740
FXUS65 KBOI 160313
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
913 PM MDT THU MAY 15 2025
DISCUSSION
A WELL DEFINED SHORTWAVE TROUGH IS PUSHING INTO
THE PAC NW THIS EVENING. RADAR IMAGERY IS REVEALING WIDESPREAD
LIGHT SHOWERS ACROSS WESTERN OR/WA WITH ISOLATED SIGNATURES
ACROSS EASTERN OREGON. BEST CHANCE FOR PRECIPITATION REMAINS IS
IN THE OVERNIGHT AND EARLY MORNING HOURS ACROSS SE OREGON AND SW
IDAHO. SHOWERS WILL LINGER IN THE MOUNTAINS THROUGH FRIDAY
AFTERNOON. THE CURRENT FORECAST HAS IT WELL HANDLED, SO NO
UPDATE FOR THIS EVENING.
AVIATION
VFR THROUGH EARLY OVERNIGHT HOURS. MVFR CONDITIONS
POSSIBLE (20-40%) FROM LOW CEILINGS WITH RAIN SHOWERS AS THEY
MOVE THROUGH SE OR FROM 05Z-14Z, ENTER SW ID AROUND 10Z AND
CLEAR OUT OF LOWER ELEVATIONS BY 18Z. PRECIPITATION CHANCES
LINGER IN HIGHER ELEVATIONS THROUGH 00Z SATURDAY. CLOUD COVER
INCREASING FROM WEST TO EAST. MVFR CONDITIONS AND MOUNTAIN
OBSCURATION POSSIBLE IN SHOWERS. SURFACE WINDS: W-NW 5-12 KT
GUSTING UP TO 20 KT NEAR KTWF/KJER DURING AFTERNOON. WINDS ALOFT
AT 10KFT MSL:
W-NW 10-20 KT.
KBOI...VFR. MVFR CONDITIONS POSSIBLE (20-35% CHANCE) WITH RAIN
SHOWERS DURING MORNING. CEILINGS TO RISE DURING AFTERNOON.
SURFACE WINDS: W-NW 3-6 KT OVERNIGHT INCREASING TO 8-13 KT
AFTERNOON.
WEEKEND OUTLOOK... VFR TO MVFR AND A SLIGHT CHANCE OF IFR
SATURDAY WITH WIDESPREAD PRECIPITATION AND ISOLATED
THUNDERSTORMS, ESPECIALLY DURING THE AFTERNOON HOURS. MOUNTAINS
OBSCURED AT TIMES. SNOW LEVELS 6500-8000 FT MSL FRIDAY,
7000-8500 FT MSL SATURDAY. PRECIPITATION MOVES OUT FROM WEST TO
EAST SUNDAY, WITH IMPROVING CONDITIONS (MOSTLY VFR, BUT MOUNTAIN
OBSCURATION STILL LIKELY). SURFACE WIND INCREASING TO 15-30 KT
GUSTING UP TO 25-40 KT SUNDAY. SNOW LEVELS FALLING TO 5000-7000
FT MSL SUNDAY.
PREV DISCUSSION
SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT...THERE IS STILL
SOME RESIDUAL MOISTURE FROM THE UPPER TROUGH TO OUR EAST,
RESULTING IN ISOLATED SHOWERS IN THE WEST CENTRAL MOUNTAINS EAST
OF MCCALL THROUGH THIS EVENING. THE NEXT (WEAKER) UPPER TROUGH
RESIDES IN A NORTHWEST FLOW ALOFT, CURRENTLY SITUATED NEAR THE
PACNW COAST. SHOWERS WITH THE TROUGH SPREAD ACROSS SE OREGON
TONIGHT AND SW IDAHO ON FRIDAY, ALTHOUGH PRECIP AMOUNTS WILL BE
LIGHT AND FAVOR THE HIGHER ELEVATIONS. LITTLE TO NO RAINFALL IS
EXPECTED IN THE SNAKE RIVER PLAIN. THERE IS ABOUT A 6 HOUR DRY
PERIOD FRIDAY EVENING AFTER THE FRIDAY TROUGH DEPARTS AND THE
NEXT (STRONGER/WETTER) TROUGH SPREADS WIDESPREAD SHOWERS INTO
THE REGION LATE FRIDAY NIGHT THROUGH SATURDAY. PRECIP TOTALS OF
AROUND A QUARTER OF AN INCH IN THE VALLEYS AND A QUARTER TO HALF
INCH IN THE MOUNTAINS ARE EXPECTED. LOCALLY HIGHER AMOUNTS ARE
POSSIBLE, MAINLY IN THE MOUNTAINS. INSTABILITY WITH THE SYSTEM
COULD LEAD TO THUNDERSTORMS, WITH CHANCES GENERALLY IN THE 15 TO
30 PERCENT RANGE. TEMPERATURES REMAIN 5 TO 10 DEGREES BELOW
NORMAL. THE COOLEST DAY WILL BE SATURDAY WITH HIGHS MAINLY IN
THE 50S TO LOWER 60S.
LONG TERM...SUNDAY THROUGH THURSDAY...PRECIPITATION CONTINUES
SUNDAY AS THE UPPER TROUGH CLOSES OFF A CUT-OFF LOW OVER OUR
AREA. PRECIPITATION CHANCES RANGE FROM 60-90% ACROSS HIGHER
TERRAIN AND FROM 20-40% IN LOWER ELEVATIONS, GENERALLY
INCREASING AS YOU MOVE FROM EASTERN OREGON INTO IDAHO. WITH THE
COLD CORE OVERHEAD AND SOME INSTABILITY (<100J/KG OF CAPE)
BUILDING IN SUNDAY AFTERNOON, THUNDERSTORMS AREN'T OUT OF THE
QUESTION WITH A 20% CHANCE ACROSS MOST OF OUR AREA. WINDS
INCREASE AND APPROACH ADVISORY CRITERIA AS A PRESSURE GRADIENT
TIGHTENS ACROSS OUR AREA. SUSTAINED WINDS OF 20-30 MPH GUSTING
UP TO 40 MPH WITHIN THE SNAKE PLAIN. PRECIPITATION MAKES ITS
WAY OUT OF OUR AREA THROUGH MONDAY MORNING AS A WEAK UPPER LEVEL
RIDGE BUILDS IN. TUESDAY AFTERNOON THIS RIDGE BREAKS DOWN INTO
A MORE ZONAL FLOW REGIME. WHILE MOST OF OUR AREA WILL REMAIN DRY
THROUGH THURSDAY, SHORTWAVES EMBEDDED IN THE ZONAL FLOW MAY
BRING PERIODS OF HIGHER PRECIPITATION CHANCES ACROSS HIGHER
TERRAIN. TEMPERATURES INCREASE FROM 10 DEGREES BELOW NORMAL ON
SUNDAY, MAKING IT TO NEAR NORMAL COME THURSDAY. SNOW LEVELS
FOLLOW A SIMILAR TREND, INCREASE FROM 4-5 KFT ON SUNDAY TO 7-9
KFT ON THURSDAY.
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
DISCUSSION...DG
AVIATION.....CH
SHORT TERM...BW
LONG TERM....NF
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