646
FXUS65 KBOI 090915
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
315 AM MDT FRI MAY 9 2025
SHORT TERM...TODAY THROUGH SUNDAY NIGHT
TODAY AND SATURDAY
ARE EXPECTED TO BE THE WARMEST DAYS OF THE SEASON SO FAR, WITH
TEMPERATURES RUNNING 10 TO 15 DEGREES ABOVE NORMAL UNDER A
STRENGTHENING UPPER-LEVEL RIDGE TO THE EAST.
ON SATURDAY, A DEEPENING UPPER-LEVEL LOW APPROACHING THE
PACIFIC NORTHWEST COAST WILL ENHANCE SOUTHWESTERLY FLOW AND DRAW
IN ADDITIONAL MID- AND UPPER-LEVEL MOISTURE. THIS WILL TIGHTEN
THE PRESSURE GRADIENT, RESULTING IN BREEZY SOUTHERLY WINDS
ACROSS THE REGION. THE COMBINATION OF DOWNSLOPE FLOW AND WARM
AIR WILL PUSH VALLEY TEMPERATURES TO NEAR-RECORD LEVELS, WITH
HIGHS IN THE LOW 90S. WHILE MOISTURE REMAINS LIMITED, THERE
APPEARS TO BE ENOUGH ELEVATED MOISTURE (PRECIPITABLE WATER
VALUES IN THE 60TH PERCENTILE) AND INSTABILITY (CAPE AROUND 250
J/KG) TO SUPPORT ISOLATED THUNDERSTORM DEVELOPMENT, ESPECIALLY
OVER THE HIGHER TERRAIN OF SOUTHWEST IDAHO WHERE OROGRAPHIC LIFT
WILL AID INITIATION.
BY SUNDAY, STEEPER LAPSE RATES AND INCREASED UPPER-LEVEL SUPPORT
FROM A STRENGTHENING SOUTHWESTERLY JET WILL SPREAD ACROSS MUCH
OF THE REGION AHEAD OF THE INCOMING LOW. ALTHOUGH MOISTURE
CONTINUES TO BE A LIMITING FACTOR, LIFT AND SHEAR SHOULD BE
SUFFICIENT TO SUPPORT ADDITIONAL THUNDERSTORM DEVELOPMENT, AGAIN
FAVORING THE HIGHER ELEVATIONS DURING THE AFTERNOON AND EVENING.
INVERTED-V SOUNDINGS INDICATE THAT STRONGER STORMS COULD PRODUCE
GUSTY OUTFLOW WINDS. TEMPERATURES ON SUNDAY WILL BE ABOUT 10
DEGREES COOLER THAN SATURDAY, BUT STILL REMAIN ROUGHLY 10
DEGREES ABOVE NORMAL.
LONG TERM...MONDAY THROUGH FRIDAY
WETTER, COOLER, AND WINDY
WEATHER IS IN STORE FOR MUCH OF THE LONG TERM AS A DEEP UPPER LEVEL
LOW SLOWLY MOVES EAST. TEMPERATURES HOLD STEADY AT JUST A FEW
DEGREES BELOW NORMAL, BUT ABOUT 15-20 DEGREES COOLER THAN THE WARMER
DAYS IN THE SHORT TERM. THE WEATHER WILL BE MOST ACTIVE MONDAY
THROUGH WEDNESDAY, WITH AFTERNOON GUSTS OF 20-30 MPH AND
PRECIPITATION EACH DAY. DURING THIS PERIOD, VALLEYS HAVE A 30-40%
CHANCE OF PRECIPITATION EACH DAY AND MOUNTAINS HAVE A 50-70% CHANCE,
HIGHEST IN THE AFTERNOONS. CONVECTION MAY STRUGGLE WITH CLOUDS AND
COLDER SURFACE TEMPS, BUT MODELS SHOW MARGINAL CAPE MONDAY AND
TUESDAY AFTERNOONS SO THUNDERSTORMS AND STRONG SHOWERS CAN'T BE
WRITTEN OFF. COLD TEMPS WILL DROP SNOW LEVELS TO 6000-7000 FT MSL,
SO HIGH ELEVATION PASSES COULD SEE A COUPLE INCHES OF WET SNOW
ACCUMULATION.
THE UPPER LEVEL LOW WILL MOVES EAST WEDNESDAY NIGHT, AND MODEL
SOLUTIONS DIVERGE SIGNIFICANTLY THURSDAY AND FRIDAY. WE ARE LIKELY
TO SEE TEMPS CONSISTENT WITH THOSE EARLIER IN THE WEAK AS THE FLOW
AMONG MODELS IS MOSTLY ZONAL. CLOUDS ARE ALSO LIKELY TO STICK
AROUND, BUT THE MOST UNCERTAINTY LIES IN THE CHANCE OF
PRECIPITATION. THE EC HAS ANOTHER LOW AMPLIFYING AS IT MOVES ONTO
THE COAST BRINGING MORE PRECIP FRIDAY EVENING, WHILE THE GFS SHOWS A
WEAK SHORTWAVE AND A MUCH LOWER CHANCE OF PRECIPITATION.
AVIATION
VFR. SURFACE WINDS: VARIABLE LESS THAN 10 KT,
BECOMING SW-SE 5-10 KT THIS AFTERNOON. WINDS ALOFT AT 10KFT MSL: SW
10-20 KT.
KBOI...VFR. WINDS SE 5-10 KT WITH SOME VARIABILITY THIS AFTERNOON.
WEEKEND OUTLOOK...INCREASING CLOUDS SATURDAY, WITH A 30% CHANCE OF
SHOWERS AND STORMS IN THE S BOISE MTNS AND ID/NV BORDER THAT
AFTERNOON/EVENING. SUNDAY, A COLD FRONT WILL MOVE FROM OR TO ID,
BRINGING SCATTERED SHOWERS AND STORMS TO MOST OF THE AREA, GUSTY
WESTERLY WINDS, AND LOWER CEILINGS.
BOI WATCHES/WARNINGS/ADVISORIES
ID...NONE.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
SHORT TERM...JDS
LONG TERM....JM
AVIATION.....JM
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