Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 060237
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
837 PM MDT THU MAY 5 2016

.DISCUSSION...SHOWERS AND THUNDERSTORMS HAVE BEEN ONGOING THROUGH
THIS AFTERNOON AND EVENING AS FORECASTED. A FEW OF THESE STORMS
THAT WERE STRONGER PRODUCED SMALL HAIL AND HEAVY RAIN. UPDATED THE
FORECAST SLIGHTLY TO LOWER POPS IN AREAS WHERE CONVECTION IS LESS
LIKELY...BUT SHOWERS MAY CONTINUE OVERNIGHT. FLASH FLOOD WATCH
WILL CONTINUE IN BAKER COUNTY OREGON FOR THE CORNET WINDY RIDGE
BURN SCAR AS CONVECTION IS STILL ONGOING AND NEARBY THE SCAR.

&&

.AVIATION...GENERALLY VFR. AT 02Z SCATTERED THUNDERSTORMS WITH HEAVY
RAIN AND HAIL EXTENDED FROM KBNO THROUGH KBKE TO KMYL...MOVING
NORTH.  AREAS OF MOUNTAIN OBSCURATION WITH LOCAL IFR IN HEAVY PCPN.
ISOLATED -TSRA FARTHER SOUTH...ALSO MOVING NORTH. THUNDERSTORMS
SHOULD END BY 07Z BUT SCATTERED -SHRA WILL CONTINUE PAST 12Z.
SURFACE WINDS NORTHWESTERLY 10-20 KTS IN OREGON AND WESTERN IDAHO
...NORTHEASTERLY IN SOUTH-CENTRAL IDAHO...AND VARIABLE ELSEWHERE IN
IDAHO. THUNDERSTORM GUSTS TO 35 KTS.  WINDS ALOFT SOUTHEAST 20-30
KTS.

&&

.PREV DISCUSSION...
SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT...AN UPPER LEVEL LOW
CENTERED JUST OFF THE CENTRAL CALIFORNIA COAST WILL BE THE MAIN
WEATHER FEATURE THROUGH THE SHORT TERM. SHOWERS AND THUNDERSTORMS
WILL INCREASE IN COVERAGE ACROSS THE FORECAST AREA LATE THIS
AFTERNOON AND EARLY EVENING AIDED BY DIFFLUENT FLOW ALOFT
NORTHEAST OF THE LOW CENTER. ENOUGH MOISTURE AND INSTABILITY IN
DEEP SOUTHERLY FLOW FOR ORGANIZED STORMS WITH GUSTY WINDS AND
SMALL HAIL THROUGH THIS EVENING...ESPECIALLY ON THE OREGON SIDE
AND ACROSS THE WEST CENTRAL MOUNTAINS IN IDAHO. HEAVY RAIN THREAT
APPEARS GREATEST OVER EASTERN OREGON ZONES BUT NOT SO MUCH FROM
SLOW MOVING STORMS AS FROM STORM CELLS MOVING OVER THE SAME AREA.

A DOWNWARD TREND IN PRECIPITATION COVERAGE WILL OCCUR OVERNIGHT
WHILE THE LOW MOVES INLAND. ACTIVITY WILL RAMP UP IN DAYTIME
INSTABILITY ON FRIDAY. FLOW ALOFT WILL BACK TO EASTERLY AS THE LOW
CENTER MOVES FURTHER INLAND ACROSS THE SOUTHERN GREAT BASIN.
PARAMETERS LOOK EVEN BETTER FOR STRONG STORMS ON FRIDAY AFTERNOON
AND EVENING WITH LOCALLY HEAVY RAIN...STRONG GUSTY WINDS AND
SMALL HAIL WITH SOME STORMS. GREATEST COVERAGE OF SHOWERS AND
THUNDERSTORMS AND HIGHEST PRECIPITATION AMOUNTS ARE EXPECTED
ACROSS THE SOUTHERN HALF OF THE FORECAST AREA. DAYTIME HIGHS WILL
TREND DOWN SOME ON FRIDAY WITH INCREASED CLOUDS AND PRECIPITATION
COVERAGE WITH OVERNIGHT LOWS STAYING ABOVE NORMAL DUE TO CLOUDS
AND MOISTURE.

.LONG TERM...SATURDAY THROUGH THURSDAY...LARGE UPPER LOW WILL
CONTINUE ITS JOURNEY EAST...WITH WRAP AROUND MOISTURE ALLOWING FOR A
CONTINUATION OF SHOWERS AND AFTERNOON/EVENING THUNDERSTORMS OVER THE
REGION SATURDAY. PWAT VALUES ARE EXPECTED TO BE OVER THE 90TH
PERCENTILE...SO THE MAIN CONCERN WILL BE THE AMOUNT OF PRECIPITATION
PRODUCED BY ANY INDIVIDUAL THUNDERSTORM. HIGHEST AMOUNTS WILL BE
OBSERVED IN THE HIGHER ELEVATIONS. SOME LOCATIONS COULD SEE BETWEEN
A HALF AN INCH TO AN INCH OF PRECIP. SUNDAY WILL SEE A DECREASE IN
PRECIP AND CLOUD COVERAGE AS A TROUGH DIPS SOUTH OUT OF CANADA AND
KICKS THE DOMINATING UPPER LOW OUT OF THE REGION. SHOWERS AND
AFTERNOON/EVENING THUNDERSTORMS LOOK TO BE ISOLATED TO SOUTHWEST
IDAHO...MAINLY OVER THE MOUNTAINS. HOWEVER...MODELS STILL SEEM TO BE
TRYING TO RESOLVE THE INTERACTION BETWEEN THESE LOWS...SO COULD
STILL SEE A FEW MODIFICATIONS IN COVERAGE IN THE NEXT FEW DAYS. AS
THE THROUGH MOVES SOUTH OUT OF CANADA...IT IS EXPECTED TO DEEPEN AND
BRING MORE CHANCES OF SHOWERS AND THUNDERSTORMS TO THE MOUNTAINS
NORTH OF THE SNAKE RIVER PLAIN. THIS TROUGH WILL CAUSE THE COOLEST
TEMPERATURES OF THE PERIOD WITH ABOUT A TEN DEGREE DROP BETWEEN
SUNDAY AND MONDAY...TEMPERATURES WILL HAVE BEEN ABOUT 5-10 DEGREES
ABOVE NORMAL UP UNTIL THIS POINT. SNOW LEVELS WILL DROP TO ABOUT
5.5K TO 6.5 K FT MSL...MONDAY INTO TUESDAY. AS THE TROUGH MOVES EAST
OF THE REGION TUESDAY...WILL SEE DRYING CONDITIONS AND INCREASING
TEMPERATURES. TEMPERATURES ARE EXPECTED TO BOUNCE BACK TO ABOUT 5-10
DEGREES ABOVE NORMAL BY THE END OF THE PERIOD.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...FLASH FLOOD WATCH UNTIL MIDNIGHT PDT TONIGHT ORZ062.

&&

$$

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WWW.FACEBOOK.COM/NWSBOISE
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DISCUSSION...EP
AVIATION.....LC
PREV SHORT TERM...TL
PREV LONG TERM....AB/WH


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