305
FXUS65 KBOI 171726
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1026 AM MST SUN NOV 17 2024
DISCUSSION
WARM FRONT CONTINUES TO MOVE ACROSS EASTERN OR AND
SOUTHWEST ID THIS MORNING. SNOW LEVELS HAVE RISEN TO AROUND
5000 FEET ACROSS SOUTHEAST OR, WITH SNOW LEVELS PRESENTLY AT
THE VALLEY FLOORS IN SOUTHWEST ID. DRY SOUTHEAST WINDS IN THE
TREASURE VALLEY HAVE DELAYED PRECIPITATION ONSET, AND HELPED
PRECIPITATION START OUT AS SNOW, BUT WILL QUICKLY CHANGEOVER TO
RAIN BY MIDDAY. TEMPERATURES CONTINUE TO WARM IN THE LOWER
ELEVATIONS, WITH RAIN BELOW 4500-6500FT THIS AFTERNOON. SNOW
LEVELS WILL BE SLOW TO RISE IN BAKER COUNTY, THE WEST CENTRAL ID
MOUNTAINS, AND THE WEISER RIVER BASIN WITH SNOW LEVELS
3500-4500FT THIS AFTERNOON. SURFACE WINDS WILL INCREASE TODAY
AHEAD OF THE COLD FRONT LATE THIS AFTERNOON. THEN THE COLD FRONT
WILL MOVE ACROSS EASTERN OR THIS EVENING, AROUND 6PM PST IN
BAKER CITY AND BURNS, AND THROUGH THE BOISE METRO AROUND 10PM
MST, AND TWIN FALLS AROUND 1AM MST. WOULD NOT BE SURPRISED TO
SEE THUNDERSHOWERS ALONG THE COLD FRONT LATE THIS EVENING. SNOW
LEVELS FALL TO THE VALLEY FLOORS BEHIND THE FRONT, BUT
PRECIPITATION QUICKLY TAPERS OFF AS DRIER AND COOLER AIR MOVES
INTO THE REGION. THE EASTERN OR BASINS AND THE SNAKE BASIN
BELOW 4000 FEET WILL SEE A DUSTING OF SNOW BEHIND THE COLD
FRONT, WITH 1 TO 3 INCHES OF SNOW IN THE WEISER BASIN, 3 TO 5
INCHES IN THE LONG VALLEY AND OWYHEE MOUNTAINS, AND 6 TO 10
INCHES OF SNOW ABOVE 6500 FEET MSL. THEN THE FORECAST TURNS TO
THE NEXT SYSTEM ON TUESDAY AND WEDNESDAY. MODELS CURRENTLY HAVE
A TROUGH GAINING RECORD BREAKING STRENGTH (945-955 MILLIBARS)
OFF THE PACIFIC NW COAST ON TUESDAY AND WEDNESDAY THAT WILL NEED
TO BE MONITORED. CURRENT FORECAST ON TRACK WITH NO UPDATES.
AVIATION
WIDESPREAD RAIN/SNOW MOVING NW TO SE THROUGH EARLY
MONDAY. MOSTLY MVFR TO LIFR IN PRECIP/LOW CEILINGS. RISING SNOW
LEVELS TODAY, THEN LOWERING TO VALLEY FLOORS BY EARLY MON AFTER A
COLD FRONT MOVES THROUGH TONIGHT. MOUNTAINS OBSCURED. SURFACE WINDS:
SE-SW 5-15 KT, INCREASING TO 10-20 KT WITH GUSTS 25-35 KT THIS
AFTERNOON, THEN W-NW 10-20 KT WITH GUSTS 25-35 KT THIS EVENING AS A
COLD FRONT PASSES. WINDS ALOFT AT 10KFT MSL: W TO SW 25-45 KT.
KBOI...CEILINGS MVFR THROUGH AT LEAST 18/09Z. LIGHT SNOW THIS
MORNING, CHANGING TO RAIN AROUND 18Z. STRONG COLD FRONT AROUND
18/06Z WILL BRING SNOW OR MIX MON/06Z-09Z WITH BRIEF IFR POSSIBLE,
THEN PRECIPITATION ENDING AND BECOMING VFR. SURFACE WINDS: SE 10-20
KT WITH GUSTS 25-35 KT. SHIFT TO NW 10-15 KT GUSTS 25-30 KT AROUND
MON/06Z.
