270
FXUS65 KBOI 121757
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1157 AM MDT TUE MAY 12 2026
UPDATE
UPDATED AVIATION DISCUSSION.
KEY MESSAGES
- RECORD HIGH TEMPERATURES IN THE 90S ARE EXPECTED ACROSS THE
LOWER VALLEYS TODAY BEFORE A SHARP COOLING TREND ARRIVES
WEDNESDAY.
- BECOMING VERY WINDY AND TURNING MUCH COOLER FROM WEST TO EAST
WEDNESDAY, WITH SHOWERS AND A CHANCE OF THUNDERSTORMS ALONG
AND BEHIND A STRONG PACIFIC COLD FRONT.
- SLIGHTLY WARMER FRIDAY, THEN TURNING COOLER AGAIN SATURDAY
AND SUNDAY, WITH LIGHT SNOW POSSIBLE ABOVE 6000 FEET IN
NORTHERN MOUNTAINS.
SHORT TERM /THROUGH THURSDAY NIGHT/
ISSUED 310 AM MDT TUE MAY 12 2026
UPPER LEVEL RIDGING REMAINS THE DOMINANT FEATURE ACROSS THE
WESTERN UNITED STATES TODAY. THIS WILL RESULT IN RECORD BREAKING
HEAT FOR MANY LOCATIONS, WITH AFTERNOON HIGHS IN THE MID TO
UPPER 90S ACROSS THE LOWER VALLEYS. THESE TEMPERATURES ARE
ROUGHLY 20 TO 25 DEGREES ABOVE SEASONAL NORMALS. HIGH-RES MODELS
INDICATE INCREASING MID-LEVEL MOISTURE ACROSS SOUTH-CENTRAL
IDAHO THIS AFTERNOON, WHICH WILL BE ENOUGH FOR CUMULUS
DEVELOPMENT BUT IS UNLIKELY (10% CHANCE) TO PRODUCE
THUNDERSTORMS.
THE WEATHER PATTERN UNDERGOES A SIGNIFICANT SHIFT WEDNESDAY AS
A DEEP PACIFIC LOW PRESSURE SYSTEM MOVES TOWARD THE OREGON
COAST. AS THE RIDGE SHIFTS EAST TOWARD THE CONTINENTAL DIVIDE, A
STEEP THERMAL AND HEIGHT GRADIENT WILL DEVELOP. THIS
ENVIRONMENT WILL SUPPORT THE FORMATION OF A STRONG SURFACE COLD
FRONT THAT IS EXPECTED TO SWEEP THROUGH THE REGION FROM WEST TO
EAST ON WEDNESDAY. EXPECT STRONG WINDS TO DEVELOP ALONG AND
BEHIND THE FRONT, PARTICULARLY ACROSS SOUTHERN SECTIONS OF OUR
AREA WHERE A WIND ADVISORY HAS BEEN ISSUED. SUSTAINED WINDS OF
25 TO 35 MPH WITH GUSTS UP TO 55 MPH ARE POSSIBLE. THE FAST
MOVING NATURE OF THE FRONT AND DRY LOWER LEVELS COULD LEAD TO
BLOWING DUST AND REDUCED VISIBILITY IN AREAS THAT STAY DRY.
WHILE PRECIPITATION WILL BE LIMITED TO THE MAIN LOW PASSAGE WELL
NORTH OF THE FORECAST AREA, THERE LOOKS TO BE ENOUGH MID-LEVEL
MOISTURE FOR A SLIGHT CHANCE OF THUNDERSTORMS ACROSS SOUTH-
CENTRAL IDAHO WEDNESDAY AFTERNOON. TEMPERATURES WILL TURN MUCH
COOLER BEHIND THE FRONT, DROPPING SIGNIFICANTLY FROM TUESDAY'S
HEAT. SHOWERS WILL CONTINUE WEDNESDAY NIGHT, ESPECIALLY ACROSS
THE NORTHERN MOUNTAINS WHERE SNOW LEVELS WILL BEGIN TO FALL
TOWARD THE HIGHER PEAKS BY THURSDAY MORNING.
