Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 231557
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
957 AM MDT SAT MAY 23 2015

.DISCUSSION...MOSTLY CLEAR SKIES OVER THE WEST-CENTRAL AND BOISE
MTNS AND TREASURE VALLEY WILL ADVECT INTO SW HIGHLANDS...OWYHEES
AND FAR WESTERN MAGIC VALLEY THIS AFTERNOON. THIS WILL ALLOW GOOD
HEATING...WHICH IT TURN WILL MAXIMIZE INSTABILITY AND MAKE THESE
AREAS THE MOST LIKELY FOR THUNDERSTORM DEVELOPMENT. UPDATE FOR
CHANGES TO QPF... SKY...AND WEATHER GRIDS OUT SOON.

&&

.AVIATION...MOSTLY VFR WITH SCATTERED TO BROKEN MID LEVEL CLOUD
DECK. WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS EXPECTED
AFTER 18Z. EXPECT HEAVY RAIN AND SMALL HAIL WITH THE STRONGEST
STORMS. SURFACE WINDS LIGHT BEFORE 18Z BECOMING GENERALLY
NORTHWESTERLY 10-20KT THIS AFTERNOON...GUSTS TO 30KT NEAR
THUNDERSTORMS. WINDS ALOFT AT 10K FT MSL...NE 15-25KT.

&&

.PREV DISCUSSION...
SHORT TERM...YESTERDAY THE MAIN MOISTURE AND CONVECTIVE WX WERE
IN NRN ZONES IN IDAHO AND THE WALLOWA MOUNTAINS IN OREGON. THERE
WAS LOCAL FLOODING FRIDAY EVENING NEAR MCCALL AND DONNELLY. TODAY
THE ACTION WILL BE ALMOST ENTIRELY ON THE IDAHO SIDE. GFS
STABILITY CHARTS HAVE VERIFIED BETTER THAN NAM RECENTLY...AND GFS
SHOWS GREATEST INSTABILITY TODAY IN THE BOISE MOUNTAINS AND WEST
CENTRAL IDAHO MOUNTAINS. BUT GREATEST QPF WILL BE ALONG THE
IDAHO/NV BORDER THIS AFTERNOON/EVENING AS UPPER LOW PASSES BY IN
UTAH. YESTERDAY/S MODELS SHOWED THAT TOO. THEREFORE WE EXPECT
QUITE A BIT OF RAIN WITH ONLY ISOLATED THUNDERSTORMS TODAY IN TWIN
FALLS COUNTY AND ERN OWYHEE COUNTY...WHEREAS IN THE IDAHO
MOUNTAINS NORTH OF THE SNAKE BASIN WE EXPECT MORE THUNDERSTORMS
WITH LOCAL HEAVY RAIN. WE WILL AGAIN LET THE DAY CREW DECIDE IF A
FLASH FLOOD WATCH IS NEEDED FOR THOSE NRN MOUNTAINS TODAY.
MEANWHILE...OREGON ZONES WILL HAVE RELATIVELY LESS WX TODAY. DRIER
AIR WILL COME IN FROM THE NORTHWEST LATE TONIGHT AND SUNDAY BUT
ERN-MOST IDAHO ZONES WILL STILL HAVE A CHANCE OF THUNDERSTORMS
SUNDAY AFTERNOON. LITTLE CHANGE IN MAX TEMPS TODAY...THEN ABOUT 3
DEGS WARMER SUNDAY. MILD AND MOIST TONIGHT WITH PATCHY FOG AGAIN
IN THE NRN VALLEYS. MODERATE WEST TO EAST SURFACE PRESSURE
GRADIENT WILL DEVELOP WEST WINDS 15 TO 25 MPH IN THE SNAKE BASIN
AND ALSO NEAR BAKER COUNTY/OR TODAY. LESS WINDY SUNDAY.

LONG TERM...SUNDAY NIGHT THROUGH SATURDAY. MEAN LONG WAVE TROUGH
WILL CONTINUE TO IMPACT THE REGION THROUGH FRIDAY. RESIDUAL MOISTURE
OVER THE REGION WILL KEEP INSTABILITY HIGH ENOUGH FOR AFTERNOON
SHOWERS/THUNDERSTORMS EACH DAY. TEMPERATURES WILL REMAIN NEAR NORMAL
THROUGH FRIDAY. AN UPPER LEVEL RIDGE BEGINS TO BUILD INTO THE REGION
FOR FRIDAY AND SATURDAY. TEMPERATURES WILL RISE TO THE 80S IN THE
LOWER VALLEYS AS WARMER AIR MOVES IN FROM THE SOUTH. THE RIDGE IS
SHORT-LIVED AS MODELS HAVE AN UPPER LEVEL TROUGH FROM THE GULF OF
ALASKA TRANSITIONING INTO THE REGION BY MONDAY.

&&

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

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...SP
AVIATION.....JS
PREV SHORT TERM...LC
PREV LONG TERM....KA



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