Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 280330
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
830 PM MST THU NOV 27 2014

.DISCUSSION...CURRENTLY...LONG WAVE RIDGE AND MILD WX OVER THE WRN
U.S. AND A STRONG COLD SHORT WAVE TROUGH OVER NRN BC.  SATELLITE
SHOWS A WEAKENING FRONTAL BAND /WITH LIGHT PCPN/ QUASI-STATIONARY
ACROSS OUR NRN ZONES.  THE WRN U.S. RIDGE WILL BE FLATTENED AND
PUSHED SOUTH LATE FRIDAY NIGHT THROUGH SATURDAY AS THE BC TROUGH
COMES IN.  STRONG FRONTOGENESIS WILL OCCUR LATE FRIDAY FROM NWRN
MONTANA THROUGH NRN OREGON TO AROUND 43/130 IN THE PACIFIC.  PACIFIC
MOISTURE STILL COMING IN ABOVE THE FRONTAL ZONE WILL DEVELOP
WIDESPREAD RAIN AND SNOW...CHANGING TO SNOW SHOWERS BEHIND FROPA.
THE FRONT WILL REACH OUR NRN ZONES EARLY SATURDAY MORNING AND SRN
ZONES SATURDAY AFTERNOON.  SEVERAL INCHES NEW SNOW WILL FALL IN
MOUNTAIN AREAS BELOW 6000 FEET MSL...LIKE SUMPTER/OR AND MCCALL AND
IDAHO CITY IN IDAHO.  HIGHER MOUNTAINS IN IDAHO CAN EXPECT 12-18
INCHES.  LOWER VALLEYS INCLUDING THE SNAKE BASIN WILL GET LITTLE IF
ANY NEW SNOW.  BUT RAPID FREEZING ON THE WET ROADS IS EXPECTED
SATURDAY NIGHT AND TRAVEL SUNDAY MAY BE DIFFICULT DUE TO LOCAL ICE
ON VALLEY ROADS AND NEW SNOW ON MOUNTAIN ROADS.  TEMPS WILL BE MUCH
COLDER SUNDAY BEHIND THE ARCTIC FRONT...ESPECIALLY OVER NEW SNOW
COVER.  NO UPDATES.

&&

.AVIATION...MOSTLY VFR CONDITIONS WITH MID-HIGH CLOUDS. OCCASIONAL
MVFR CONDITIONS AND MOUNTAIN OBSCURATION IN WEST CENTRAL MOUNTAINS
FROM PASSING SHOWERS. SURFACE WINDS GENERALLY LIGHT. WINDS ALOFT
NEAR 10K FT MSL...WEST AT 35 TO 45 KTS.

WEEKEND OUTLOOK...FRIDAY NIGHT THROUGH SATURDAY MORNING MVFR/IFR
SNOW WILL CONTINUE ACROSS BAKER COUNTY OREGON AND THE CENTRAL IDAHO
MOUNTAINS. OTHERWISE EXPECT VFR CONDITIONS FOR MOST OF SOUTHEAST
OREGON AND SOUTHWEST IDAHO. SATURDAY AFTERNOON VALLEY RAIN AND
MOUNTAIN SNOW WILL SPREAD SOUTH TO THE NEVADA LINE AND CONTINUE
ACROSS THE ENTIRE AREA THROUGH SATURDAY NIGHT...WITH SNOW LEVELS
LOWERING TO THE VALLEY FLOORS. SUNDAY DRIER AIR MOVING DOWN FROM THE
NORTH WILL BRING IMPROVING CONDITIONS...WITH MAINLY VFR.

&&

.PREV DISCUSSION...
SHORT TERM...TONIGHT THROUGH SATURDAY...MILD AND MOIST SOUTHWEST
FLOW ASSOCIATED WITH AN UPPER RIDGE OVER THE PAC NW WILL GIVE WAY TO
AN APPROACHING ARCTIC FRONT ON SATURDAY. SE OREGON AND SW IDAHO WILL
REMAIN IN THE WARM SECTOR INTO SATURDAY WITH TEMPERATURES 10-15
DEGREES ABOVE NORMAL MOST LOCATIONS /THOUGH MAGIC VALLEY WILL SEE
TEMPS REACH 60 AGAIN ON FRIDAY/. MOISTURE IN THE SOUTHWEST FLOW WILL
CONCENTRATE OVER EAST-CENTRAL OREGON AND MTNS OF SW IDAHO TONIGHT...
SHIFTING SOUTH THROUGH THE DAY FRIDAY. SNOW LEVELS WILL REMAIN ABOVE
6K FEET THROUGH TONIGHT...GRADUALLY DROPPING FRIDAY AND FRIDAY NIGHT
IN RESPONSE TO COOLING ALOFT. PRECIPITATION AMOUNTS WILL RAMP UP
STARTING FRIDAY NIGHT AS DYNAMICS FROM UPPER TROUGH INTERACT WITH
MOISTURE STREAMING IN FROM THE PACIFIC. THROUGH FRIDAY THE SNAKE
RIVER VALLEY WILL REMAIN MOSTLY DRY /ONLY SLIGHT CHANCE OF SHOWERS/
WITH INCREASING CHANCES OF PCPN FRIDAY NIGHT AND SATURDAY. SOME
TIMING DIFFERENCES IN ARRIVAL OF THE ARCTIC FRONT...BUT BY SATURDAY
AFTERNOON ALL SOLUTIONS SHOW THE FRONT PUSHING THROUGH SE OREGON AND
SW IDAHO. AT THIS TIME HIGHLIGHTS ARE UNNECESSARY AS FORECAST 10+
INCH SNOW TOTALS WILL BE ABOVE 6K FEET MSL.

LONG TERM...SATURDAY NIGHT THROUGH THURSDAY...MODELS AGREE ON ARCTIC
AIR RE-INVADING THE NORTHERN INTERMOUNTAIN REGION SATURDAY NIGHT
BENEATH AN UPPER LEVEL TROUGH IN NORTHERLY FLOW ALOFT.  WIDESPREAD
PRECIPITATION IS EXPECTED SATURDAY NIGHT AS THE ARCTIC AIR PUSHES
SOUTH BENEATH THE MOIST PACIFIC AIR. PRECIPITATION SHOULD BEGIN AS
RAIN IN THE VALLEYS SATURDAY EVENING CHANGING TO SNOW AT ALL
ELEVATIONS OVERNIGHT. ON SUNDAY MUCH DRIER COLD AIR MOVING DOWN FROM
B.C. WILL KEEP MOST OF THE PRECIPITATION ALONG THE NEVADA BORDER.
TEMPERATURES SUNDAY AND MONDAY WILL BE 10 TO 15 DEGREES BELOW
NORMAL. THERE IS UNCERTAINTY REGARDING TIMING OF THE RETURNING
PACIFIC MOISTURE. BOTH THE GFS AND ECMWF HAVE BEEN TRENDING LESS
PROGRESSIVE...ESPECIALLY THE ECMWF...WHICH IS PREFERRED. BASED ON
THIS SLOWER TIMING...THE BEST CHANCE OF PRECIPITATION NOW APPEARS TO
BE TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. TEMPERATURES WILL SLOWLY
MODERATE TO AROUND 5 DEGREES BELOW NORMAL ON TUESDAY AND NEAR NORMAL
WEDNESDAY THROUGH THURSDAY.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...LC
AVIATION.....EP/JT
PREV SHORT TERM...DG
PREV LONG TERM....JT


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