Severe Thunderstorm Warning 1, NWS Boise, ID

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

.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.

&&

.AVIATION...VFR. INCREASING BKN-OVC MID-HIGH LEVEL CLOUDS.
ISOLATED SHOWERS AND THUNDERSTORMS ESPECIALLY IN SE
OREGON...DECREASING OVERNIGHT. THUNDERSTORMS TODAY COULD POTENTIALLY
PRODUCE GUSTY WINDS AND SMALL HAIL. SCT-NUMEROUS THUNDERSTORMS
DEVELOPING FRIDAY ACROSS THE REGION. FRI THUNDERSTORMS WILL BE
ASSOCIATED WITH HEAVY RAIN...GUSTY WINDS...AND SMALL HAIL. SURFACE
WINDS TODAY...GENERALLY SOUTHEASTERLY 12 KTS OR LESS...EXCEPT GUSTS
TO 35KT IN VICINITY OF SHOWERS AND THUNDERSTORMS. WINDS ALOFT AROUND
10K FT MSL...SOUTH TO EAST 20-30 KTS.

&&

.HYDROLOGY...FLASH FLOOD CONCERNS ACROSS EASTERN OREGON LATE THIS
AFTERNOON AND EVENING...PRIMARILY OVER BAKER COUNTY WHERE THE
CORNET WINDY RIDGE BURN SCAR IS FROM LAST SUMMER. OTHER HYDROLOGY
CONCERN IS IN SOUTHERN OWYHEE COUNTY ON THE EAST FORK OF THE
JARBIDGE RIVER WHERE ABOVE NORMAL HIGH ELEVATION SNOWPACK EXISTS.
DIURNAL PEAK ON THE STREAM GAGE AT MURPHY HOT SPRINGS TRENDED UP
AGAIN LAST NIGHT DUE TO WARM TEMPERATURES EATING AWAY AT THE SNOW.
WILL NEED TO WATCH STREAM GAGE TRENDS AGAIN TONIGHT IN ADDITION TO
RAINFALL IN THIS AREA THE NEXT COUPLE OF DAYS WITH POTENTIAL FOR
BANKFULL CONDITIONS OR MINOR FLOODING IN THE HOT SPRINGS AREA.

&&

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

&&

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

SHORT TERM...TL
LONG TERM....AB/WH
AVIATION.....AB
HYDROLOGY...TL

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BOISE ID
358 PM MDT THU MAY 5 2016

IDZ015-029-ORZ063-052230-
OWYHEE MOUNTAINS ID-SOUTHWEST HIGHLANDS ID-MALHEUR COUNTY OR-
358 PM MDT THU MAY 5 2016

...SIGNIFICANT WEATHER ADVISORY FOR EAST CENTRAL MALHEUR COUNTY UNTIL
430 PM MDT...

AT 357 PM MDT...DOPPLER RADAR WAS TRACKING A STRONG THUNDERSTORM OVER
CLIFFS...OR 33 MILES EAST OF ROME...MOVING NORTHWEST AT 55 MPH.

NICKEL SIZE HAIL AND WINDS IN EXCESS OF 40 MPH WILL BE POSSIBLE WITH
THIS STORM.

THIS STRONG THUNDERSTORM WILL BE NEAR...
  SOUTH MOUNTAIN AROUND 400 PM MDT.
  CASTRO RIDGE AND PARSNIP PEAK AROUND 410 PM MDT.
  ANTELOPE RESERVOIR...LITTLE GRASSY RESERVOIR...LITTLE GRASSY
  MOUNTAIN AND JORDAN VALLEY AROUND 420 PM MDT.
  DANNER AND AROCK AROUND 430 PM MDT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

WHEN SAFE TO DO SO...PLEASE RELAY STORM REPORTS TO THE NATIONAL
WEATHER SERVICE IN BOISE IDAHO VIA LOCAL LAW ENFORCEMENT...OR NWS
BOISE FACEBOOK AND TWITTER ACCOUNTS.

&&

LAT...LON 4262 11683 4250 11705 4295 11760 4314 11717
TIME...MOT...LOC 2157Z 146DEG 48KT 4264 11700

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