flagstaff and then will be
focused in northeast Arizona by afternoon. With daytime heating,
scattered thunderstomrs are forecast northeast of a Kayenta to St
Johns line. Temperatures Friday afternoon will be several degrees
cooler and well below Excessive Heat Warning criteria. Shower and
storm chances end by sunset Friday.

Saturday - Heat builds back in briefly as the low departs, and the
next larger western US trough begins to take shape. Ridging builds
between these two features and allows temperatures to rise to well
above normal levels once again. As of now, highs look to remain a
bit below warning criteria but this will need to be monitored.

Sunday through Tuesday - the major feature this period will be a
deep upper low (for mid June) centered over the NW US. Northern
Arizona will be on the dry and windy southern end of this feature,
with heights falling below normal and allowing for a cooling
trend. Southwest winds will increase, with sustained speeds of
15-25 mph and gusts greater than 30-35 mph likely each day. The
combination of gusty winds and low humidity brings the threat of
critical fire weather with the best chances Sun/Mon but Tuesday
will need to be watched too.

&&

.AVIATION...Thursday 13/18Z through Friday 14/18Z...Mostly VFR
conditions will prevail under mid to high level cloud cover. Brief
MVFR conditions are possible throughout the TAF period in isolated
-SHRA, but mostly showers are excepted to be light. Look for SW
 winds 15-25 kts, gusting near 30 kts after 18Z. Light and
 variable winds should return after 06Z. Gusty/erratic winds will
 be possible near storm development, with greater chances for
 -TSRA after midnight.

OUTLOOK...Friday 14/18Z through Sunday 16/18Z...-SHRA/-TSRA will
continue along and NE of a KSJN-KPGA line between 18Z-00Z, with
drier conditions elsewhere. VFR conditions will prevail outside of
areas experience showers/thunderstorms. Winds look to be
generally out of the SW each afternoon, becoming gusty on Sunday.

&&

.FIRE WEATHER...Isolated to scattered showers and thunderstorms
will continue tonight, becoming more focused over E. AZ. on
Friday. Gusty and erratic winds possible near storm development
along with dry lightning. Look for 5-15 mph west-southwest winds
on Friday and breezy southwest winds on Saturday. Minimum RH
values will drop from 10-25% Friday afternoon to 5-15% on Saturday
afternoon. Dry and warm conditions forecast for Saturday.

Sunday through Tuesday...A slight cooling trend will occur Sunday
through the beginning of the week. Look for gusty southwest winds
Sunday, increasing and peaking on Monday. Minimum RH values will
linger in the single digits to mid-teens each afternoon. As a
result, near-critical fire weather concerns likely for the end of
the weekend through the beginning of next week.

&&

.FGZ WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 8 PM MST /9 PM MDT/ this evening
for AZZ005-006-037.

&&

$$

PUBLIC...JJ
AVIATION...Konieczny
FIRE WEATHER...Konieczny

For Northern Arizona weather information visit
weather.gov/flagstaff