514
FXUS65 KBOI 041608
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1008 AM MDT Fri Jul 4 2025

...MARGINAL RISK FOR SEVERE THUNDERSTORMS AND FLASH FLOODING
THROUGH THIS EVENING...

.DISCUSSION...Instability and moisture along with dynamics
associated with an upper trough will promote rounds of showers
and thunderstorms across the region through this evening. There
is a marginal risk for severe thunderstorms capable of producing
damaging winds and large hail. There is also a marginal risk
for heavy rainfall that may cause flash flooding on burn scars.
The Flash Flood Watch for central Idaho was extended through
this evening, and expanded to include all of SE Oregon.

&&

.AVIATION...Mostly VFR. Rain showers continue to move north
with clouds clearing behind. Scattered thunderstorms in E
Oregon, with coverage increasing into SW Idaho as early as 18z.
Thunderstorms capable of producing heavy rain, hail, 50 kt wind
gusts, and MVFR/IFR conditions. Mtns obscured in precipitation.
Surface winds outside of storms: W-NW 10-20 kt with gusts to 25
kt in the Snake Plain. Winds aloft at 10kft MSL: Variable 10-20,
becoming SW 15-30 kt after 18z.

KBOI...Mostly VFR. 30-40% chance of thunderstorms this
afternoon. Most likely time frame for thunderstorms at terminal
are between Fri/20z-Sat/00z. Hazards with thunderstorms include:
heavy rain, hail, wind gusts of 50 kt, and MVFR/IFR conditions.
Outflows may travel from distant storms. Surface winds outside
of thunder: NW 10- 16 kt with gusts up to 25 kt this afternoon.

Weekend Outlook...Generally VFR. A 15-25% chance of showers and
thunderstorms Saturday morning in W-central Idaho mountains,
then clearing through Sunday. Surface winds variable or NW 5-15
kt.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Sunday night...A strong upper level
positively-tilted shortwave will move into the region today and
help keep thunderstorms going. Most areas can expect multiple
rounds of showers and storms. As of 2 AM MDT, showers and storms
were most numerous south of Boise, but there were additional
showers and storms in the mountains. Mesoscale models are
reasonably consistent showing this activity increasing through
sunrise as storms continue to move north. Latest QPF guidance
continues to show the possibility of high rainfall rates in the
mountains this morning, and the Flash Flood Watch will be
maintained as issued. We considered moving the start time up a
couple hours, but it appears that the strongest rain rates will
occur around and after 12Z, so a change is not needed. Red Flag
Warnings continue across eastern Oregon today, and seem
appropriate based on several bands of thunderstorms that should
move across the region this morning through early evening.
Instability will be extreme for this area, with CAPE values
forecast over 1000 J/kg over a sizable area around midday. Shear
increases today compared to yesterday as the shortwave trough
moves through, and supercells may form, especially this
afternoon. Not coincidentally, SPC has put nearly our entire CWA
into a marginal risk for severe thunderstorms. Some storms are
expected to produce wind gusts 40-60 mph, hail up to 1 inch in
diameter, and brief torrential rain. PW values near 0.90 inch
put us near the 90th percentile this morning, before drier air
moves in this afternoon into the evening. Showers and storms
should continue into the evening before diminishing around
midnight tonight. There is still a slight chance of showers and
thunderstorms in eastern Valley County Saturday, but Sunday
will be dry with a warming trend as temperatures return to near
normal. Temperatures today and Saturday are expected to be
relatively cool for this time of year, with readings in the
lower to mid 80s at lower elevations. Winds should mainly out
of the NW at 5-15 mph today and Saturday except near showers
and thunderstorms.

LONG TERM...Monday through Friday...Strong ridging will build into
the area from the four corners region throughout the long-term,
sustaining hot and dry conditions Monday to Friday. A trough off the
coast of California is expected to keep our area in southerly
flow aloft. As the ridge builds, temperatures take on a
significant warming trend reaching roughly 10 degrees above
normal, with valley daytime temperatures reaching or exceeding
the upper 90s throughout the week. Heat headlines may be needed
in the week to come as a result of the prolonged hot
temperatures. Influxes of upper-level monsoonal moisture steered
by this pattern interaction cannot be ruled out for the
extended period. A slight ridge breakdown is possible Thursday
as the trough off the California coast is expected to briefly
dig across the northwest as a shortwave towards the end of the
week.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Flash Flood Watch until 9 PM MDT this evening IDZ011-013.
OR...Red Flag Warning until 8 PM PDT this evening ORZ670.
     Flash Flood Watch until 9 PM MDT /8 PM PDT/ this evening
     ORZ061>063.

&&

$$

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DISCUSSION...BW
AVIATION.....NF
SHORT TERM...SP
LONG TERM....JY