Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 050932
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
332 AM MDT THU MAY 5 2016

.SHORT TERM...TODAY THROUGH FRIDAY...A LARGE UPPER LEVEL LOW
CONTINUES TO MOVE SLOWLY EAST JUST OFF THE COAST OF CENTRAL CA.
OUR AREA IS IN SRLY FLOW ALOFT THIS MORNING. THIS FLOW WILL BACK
TO SSERLY BY THIS AFTERNOON AND BECOME INCREASINGLY DIFFLUENT. THE
LOW MOVES INLAND TONIGHT AND BECOMES CENTERED OVER SRN CA BY
FRIDAY AFTERNOON. AS THIS OCCURS...OUR UPPER FLOW CONTINUES TO
BACK THROUGH SERLY TO ERLY. COOL AIR ALOFT...COMBINED WITH WARM
AND RELATIVELY MOIST AIR A LOW TO MID-LEVELS...WILL RESULT IN
FURTHER INCREASES IN INSTABILITY. SPC HAS PLACED MAINLY THE NW
PORTION OF THE AREA IN A MARGINAL RISK FOR SEVERE WEATHER
TODAY...AND THE ENTIRE AREA IN THE MARGINAL RISK FOR FRIDAY. AS A
CLARIFICATION...MARGINAL IS A CATEGORY CREATED TO EXPRESS A RISK
OF SEVERE WEATHER THAT DOES NOT QUITE RISE TO WHAT THEY PUT IN A
SLIGHT RISK OUTLOOK...BUT IS SLIGHTLY HIGHER THAN WHAT THEY CALL
GENERAL THUNDERSTORMS. THEREFORE WE SHOULD BE ON THE LOOKOUT FOR
ISOLATED SEVERE THUNDERSTORMS BOTH TODAY AND TOMORROW...BUT
CONFIDENCE IS NOT AS HIGH AS IF THEY HAD PUT US IN A SLIGHT RISK
CATEGORY. WITH THE LARGE LOW TO THE SOUTH...THE WIND PROFILE IS
NOT WHAT WE TYPICALLY GET WITH A RISK OF SEVERE WEATHER. STORMS
WILL BE MOVING NEARLY DUE NORTH TODAY...AND OUT OF THE EAST ON
FRIDAY. MOISTURE WILL INCREASE EACH DAY...AND MODERATE TO HEAVY
RAIN IS POSSIBLE...ESPECIALLY ON FRIDAY. TEMPS THROUGH THE SHORT
TERM WILL BE ABOVE NORMAL...ESPECIALLY AT NIGHT WHEN WINDS AND
CLOUDS WILL INHIBIT COOLING. CLOUDS DURING THE DAY...ALONG WITH
THE EXACT TIMING AND LOCATION OF THE EARLIEST SHOWERS...WILL
DETERMINE HOW WARM ANY GIVEN LOCATION GETS. AS WE EXPECT THE BULK
OF CONVECTION TO BE ON THE OREGON SIDE TODAY...WE HAVE THE WARMEST
TEMPS ON THE IDAHO SIDE IN THE SNAKE RIVER PLAIN. FRIDAY...WITH
MORE CLOUDS AND EARLIER CONVECTION FORECAST...TEMPS COOL 5 TO 8
DEGREES COMPARED TO TODAY ON THE IDAHO SIDE AND IN FAR SOUTHEAST
OREGON...WHILE CHANGING VERY LITTLE FROM BURNS NORTHEAST INTO
BAKER COUNTY. THE SURFACE LOW WILL STRENGTHEN ACROSS FAR SW IDAHO
THIS AFTERNOON...AND THEN A LITTLE FARTHER SOUTH INTO NE NV
FRIDAY. THIS WILL ALLOW A STRONG GRADIENT TO DEVELOP ACROSS SE
OREGON AND THEREFORE WINDS...ESPECIALLY WHEN COMBINED WITH
SHOWERS AND STORMS...WILL BE QUITE GUSTY AT TIMES. HOWEVER IT IS
NOT FORECAST TO BE STRONG ENOUGH FOR AN ADVISORY. ISOLATED GUSTS