ON THURSDAY, THE UPPER LEVEL TROUGH MOVES EAST, LEAVING THE
REGION UNDER A DRIER NORTHWEST FLOW. A 20 PERCENT CHANCE OF
SHOWERS WILL PERSIST OVER THE MOUNTAINS OF SOUTHWEST IDAHO.
BREEZY WEST TO NORTHWEST WINDS WILL CONTINUE THROUGH THURSDAY,
SPECIFICALLY ACROSS THE MAGIC VALLEY, THOUGH WIND SPEEDS WILL BE
LOWER THAN WEDNESDAY. DAYTIME HIGHS ON THURSDAY WILL RETURN TO
NEAR NORMAL VALUES.
LONG TERM /FRIDAY THROUGH TUESDAY/
ISSUED 310 AM MDT TUE MAY 12 2026
COME EARLY FRIDAY, THERE IS STRONG GUIDANCE AGREEMENT THAT OUR
AREA WILL REMAIN UNDER A DRY WEST-NORTHWEST ZONAL FLOW,
CONTINUING A NEAR- NORMAL TEMPERATURE TREND. A SHORTWAVE TROUGH
WILL DIG ACROSS THE AREA FROM OFF THE NORTHWEST COAST SATURDAY
THROUGH SUNDAY. THIS PATTERN WILL BE MOSTLY DRY OVER OUR AREA,
FAVORING SOME LIGHT ISOLATED SHOWERS OVER THE NORTHERNMOST
MOUNTAIN AREAS OF OUR CWA. A COOLING TREND FROM THIS PATTERN
WILL DROP DAYTIME TEMPERATURES 5 TO 10 DEGREES BELOW NORMAL OVER
THE WEEKEND. COME MONDAY THROUGH TUESDAY, THERE IS SOME
GUIDANCE DISAGREEMENT OVER WHETHER THE AREA WILL STAY UNDER A
WEST-NORTHWEST ZONAL FLOW OR BE UNDER ANOTHER DRY SHORTWAVE
TROUGH. FOR NOW, DRY CONDITIONS AND A WARMING TREND TO NORMAL
TEMPERATURES ARE EXPECTED EARLY NEXT WEEK.
AVIATION /18Z TUESDAY THROUGH WEDNESDAY/
ISSUED 1141 AM MDT TUE MAY 12 2026
VFR WITH SCATTERED HIGH CLOUDS. HIGH DENSITY ALTITUDE POSSIBLE
DUE TO HOT TEMPERATURES. SURFACE WINDS INCREASING TO ESE 5-15
KT THIS AFTERNOON, WITH GUSTS 20-25 KT MAINLY OVER SE OR AND
MAGIC VALLEY. AREAS OF LLWS DEVELOPING LATE THIS EVENING.
ISOLATED TO SCATTERED SHOWERS OVER SE OR FROM NEAR KBNO TO KBKE
AND WEST-CENTRAL ID MTNS WEDNESDAY EARLY MORNING AHEAD OF A
COLD FRONT.
KBOI...VFR. WINDS SE 8-11 KT WITH GUSTS TO 15 KT AFTER 20Z.
HIGH DENSITY ALTITUDE POSSIBLE 20Z-WED/01Z DUE TO HOT
TEMPERATURES.
BOI WATCHES/WARNINGS/ADVISORIES
ID...WIND ADVISORY FROM NOON WEDNESDAY TO MIDNIGHT MDT WEDNESDAY
NIGHT FOR IDZ012-014>016-028>030.
OR...WIND ADVISORY FROM NOON MDT /11 AM PDT/ WEDNESDAY TO MIDNIGHT
MDT /11 PM PDT/ WEDNESDAY NIGHT FOR ORZ063-064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
AVIATION.....TL
SHORT TERM...JDS
LONG TERM....JY
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page