105
FXUS65 KBOI 191705
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1005 AM MST TUE NOV 19 2024
DISCUSSION
UPDATED THE WINDS AND WIND GUSTS FOR TONIGHT AND
WEDNESDAY MORNING. A FEW HIGH RESOLUTION MODELS HAD GUSTS ABOVE
THE NBM DETERMINISTIC AND GENERAL MODEL CONSENSUS. RETURN
INTERVALS FOR WIND SPEEDS WERE GENERALLY 1 DAY IN EVERY 5 YEARS,
AND GIVEN WIND GUSTS WERE ALREADY FAIRLY HIGH A WIND ADVISORY
HAS BEEN ISSUED. IN HARNEY COUNTY, ESPECIALLY IN THE SOUTH,
WIDESPREAD GUSTS OF 35-45 MPH ARE EXPECTED WITH PEAK GUSTS OF UP
TO 50 MPH. IN BAKER COUNTY AND THE LOWER TREASURE VALLEY
INCLUDING ONTARIO, THE MAIN WIND THREAT IS OVER HIGH TERRAIN AND
THE I-84 CORRIDOR. ALTHOUGH WINDS HERE SHOULD PEAK AT 45 MPH,
JUST A LITTLE "WEAKER" THAN HARNEY COUNTY.
STILL ON TRACK FOR A FAIRLY WET FORECAST, WITH A WEAK UPPER
TROUGH TODAY BRINGING SNOW ACROSS NORTHERN AREAS, AND A QUICKLY
INTENSIFYING PACIFIC LOW ON TRACK TO BRING AN ATMOSPHERIC RIVER
THROUGH OUR AREA. NO UPDATES WITH THIS SYSTEM, THE BULK OF
PRECIPITATION WILL STILL OCCUR ACROSS THE NORTHERN AREAS THANKS
TO OROGRAPHIC EFFECT. THERE IS SOME SKEPTICISM FOR OUR RAINFALL
FORECAST IN THE TREASURE VALLEY AS SOUTHWEST FLOW ALOFT MAY
LEAVE US SHADOWED. OVERALL IT SEEMS OUR CURRENT FORECAST AND
PREVIOUS DISCUSSION STILL HANDLE IT WELL ENOUGH. A WINTER
WEATHER ADVISORY FOR THE BOISE MTNS WILL LIKELY BE ISSUED WITH
THE AFTERNOON FORECAST. THE HWY 21 CORRIDOR THROUGH MORES CREEK
TO BANNER SUMMIT IS VERY LIKELY TO RECEIVE OVER 4 INCHES OF SNOW
WEDNESDAY THROUGH THURSDAY, WITH THE CURRENT FORECAST BEING
GENERALLY 8-16 INCHES DEPENDING ON ELEVATION.
AVIATION
VFR TODAY, WITH DETERIORATING CONDITIONS
OVERNIGHT INTO WEDNESDAY, ESPECIALLY FOR EASTERN OREGON AND KMYL. A
LOW PRESSURE SYSTEM WILL GENERATE A PROLONGED PERIOD OF UNSETTLED
WEATHER, WIDESPREAD MVFR/IFR CONDITIONS, AND TERRAIN OBSCURATION
WEDNESDAY THROUGH SATURDAY. LOW LEVEL WIND SHEER LIKELY FOR MANY
SITES BEGINNING EARLY WEDNESDAY. SURFACE WINDS GENERALLY SE LESS
THAN 15 KTS, INCREASING TO SE 15-25 KTS AFTER 2006Z. WINDS ALOFT SW
30-40 KT.
KBOI
VFR, WITH SE WINDS LESS THAN 15 KTS, INCREASING OVERNIGHT
(2006Z) TO 15-25 KTS WITH GUSTS TO 30 KT. ACTIVE WEATHER WITH
VISIBILITY AND CEILING RESTRICTIONS BEGINNING EARLY WEDNESDAY AND
LINGERING THROUGH SATURDAY. LOW LEVEL WIND SHEER LIKELY OVERNIGHT
WITH INCREASING SE WINDS.
PREV DISCUSSION
SHORT TERM...TODAY THROUGH THURSDAY NIGHT...A WEAK UPPER TROUGH
WILL BRING A 30 TO 50 PERCENT CHANCE OF SNOW ACROSS NORTHERN
AREAS (MAINLY BAKER COUNTY TO THE WEST CENTRAL ID MOUNTAINS)
THIS MORNING. LITTLE SNOWFALL ACCUMULATIONS ARE EXPECTED. THE
CHANCES FOR SNOW DECREASE THIS AFTERNOON AS A SHORT-WAVE UPPER
RIDGE BUILDS IN FROM THE WEST. OTHERWISE, DRY CONDITIONS PREVAIL
TODAY.
