547
FXUS65 KBOI 181028
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
328 AM MST TUE NOV 18 2025
SHORT TERM...TODAY THROUGH THURSDAY NIGHT
A LARGE UPPER
LEVEL LOW PRESSURE SYSTEM TO THE SOUTH AND A WEAK UPPER LEVEL
TROUGH TO THE NORTH TODAY WILL CONTINUE RELATIVELY QUIET WEATHER
ACROSS THE FORECAST AREA, WITH ONE EXCEPTION. DENSE FOG HAS
FORMED IN SEVERAL VALLEYS THIS MORNING AS A RESULT OF LOW
MOISTURE FROM YESTERDAY'S RAINFALL AND WEAK DIFFUSE FLOW ALOFT.
AREA WEBCAMS AND SATELLITE IMAGERY SHOW THE DENSEST FOG ACROSS
THE LOWER TREASURE VALLEY INTO THE UPPER WEISER BASIN, AND THIS
IS EXPECTED TO LAST THROUGH THE MORNING COMMUTE PERIOD.
TEMPERATURES REMAIN WELL ABOVE FREEZING, BUT VISIBILITIES ARE A
QUARTER MILE OR LESS, ESPECIALLY FROM ONTARIO THROUGH NAMPA.
LONG VALLEY AS WELL AS PART OF BAKER VALLEY ARE ALSO SEEING
PATCHY DENSE FOG. EASTERLY WINDS IN THE UPPER TREASURE VALLEY
HAVE KEPT FOG WEST OF BOISE, THOUGH IT IS POSSIBLE (50 PERCENT
CHANCE) IT DOES MOVE INTO BOISE LATER THIS MORNING. PLEASE ALLOW
EXTRA TIME THIS MORNING DURING THE COMMUTE.
FOG SHOULD LARGELY DISSIPATE BY THIS AFTERNOON ALONG WITH ANY
LOW CLOUDS. THE WEAK UPPER LEVEL TROUGH PASSAGE TODAY WILL BRING
A 20 TO 40 PERCENT CHANCE OF MOUNTAIN SNOW ABOVE 5000 TO 6000
FEET, WITH VALLEY RAIN IN BAKER COUNTY AND THE WEST CENTRAL
MOUNTAINS. TEMPERATURES WILL COOL SLIGHTLY FROM YESTERDAY BUT
REMAIN ABOUT 10 DEGREES ABOVE NORMAL IN THE LOWER VALLEY FOR
THIS TIME OF YEAR.
FOG LOOKS TO REDEVELOP AGAIN TONIGHT IN THE VALLEYS. THE LATEST
HIGH-RES RUNS THIS MORNING HAVE SHIFTED THE FOG DEVELOPMENT
EASTWARD THROUGH MUCH OF THE TREASURE VALLEY. ANOTHER DENSE FOG
ADVISORY MAY BE NEEDED TONIGHT. A 20 PERCENT CHANCE OF SHOWERS
ACROSS THE HIGHER TERRAIN WEDNESDAY AFTERNOON AS THE ANOTHER
WEAK TROUGH MOVES EAST ACROSS THE AREA. A WEAK SHORTWAVE RIDGE
FOLLOWS AS ANOTHER SPLIT TROUGH REACHES THE PACIFIC NORTHWEST
COAST. MUCH LIKE THE CURRENT SYSTEM, THE MAIN PARTS OF THIS
SYSTEM WILL BE SOUTH (CLOSED LOW) OR NORTH (OPEN TROUGH),
LEAVING THE FORECAST AREA BETWEEN FOR LOW CHANCES (15 TO 25
PERCENT) FOR PRECIPITATION ACROSS THE HIGHER TERRAIN.
TEMPERATURES WILL REMAIN 5 TO 10 DEGREES ABOVE NORMAL THROUGH
THE PERIOD.
LONG TERM...FRIDAY THROUGH TUESDAY
WITH THE UPPER-LEVEL LOW
MOVING DOWN THE CALIFORNIA COAST, UPPER-LEVEL FLOW OVER THE AREA
WILL BE LARGELY NEBULOUS. FOG LOOKS TO BE A REGULAR OCCURRENCE WITH
THIS WEAK PATTERN, ESPECIALLY IN VALLEY FLOORS. FLOW WILL BECOME
ZONAL SUNDAY THANKS IN PART TO AN UPPER-LEVEL RIDGE WELL OFF THE
COAST OF CALIFORNIA, HOWEVER IT WILL BE SHORT LIVED FROM A
DEVELOPING UPPER-LEVEL TROUGH IN THE GULF OF ALASKA. THIS QUICKLY
MOVES ONSHORE INTO THE PACIFIC NW LATE SUNDAY/EARLY MONDAY, WITH
LONG RANGE MODELS DISAGREEING ON TIMING AND INTENSITY. REGARDLESS,
WIDESPREAD POPS OF 20-40% CHANCES EXIST FROM EARLY MONDAY THROUGH
THE EXTENDED AS THIS TROUGH MAKES ITS WAY EAST. HIGHEST CHANCES OF
POPS WILL BE IN THE WEST-CENTRAL MOUNTAINS, WHERE SNOW LEVELS WILL
BE 3500-4500 FEET MSL BEHIND A COLD FRONT.
AVIATION
AREAS OF LIFR FOG ONGOING ACROSS THE TREASURE
VALLEY/NEAR KBKE TO LAST THROUGH LATE TUESDAY MORNING. CEILINGS TO
GRADUALLY RISE GOING INTO THE AFTERNOON HOURS, HOWEVER, THEY ARE
EXPECTED TO DROP AGAIN TO IFR/LIFR CONDITIONS AREAWIDE TUESDAY
NIGHT/WEDNESDAY MORNING FROM FOG/LOW STRATUS. WIDESPREAD MOUNTAIN
OBSCURATIONS. SURFACE WINDS: VARIABLE UNDER 10 KT. WINDS ALOFT AT
10KFT MSL: S-SW 5-15KT.
KBOI...FOG SLOWLY MOVING EAST/STATIONARY THROUGH THE TREASURE VALLEY
TUESDAY MORNING. LIFR CHANCES AT TERMINAL ARE 50%, BECOMING NEAR 0%
CHANCE AFTER 17Z. VFR THROUGH AFTERNOON INTO EARLY EVENING. LATE
TUESDAY EVENING/EARLY WEDNESDAY MORNING, LIFR CONDITIONS 40-60%
CHANCE FROM FOG/LOW STRATUS. SURFACE WINDS: VARIABLE 6 KT OR LESS.
BOI WATCHES/WARNINGS/ADVISORIES
ID...DENSE FOG ADVISORY UNTIL 10 AM MST THIS MORNING IDZ012-033.
OR...DENSE FOG ADVISORY UNTIL 10 AM MST /9 AM PST/ THIS MORNING
ORZ064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
SHORT TERM...JDS
LONG TERM....CH
AVIATION.....CH
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