338
FXUS65 KBOI 181938
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
138 PM MDT TUE AUG 18 2026
KEY MESSAGES
- TEMPERATURES WARMING THROUGH THE END OF THE WEEK WITH LOWER
ELEVATIONS AROUND 100 DEGREES THURSDAY AND FRIDAY.
- INCREASED CHANCE OF SHOWERS AND THUNDERSTORMS OVER HIGHER
TERRAIN THIS WEEKEND AND INTO NEXT WEEK.
SHORT TERM /THROUGH THURSDAY NIGHT/
A RIDGE OF HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE REGION
THROUGH THE WORK WEEK, BRINGING A STEADY WARMING AND DRYING
TREND. CLOUDS HAVE DECREASED ACROSS MOST OF THE REGION TODAY,
WITH A SCATTERED CUMULUS BUILD UPS OVER HIGH TERRAIN IN CENTRAL
IDAHO AND NEAR THE ID-NV BORDER. A FEW VIRGA SHOWERS WILL
CONTINUE NEAR THE ID-NV BORDER THROUGH THE EVENING, OTHERWISE
MOSTLY CLEAR AND WARM CONDITIONS WILL CONTINUE. TEMPERATURES
WILL INCREASE TO ABOUT 8-12 DEGREES ABOVE NORMAL BY THURSDAY,
WITH LOWER ELEVATIONS REACHING NEAR OR SLIGHTLY ABOVE 100F. A
PUSH OF MONSOON MOISTURE WILL PRIMARILY STAY TO OUR SOUTH ON
THURSDAY AFTERNOON, ALTHOUGH THERE IS A LOW CHANCE (10-20%) OF
SHOWERS AND THUNDERSTORMS OVER THE MAGIC VALLEY LATE THURSDAY.
RAINFALL ACCUMULATIONS WILL BE MINIMAL WITH ANY THUNDERSTORMS
THAT FORM, SO GUSTY OUTFLOW WINDS AND LIGHTNING WOULD BE THE
PRIMARY CONCERN.
LONG TERM /FRIDAY THROUGH TUESDAY/
SOUTHERLY FLOW ALOFT BROUGHT ABOUT BY THE OFFSHORE PACIFIC LOW
PRESSURE SYSTEM AND THE FOUR CORNERS UPPER-LEVEL RIDGE WILL KEEP
TEMPERATURES HOT ON FRIDAY. ANOTHER DAY OF 100 DEGREE HEAT TO LOWER
ELEVATIONS IS EXPECTED. THE UPPER-LEVEL TROUGH WILL MOVE INLAND LATE
FRIDAY INTO SATURDAY, MOVING THROUGH THE INTERIOR NW ON SATURDAY.
COOLING ALOFT AND INCREASED MOISTURE WILL SUPPORT A 20-30% CHANCE OF
SHOWERS AND THUNDERSTORMS ACROSS HIGHER TERRAIN OF E-CENTRAL OREGON
AND SW IDAHO FRIDAY, SHIFTING TO MOSTLY SW IDAHO FOR SATURDAY AND
SUNDAY. TEMPERATURES WILL BE COOLER BEHIND THIS DISTURBANCE,
LOWERING TO NEAR-NORMAL SATURDAY AND SUNDAY. LONG-RANGE MODELS HINT
AT THE FOUR CORNERS RIDGE REBUILDING OVER THE AREA EARLY NEXT WEEK
WITH TEMPERATURES WARMING AGAIN. THE REAL QUESTION WILL BE MOISTURE
EARLY NEXT WEEK; SOME MODELS SHOW A STRONG SURGE WITH HIGH
PRECIPITATION CHANCES AND QPF TOTALS, WHILE OTHERS SHOW A MORE
LIMITED SCENARIO. THE CURRENT FORECAST SHOWS SOMEWHERE IN THE
MIDDLE, WITH A 10-30% CHANCE OF SHOWERS/STORMS OVER SW IDAHO.
AVIATION /18Z TUESDAY THROUGH WEDNESDAY/
ISSUED 1120 AM MDT TUE AUG 18 2026
VFR WITH MID-HIGH CLOUDS ACROSS FAR SE OREGON AND SOUTHERN IDAHO.
SCATTERED AFTERNOON CUMULUS IN MTNS WITH ISOLATED
SHOWERS/THUNDERSTORMS NORTH AND EAST OF KMYL AND HIGHER TERRAIN
SOUTH OF KTWF. SURFACE WINDS: W-NW 5-15 KT. WINDS ALOFT AT 10KFT
MSL: W-SW 5-15 KT, BECOMING W 5-20 KT BY 00Z/WED.
KBOI...VFR WITH SCATTERED HIGH CLOUDS THROUGH THIS MORNING.
LIGHT SURFACE WINDS WITH VARIABLE DIRECTION BECOMING NW IN THE
AFTERNOON.
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...SA
LONG TERM....CH
AVIATION.....CH
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