PREV DISCUSSION
SHORT TERM...TODAY THROUGH TUESDAY NIGHT...WARM FRONT
CURRENTLY IN EASTERN OREGON WILL PASS THROUGH WESTERN IDAHO
THIS MORNING THROUGH EARLY AFTERNOON WITH A RAPID RISE IN SNOW
LEVEL. SNOW WILL CHANGE TO RAIN AS HIGH AS 6000 FEET MSL NORTH
TO 7000 FEET MSL SOUTH. COLDER WIND-PROTECTED VALLEYS IN HARNEY
AND MALHEUR COUNTIES, AND IN THE OWYHEE MOUNTAINS, WILL HAVE
A SLIGHT CHANCE OF FREEZING RAIN DURING THE CHANGEOVER. THE
STORM'S COLD FRONT WILL PASS THROUGH EASTERN OREGON EARLY
THIS EVENING, WESTERN IDAHO SHORTLY BEFORE MIDNIGHT, AND SOUTH-
CENTRAL IDAHO AFTER MIDNIGHT. WINDS WILL SHIFT TO GUSTY
NORTHWEST BUT NOT STRONG ENOUGH FOR A WIND ADVISORY. SNOW LEVEL
WILL LOWER RAPIDLY BEHIND THE FRONT, DOWN TO VALLEY FLOORS BY
SUNRISE, BUT LITTLE IF ANY ACCUMULATION IS EXPECTED IN THE
SNAKE BASIN. NORTHERN MOUNTAINS WILL RECEIVE 6 TO 12 INCHES NEW
SNOW TODAY THROUGH MONDAY NIGHT, BUT ONLY 4 TO 7 INCHES AT THE
5000 FOOT LEVEL. TOTAL LIQUID EQUIVALENT THROUGH MONDAY NIGHT
WILL BE .75 TO 1.30 INCH IN THE IDAHO MOUNTAINS NORTH OF THE
SNAKE BASIN, .25 TO .75 INCH IN BAKER COUNTY, AND GENERALLY .15
TO .30 INCH IN SOUTHERN AREAS, EXCEPT UP TO .50 INCH IN THE
SOUTHERN MOUNTAINS. AFTER DRYING TUESDAY THE NEXT NORTH PACIFIC
WARM FRONT WILL SPREAD MORE PCPN ACROSS EASTERN OREGON TUESDAY
NIGHT.
LONG TERM...WEDNESDAY THROUGH SUNDAY...AN ATMOSPHERIC RIVER
WILL ARRIVE WEDNESDAY, SPREADING A SIGNIFICANT PLUME OF
MOISTURE INTO MUCH OF EAST OREGON AND WEST-CENTRAL IDAHO THROUGH
FRIDAY. PRECIPITABLE WATER VALUES ARE FORECAST TO REACH ABOVE
THE 90TH PERCENTILE (HIGH). TEMPERATURES WILL TREND WARMER EACH
DAY, PEAKING AROUND 10 DEGREES ABOVE NORMAL FRIDAY. THE LOWER
SNOW LEVELS ON WEDNESDAY WILL RAPIDLY INCREASE TO ABOVE 7000 FT
MSL THU/FRI. AS A RESULT, MOUNTAINS ARE EXPECTED TO SEE SEVERAL
INCHES OF SNOW ACCUMULATION WEDNESDAY, THEN NOTABLY LOWER
AMOUNTS AS THE MID ELEVATIONS TRANSITION TO RAIN, AND SNOW
RATIOS DECREASE FOR THE REMAINING HIGH ELEVATIONS. SOUTHEAST
TO SOUTHWEST WINDS WILL ALSO INCREASE AND CREATE BREEZY TO
WINDY CONDITIONS WED THROUGH FRI, ESPECIALLY FOR MOUNTAIN
RIDGES AND THE WESTERN SNAKE PLAIN. SOME MODEL GUIDANCE
CONTINUES A MOIST, WEST-SOUTHWEST FLOW FOR THE WEEKEND,
EXPANDING THE PRECIPITATION CHANCES ACROSS THE REST OF
SOUTHEAST OREGON AND SOUTHWEST IDAHO BOTH SAT/SUN. SNOW LEVELS
WILL LOWER SLIGHTLY TO 4500-5500 FT MSL BY SUNDAY AS A COLD
FRONT ARRIVES SOMETIME SATURDAY NIGHT. THIS COLD FRONT WILL
STRENGTHEN THE SURFACE PRESSURE GRADIENT, RESULTING IN WINDY
CONDITIONS AHEAD AND BEHIND THE FRONT.
BOI WATCHES/WARNINGS/ADVISORIES
ID...NONE.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.TWITTER.COM/NWSBOISE
DISCUSSION...KA
AVIATION.....SP
SHORT TERM...LC
LONG TERM....SH
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