WITH CONVECTION WILL RANGE FROM 30 TO 50 MPH...AND SMALL HAIL IS
POSSIBLE AS WELL...BOTH TODAY AND TOMORROW. THE GREATER COVERAGE
OF STORMS OVERALL IS EXPECTED TOMORROW...BUT THIS AFTERNOON AND
EVENING IN SE OREGON...ESPECIALLY HARNEY AND WRN BAKER
COUNTIES...WILL SEE NUMEROUS STORMS. THESE WILL LIKELY COME IN
SEVERAL EPISODES STRETCHING FROM THE AFTERNOON WELL INTO THE
EVENING AND POSSIBLY LASTING WELL AFTER MIDNIGHT.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...SHOWERS AND
THUNDERSTORMS WILL CONTINUE WELL INTO FRIDAY EVENING OVER
SOUTHWESTERN IDAHO AND SOUTHEASTERN OREGON. SHOWERS AND
THUNDERSTORMS WILL MOVE FROM EAST TO WEST AS DEEP EASTERLY FLOW AT
THE SURFACE AND ALOFT CONTINUES OVER THE AREA. THE UNUSUAL EAST TO
WEST STORM MOTION IS DUE TO THE LOCATION OF A VERY LARGE CYCLONIC
CIRCULATION CENTERED SOUTH OF THE FORECAST AREA. THE CIRCULATION
ASSOCIATED WITH THIS SYSTEM WILL ENCOMPASS THE ENTIRE WESTERN
UNITED STATES ON SATURDAY AND BRING A CONTINUATION OF SHOWERS AND
THUNDERSTORMS TO OUR AREA. SOME AREAS OF SOUTHERN OREGON AND
SOUTHERN IDAHO COULD SEE OVER AN INCH OF RAIN...ESPECIALLY IN THE
MOUNTAINS. ON SUNDAY A NEW SHORT WAVE TROUGH WILL APPROACH THE
AREA FROM THE NORTHWEST AND HELP PUSH THE LARGE UPPER LOW INTO THE
CENTRAL U.S. TEMPERATURES WILL REMAIN ABOUT 5 DEGREES ABOVE NORMAL
THROUGH THE WEEKEND...THOUGH SOME AREAS WILL BE A BIT RAIN COOLED
ON SATURDAY WHICH MAY HOLD TEMPERATURES DOWN A BIT BELOW THE
CURRENT FORECAST. COOLER AND DRIER AIR BEHIND THE SHORTWAVE TROUGH
MOVING IN FROM THE NORTHWEST WILL BRING TEMPERATURES DOWN TO NEAR
NORMAL MONDAY THROUGH WEDNESDAY. THERE COULD STILL BE SOME RAIN
AND SNOW SHOWERS IN THE CENTRAL IDAHO MOUNTAINS MONDAY THROUGH
WEDNESDAY... BUT EXPECT DRY WEATHER ACROSS MOST OF SOUTHWESTERN
IDAHO AND SOUTHEASTERN OREGON.

&&

.AVIATION...SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
DEVELOP IN EASTERN OREGON THIS AFTERNOON. EXPECT RAIN...SMALL HAIL
AND VERY GUSTY SFC WINDS IN THE VICINITY OF THESE THUNDERSTORMS.
ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE IN IDAHO.
OTHERWISE...EXPECT VFR CONDITIONS OUTSIDE OF THUNDERSTORM
ACTIVITY. SURFACE WINDS...10 TO 15 KTS. WINDS ALOFT UP TO 10K FT
MSL...SOUTHEASTERLY AT 25 KTS.

&&

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

&&

$$

WWW.WEATHER.GOV/BOISE
WWW.FACEBOOK.COM/NWSBOISE
WWW.TWITTER.COM/NWSBOISE

SHORT TERM...SP
LONG TERM....JB
AVIATION.....JB



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