A STRONG STORM SYSTEM DEVELOPS OFF THE PACNW COAST WHICH WILL
ENHANCE THE WINDS ACROSS THE REGION LATER TODAY. WINDS CONTINUE
TO INCREASE TONIGHT AS A SURFACE LOW OFF THE COAST INTENSIFIES.
SOUTH TO SOUTHEAST WINDS OF 15 TO 25 MPH WITH HIGHER GUSTS WILL
BE COMMON. THE WINDS DIMINISH SOMEWHAT LATE WEDNESDAY AS THE
LOW MOVES FURTHER OFFSHORE, BUT LOCALLY BREEZY CONDITIONS WILL
PERSIST THROUGH THURSDAY.
THE MAIN IMPACT WITH THE STORM SYSTEM WILL BE ASSOCIATED WITH
A LONG FETCH OF MOISTURE THAT EXTENDS WELL INTO THE PACIFIC,
OTHERWISE KNOWN AS AN ATMOSPHERIC RIVER. SOUTHWEST FLOW ALOFT
AHEAD OFF THE STORM SYSTEM OFF THE COAST WILL DRIVE THE MOISTURE
INLAND AND IS EXPECTED TO REACH OUR AREA TONIGHT, BRINGING
PERIODS OF PRECIPITATION THROUGH THURSDAY NIGHT. MODELS ARE IN
AGREEMENT THAT THE BULK OF THE PRECIPITATION WILL BE GENERALLY
NORTH OF A BURNS-BOISE-FAIRFIELD LINE, WHERE LIQUID TOTALS
THROUGH THE PERIOD LIKELY (>60 PERCENT CHANCE) EXCEED AN INCH
WITH LOCAL AMOUNTS OF UP TO TWO INCHES. SNOW LEVELS START OFF
NEAR VALLEY FLOORS, BUT STEADILY RISE THROUGH THE PERIOD AS
WARMER AIR ARRIVES WITHIN THE SOUTHWEST FLOW. MOUNTAIN VALLEYS
IN THE NORTH COULD RECEIVE SEVERAL INCHES OF SNOWFALL BEFORE
CHANGING TO RAIN ON THURSDAY, WHILE THE HIGHER MOUNTAINS COULD
SEE 1 TO 2 FEET OF SNOW. TEMPERATURES TREND A FEW DEGREES WARMER
EACH DAY, FROM SLIGHTLY BELOW NORMAL TODAY, TO NEAR NORMAL ON
WEDNESDAY, AND FINALLY SLIGHTLY ABOVE NORMAL ON THURSDAY.
LONG TERM...FRIDAY THROUGH TUESDAY...DEEP MOISTURE IN
SOUTHWEST FLOW ALOFT WILL CONTINUE ON FRIDAY, BRINGING
PRECIPITATION AND BREEZY/WINDY CONDITIONS TO THE AREA.
PRECIPITABLE WATER VALUES WILL BE HIGH, AROUND THE 90TH
PERCENTILE. THE HIGHEST CHANCES FOR PRECIPITATION WILL BE IN
NORTHEAST OR AND WEST-CENTRAL ID, WITH LOWER CHANCES CLOSER TO
THE NV BORDER. TEMPERATURES WILL BE MILD AT ROUGHLY 10 DEGREES
ABOVE NORMAL, WITH SNOW LEVELS AROUND 7000-8000 FEET MSL. A FEW
INCHES OF SNOW CAN BE ANTICIPATED ON HIGH ELEVATIONS FRIDAY,
WHEREAS HEFTY RAINFALL TOTALS ARE EXPECTED FOR MOST MID AND LOW
ELEVATIONS. MODELS INDICATE A TROUGH AND ITS ASSOCIATED COLD
FRONT WILL FINALLY ARRIVE SATURDAY, WITH SHOWERY AND BREEZY
CONDITIONS CONTINUING OVER THE WEEKEND. SNOW LEVELS WILL LOWER
TO 3500-5000 FT MSL BEHIND THE FRONT, AND MAX TEMPERATURES WILL
LOWER TO NEAR/SLIGHTLY BELOW NORMAL FOR SAT/SUN. A SECONDARY
WAVE IS FORECAST TO ARRIVE SOMETIME MONDAY OR TUESDAY,
ACCOMPANIED BY A 40-60% CHANCE OF SHOWERS.
BOI WATCHES/WARNINGS/ADVISORIES
ID...NONE.
OR...WIND ADVISORY FROM 8 PM MST /7 PM PST/ THIS EVENING TO 11 AM
MST /10 AM PST/ WEDNESDAY ORZ061-062-064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.TWITTER.COM/NWSBOISE
DISCUSSION...JM
AVIATION.....MC
SHORT TERM...BW
LONG TERM....SH
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