Area Forecast Discussion
Issued by NWS Boise, ID

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000
FXUS65 KBOI 201536
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
936 AM MDT MON OCT 20 2014

.DISCUSSION...LARGE UPPER LEVEL STORM OFF THE COAST THIS MORNING
WILL MOVE EAST OVERNIGHT AND BRING A STRONG COLD FRONT TO THE
REGION LATE TONIGHT AND TOMORROW MORNING. TEMPS STILL SET TO BE
10-15 DEGREES ABOVE NORMAL TODAY...FALLING AROUND 20 DEGREES TO
BECOME 5-10 DEGREES BELOW NORMAL TOMORROW. RAINFALL WILL ACCOMPANY
THE FRONT...WITH AMOUNTS OF NEAR A QUARTER INCH IN THE VALLEY AND
A HALF TO ONE INCH IN THE MOUNTAINS. FORECAST WINDS FOR THIS
AFTERNOON HAVE BEEN INCREASED SLIGHTLY. UPDATE OUT BY 1030 AM MDT.

&&

.AVIATION...VFR TODAY. MVFR CIGS WILL DEVELOP OVERNIGHT AND SPREAD
WEST TO EAST. ISOLATED IFR CIGS TOMORROW IN SHOWERS. SFC WINDS
SOUTHEAST THROUGH SOUTHWEST TODAY INTO TONIGHT 10-20 KTS WITH
GUSTS TO 25 KTS. A COLD FRONT WILL MOVE THROUGH SE OREGON TONIGHT
AND SW IDAHO TOMORROW BY NOON...SWITCHING WINDS TO WEST TO
NORTHWEST. THUNDERSTORMS ARE POSSIBLE THIS EVENING IN SE OREGON
ESPECIALLY NEAR KBNO AND KBKE. WINDS ALOFT WILL BE SW 20-25 KTS
TODAY INTO TONIGHT...BECOMING WEST 20-30 KTS TOMORROW.

&&

.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH TUESDAY...BROAD UPPER LEVEL TROUGH OFF
THE PACIFIC NORTHWEST COAST SLOWLY BEGINNING TO MOVE INLAND THIS
MORNING. A VIGOROUS SHORTWAVE NEAR 135W AND 40N WILL MOVE INTO
NORTHERN CA AND NORTHEASTWARD THROUGH THE GREAT BASIN INTO
SOUTHERN IDAHO BY TUESDAY AFTERNOON. THIS SHORTWAVE WILL BECOME
NEGATIVELY TILTED AND MOVE ACROSS SOUTHEAST OREGON AND SOUTHWEST
IDAHO TUESDAY. A SLIGHT CHANCE OF THUNDERSTORMS IN CENTRAL OREGON
AS THERE ARE NEGATIVE LI VALUES AND BUFR CAPE VALUES OF AROUND
500J/KG NEAR BURNS. WINDS THIS AFTERNOON WILL BECOME GUSTY FROM
THE SOUTHWEST IN SOUTH CENTRAL OREGON AHEAD OF THIS SYSTEM AS
WINDS ALOFT ARE QUITE STRONG FROM THE SOUTHWEST. EXPECT INCREASING
HIGH CLOUDS LATER THIS MORNING WITH PRECIPITATION CHANCES
INCREASING LATE THIS EVENING INTO THE OVERNIGHT HOURS. GOOD
AGREEMENT WITH THE MODELS AND A SWATH OF IMPRESSIVE QPF AMOUNTS UP
TO 0.50-0.75 INCHES WITH THIS SYSTEM CAN BE EXPECTED IN THE
CENTRAL IDAHO MOUNTAINS WITH MOST VALLEY LOCATIONS RECEIVING
UP TO 0.25 INCHES IN IDAHO. SNOW LEVELS WILL LOWER TO 7000 FEET
MSL TUESDAY AFTERNOON BEFORE THE PRECIPITATION SHUTS OFF LATE
TUESDAY. SOME OF THE HIGHER PEAKS COULD SEE A COUPLE INCHES OF
SNOW WITH THIS SYSTEM. THERE IS A POTENTIAL FOR GUSTY WINDS WITH
THE COLD FRONTAL PASSAGE IN THE TREASURE AND MAGIC VALLEY BUT
ELECTED NOT TO INTRODUCE THEM INTO THE FORECAST...AS THE FRONT
PASSES THROUGH THE AREA IN THE OVERNIGHT HOURS. CONDITIONS WILL
DRY OUT FROM WEST TO EAST LATE TUESDAY AFTERNOON INTO THE EVENING
HOURS.

LONG TERM...TUESDAY NIGHT THROUGH SUNDAY...GOOD MODEL AGREEMENT
ON THE RE-DEVELOPING SW FLOW FOR WEDNESDAY AND THURSDAY STARTS TO
DETERIORATE FRIDAY AND BY SUNDAY THE MORE PROGRESSIVE GFS IS OUT
OF PHASE WITH THE SLOWER ECMWF. THE GEFS IS SLOWER THAN THE GFS SO
A GEFS/ECMWF SOLUTION IS PREFERRED BUT CONFIDENCE IN TIMING BY
LATE WEEKEND IS LOW. MOISTENING SW FLOW IS EXPECTED THURSDAY
THROUGH SATURDAY. COULD SEE A COLD FRONTAL PASSAGE SATURDAY NIGHT.
THE FRONT WOULD BE FOLLOWED BY ITS ASSOCIATED A COOL UPPER
TROUGH...PROBABLY SUNDAY. THEN LOOK FOR ANOTHER TRANSIENT RIDGE
MONDAY. INCREASED POPS AND SKY COVER FRIDAY WITH THE BIT FASTER
EC/GEFS TIMING. FOR SUNDAY/MONDAY...WENT WITH A BIT BELOW CLIMO
POPS AND ABOVE CLIMO TEMPS. MAIN CHANGE THIS PACKAGE WAS TO RAISE
POPS/QPF LATE WEDNESDAY THROUGH FRIDAY.

&&

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

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...SP
AVIATION.....SP
PREV SHORT TERM...KA
PREV LONG TERM....VM



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