208
FXUS65 KBOI 182042
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
242 PM MDT MON MAY 18 2026
KEY MESSAGES
- FROST ADVISORY FOR THE WESTERN MAGIC VALLEY TUESDAY MORNING.
- LIGHTER WINDS AND DRIER WITH A GRADUAL WARMING TREND THROUGH
WEDNESDAY.
- GENERALLY DRY WITH ABOVE NORMAL TEMPERATURES THROUGH THE
WEEKEND. POTENTIAL PATTERN CHANGE EARLY NEXT WEEK.
SHORT TERM /THROUGH WEDNESDAY NIGHT/
THE AFTERNOON/EVENING SHOWERS AND ISOLATED THUNDERSTORMS WILL
DIMINISH WITH SUNSET, AS WILL THE GUSTY WINDS. LIGHTER WINDS AND
CLEAR SKIES OVERNIGHT ALLOW FOR POSSIBLE FROST IN THE WESTERN
MAGIC VALLEY TUESDAY MORNING. THERE IS A SPREAD IN FORECAST LOW
TEMPERATURES WITH A RANGE OF 33 TO 38 IN THE GOODING/JEROME/TWIN
AREA SO COVERAGE COULD BE PATCHY. HAVE OPTED WITH A FROST
ADVISORY TO HIGHLIGHT THE POTENTIAL. BUILDING HEIGHTS BEHIND THE
EXITING TROUGH WILL BRING A GRADUAL WARMING TREND WITH HIGH
TEMPERATURES CLOSE TO NORMAL BY WEDNESDAY. MOUNTAINS WILL SEE AN
AFTERNOON CUMULUS FIELD FROM DAYTIME INSTABILITY. CAN'T RULE
OUT A MTN TOP SHOWER OVER W-CENTRAL IDAHO MTNS (EAST OF MCCALL-
LOWMAN-ATLANTA LINE) EACH AFTERNOON, BUT IT WOULD BE LIGHT WITH
HEAVIER DEVELOPMENT FURTHER NORTH AND EAST. AN APPROACHING
TROUGH WILL INCREASE PRECIPITATION CHANCES ACROSS THESE AREAS
WEDNESDAY NIGHT. WINDS SETTLE DOWN TUE/WED STAYING BELOW 15 MPH
FOR MOST SITES.
LONG TERM /THURSDAY THROUGH MONDAY/
COME THURSDAY, A SHORTWAVE EMBEDDED IN THE NORTHWESTERLY FLOW
ALOFT WILL BEGIN TO DIG INTO SOUTHEASTERN IDAHO. WHILE THE
BETTER FORCING ASSOCIATED WITH THIS SHORTWAVE WILL BE EAST OF
OUR AREA, HEIGHT FALLS ALOFT WILL SUPPORT ISOLATED SHOWERS
DEVELOPING OVER HIGHER TERRAIN IN THE WEST CENTRAL AND BOISE
MOUNTAIN ZONES. FOLLOWING THIS TROUGH, DRY NORTHWEST FLOW WILL
RETURN WITH HIGHER PRESSURE BUILDING IN ALOFT OVER THE PACIFIC;
AS A RESULT, A WARMING TREND WILL SET IN THROUGH THE WEEKEND,
WITH TEMPERATURES 5-10 DEGREES ABOVE NORMAL.
COME SUNDAY, FLOW ALOFT WILL BECOME MORE ZONAL AS A GULF OF
ALASKA LOW DEEPENS. THE EXACT TRACK OF THIS LOW IS A BIT
UNCERTAIN THIS FAR OUT; HOWEVER, THE GRAND ENSEMBLE SHOWS THE
INDICATION OF TROUGHING MOVING ACROSS OUR AREA COME EARLY NEXT
WEEK (DETERMINISTIC GUIDANCE VARIES ON STRENGTH AND TRACK).
DESPITE THE UNCERTAINTY, THE SIGNAL IS THERE FOR A PATTERN
CHANGE EARLY NEXT WEEK, THIS WILL LEAD TO INCREASING
PRECIPITATION CHANCES AND COOLER TEMPERATURES (ALTHOUGH STILL
LEANING ABOVE NORMAL) COME MONDAY. WITH THE MAIN JET STREAM
ABOVE OUR AREA THROUGHOUT THE LONG-TERM PERIOD, BREEZY
CONDITIONS WILL STICK AROUND EACH AFTERNOON. THE WINDIEST
CONDITIONS OF THE PERIOD WILL LIKELY COME EARLY NEXT WEEK AS THE
LOW MAKES IT'S WAY INTO OUR AREA.
AVIATION /18Z MONDAY THROUGH TUESDAY/
ISSUED 1155 AM MDT MON MAY 18 2026
VFR. SCATTERED SHOWERS THIS AFTERNOON, MAINLY ACROSS HIGHER
TERRAIN. BRIEF MVFR/IFR CONDITIONS AND MTN OBSCURATION IN
SHOWERS. SNOW LEVELS: 5.5-6.5 KFT MSL. SURFACE WINDS: W-N 5-15
KT WITH GUSTS TO 20-25 KT THIS AFTERNOON. BECOMING VARIABLE 5-10
KT OVERNIGHT. WINDS ALOFT AT 10KFT MSL: N 10-20 KT.
KBOI...VFR. SHOWERS OVER THE FOOTHILLS THIS AFTERNOON. SURFACE
WINDS: NW 10-20 KT WITH GUSTS UP 28 KT THIS AFTERNOON, BECOMING
SW-NW UP TO 8 KT OVERNIGHT.
BOI WATCHES/WARNINGS/ADVISORIES
ID...FROST ADVISORY FROM 4 AM TO 8 AM MDT TUESDAY FOR IDZ016.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
SHORT TERM...DG
LONG TERM....NF
AVIATION.....NF
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