Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 270345
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
845 PM MST WED NOV 26 2014

.DISCUSSION...EVENING SATELLITE IMAGERY SHOWS A COLD FRONT JUST OFF
THE NW COAST BUT THE FRONT WILL DISSIPATE BEFORE IT CAN GET HERE DUE
TO A BROAD UPPER RIDGE OVER THE INTERIOR WRN U.S.  DRY MILD WX WILL
CONTINUE IN OUR CWA THROUGH THANKSGIVING DAY ALTHOUGH SKIES WILL BE
MOSTLY CLOUDY...ESPECIALLY IN NRN ZONES.  A COLD UPPER TROUGH WILL
COME SOUTH THROUGH BC FRIDAY AND SATURDAY...AND OUR NRN ZONES WILL
DEFINITELY GET QUITE A BIT COLDER BY SUNDAY.  MODELS DIFFER ABOUT
WHETHER THE TROUGH WILL REACH OUR SRN ZONES...GFS SAYS NO...ECM SAYS
YES...BUT RECENT MODEL TRENDS SUPPORT THE COLDER ECM.  IF THE ECM
VERIFIES THEN A COLD FRONT WILL PASS THROUGH OUR SRN ZONES LATE
SATURDAY WITH GUSTY WINDS AND RAIN AND SNOW SHOWERS...CHANGING TO
SNOW SHOWERS SATURDAY EVENING.  AFTERNOON FORECAST FAVORED THE COLDER
ECM AND WE SEE NO REASON TO DISAGREE.

&&

.AVIATION...MVFR CONDITIONS IN FOG KMYL AND VICINITY.  OTHERWISE VFR
CONDITIONS WITH THICKENING AND LOWERING CLOUDS.  SLIGHT CHANCE OF
RAIN AND SNOW SHOWERS AND MOUNTAIN OBSCURATION SPREADING INTO BAKER
COUNTY AND THE WEST CENTRAL MOUNTAINS BY MORNING...INCREASING TO A
CHANCE THURSDAY MORNING AND SPREADING SOUTH TO A KBNO-KONO-KSUN
LINE.  SURFACE WINDS 10 KNOTS OR LESS.  WINDS ALOFT WILL BE WESTERLY
20 TO 30 KNOTS UP THROUGH 10K FEET MSL.

&&

.PREV DISCUSSION...
SHORT TERM...TONIGHT THROUGH FRIDAY...UPPER LEVEL RIDGE OVER THE
PACNW AND IDAHO BROUGHT MILD TEMPERATURES /59 AT BOISE SO FAR/ AND
CONSIDERABLE CLOUDINESS. THE UPPER RIDGE WILL FLATTEN THANKSGIVING
DAY AS A COLD UPPER LEVEL TROUGH ACROSS WEST CANADA PUSHES SOUTH.
IR SATELLITE IMAGERY SHOWS A DEEP UPPER LOW OVER THE SE PART OF
THE GULF OF AK. TO ITS SOUTH AND EAST WATER-VAPOR AND AIRCRAFT /
SATELLITE DERIVED WIND REPORTS INDICATE A BROAD AREA OF STRONG MID-
LEVEL WINDS AND RATHER MOIST CONDITIONS. THIS MOISTURE WILL SHIFT
EAST AND LOOKS TO AFFECT NORTH CENTRAL TO NE OREGON AND CENTRAL
IDAHO. THE CANADIAN TROUGH DROPPING SOUTH WILL INCREASE MID-LEVEL
WINDS FOR ENHANCED OROGRAPHIC LIFT. DEEPER MOISTURE AND STRONG
LIFT ARE POISED UPSTREAM TO THE WEST WHILE MUCH COLDER CONDITIONS
LOOM TO THE NORTH.

LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY EVENING...AS FRIDAY
NIGHT WEARS ON...THE AREA WILL CONTINUE TO BE IN A MOIST SOUTHWEST
FLOW WHICH WILL CONTINUE THE UPSLOPE PRECIPITATION FOR THE WEST
CENTRAL MOUNTAINS THROUGH EARLY SATURDAY. AT THE SAME TIME...A
COLD FRONT WILL BEGIN MOVING INTO THE AREA FROM NORTHWEST TO
SOUTHEAST. CURRENT FORECAST TIMES THE COLD FRONT TO BE NEAR A LINE
FROM BURNS TO BAKER AROUND NOON SATURDAY AND BE PASSING THROUGH THE
MAGIC VALLEY BY SATURDAY NIGHT. SNOW LEVELS WILL BE AROUND 5000 TO
6000 FT MSL AHEAD OF THE FRONT AND DROP TO VALLEY FLOORS TOWARDS THE
END OF POTENTIAL PRECIPITATION...SO MAJOR SNOW ACCUMULATIONS WILL
LIKELY EXIST ONLY IN THE WEST CENTRAL MOUNTAINS. CLEARING WILL FOLLOW
THE FRONT AND TEMPERATURES WILL DROP...POSSIBLY 10-15 DEGREES...FROM
SATURDAY TO SUNDAY. WHILE THIS COLD FRONT IS WORKING ITS WAY THROUGH
THE AREA...A CUTOFF LOW WILL POSITION ITSELF OFF THE COAST OF NORTHERN
CALIFORNIA.  MODELS ARE IN DECENT AGREEMENT THAT THIS CUTOFF LOW WILL
SEND A WARM FRONT THROUGH OUR AREA FROM SOUTH TO NORTH LATE SUNDAY
INTO MONDAY. HOWEVER...THE GFS BRINGS THIS FRONT IN ABOUT 12 HOURS
SOONER THAN THE ECMWF...SO UNCERTAINTY EXISTS FOR MANY VARIABLES.
FOR TUESDAY AND WEDNESDAY...THE AREA LOOKS TO REMAIN IN A FAIRLY
ACTIVE PATTERN AS THAT CUTOFF LOW BEGINS TO SLOWLY MOVE EAST...SO
FORECAST IS CLOSE TO CLIMO AS TIMING IS STILL UNCLEAR.

&&

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

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...LC
AVIATION.....JA
PREV SHORT TERM...VM
PREV LONG TERM....EP/WH


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