Flash Flood in Idaho, May 8, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
152 PM MDT FRI MAY 8 2015

.SHORT TERM...TONIGHT THROUGH MONDAY. UPPER LOW MIGRATES ACROSS
THE FOUR COURNERS REGION TONIGHT AND SATURDAY. WV IMAGERY SHOWS
EAST IDAHO ON THE EDGE OF MOIST DIFLUENT FLOW. SHOWERS ALREADY
DEVELOPING WITH A COUPLE ISOLATED THUNDERSTORMS IN UNSTABLE
AIRMASS. LITTLE SHEAR TO WORK WITH SO EXPECT SMALL HAIL AND
LOCALLY HEAVY RAINFALL. UPPER TROUGH AXIS SLIPS PAST THE REGION
INTO SATURDAY WITH REGION UNDER INCREASING NORTHERLY FLOW
INFLUENCE. WRAP AROUND MOISTURE LIKELY TO CATCH SOUTHEAST
QUADRANTS OF FCST AREA WITH CONTINUED SHOWERS. BOTH NAM/GFS AGREE
ON PUSHING BAND OF MODERATE QPF MOISTURE INTO SOUTHEAST CORNER
SATURDAY AFTERNOON. SOME QUESTION AS TO HOW FAR WEST THE BAND WILL
PUSH SO KEPT HIGHEST POPS OVER BEAR LAKE REGION AND FADED TO
SLIGHT CHANCE INTO THE SNAKE PLAIN. NORTHERLY SFC GRADIENT
INCREASES THROUGH THE DAY AND LAKE WIND ADVISORY WILL BE NEEDED
FOR THE DAYLIGHT HOURS FOR AMERICAN FALLS RES BOATING INTERESTS.
TREND SHIFTS DRIER HEADING INTO SUNDAY AS UPPER LOW MIGRATES INTO
THE PLAINS AND TRANSITORY RIDGE BUILDS INTO THE INTERMOUNTAIN
WEST. SOUTHWEST FLOW ALOFT RETURNS ON MONDAY WITH NEXT POTENTIAL
SET OF CONVECTION. HAVE PUSHED POPS HIGHER DURING THE DAY MONDAY
ESPECIALLY AFTERNOON AND EVENING AS SHORTWAVE ROTATES THROUGH
OREGON INTO WESTERN IDAHO AHEAD OF NEXT UPPER LOW. DMH

.LONG TERM...MONDAY NIGHT THROUGH NEXT FRIDAY. LOOKING AT A
BROAD...MOIST SOUTHWESTERLY FLOW ALOFT EARLY NEXT WEEK WITH BOTH GFS
AND ECMWF DEPICTING AN UPPER LOW JUST OFF THE WA/OR COAST. THE ECMWF
IS COMING IN JUST A BIT FURTHER SOUTH WITH THE UPPER LOW...BUT BOTH
MODELS ARE CONSISTENT IN SPREADING PRECIP ACROSS SOUTHEAST IDAHO
MONDAY NIGHT AND TUESDAY. GFS LIFTS UPPER LOW ACROSS WA/OR TUESDAY
NIGHT/WEDNESDAY AS ANOTHER LOW ENTERS THE TROUGH OFF THE COAST
WEDNESDAY NIGHT. ECMWF TRIES TO LIFTS THE LOW FURTHER INLAND...BUT
TRIES TO MODEL INTERACTION BETWEEN THAT LOW...THE LOW IN THE PACIFIC
AND A THIRD UPPER LOW IN ALBERTA. MINOR ADJUSTMENTS TOWARDS WETTER
CONDITIONS MON THRU WED. FAVORING GFS SOLUTION FOR THURS AND FRI
WITH MOST OF THE PRECIP ASSOCIATED WITH THE UPPER LOW STAYING TO THE
WEST...HOWEVER KEPT SLIGHT POPS IN FOR FRI GIVING A SLIGHT NOD TO
THE ECMWF. HINSBERGER

&&

.AVIATION...AIRMASS IS CONVECTIVELY UNSTABLE AGAIN THIS AFTERNOON
AND LOCAL WRF/HRRR WIDELY VARYING IN TIMING OF CONVECTION THROUGHOUT
THE DAY. SHOOTING FOR MID-AFTERNOON FOR START OF VCTS AT THE
TERMINALS WITH SHOWERS LIKELY. SHOULD SEE VFR CONDITIONS THROUGH THE
PERIOD...BUT MAY SEE VIS BRIEFLY DROP IN HEAVIER SHOWERS. THUNDER
WILL SUBSIDE THIS EVENING AS WE STABILIZE AGAIN. CLEARING SHOULD
COME AROUND EARLY TO MID MORNING AS NORTHERN BRANCH OF UPPER TROUGH
PASSES EAST...BUT NORTH/NORTHEASTERLY WINDS EXPECTED TO PICK UP AS
WELL. HINSBERGER

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
NONE.
&&