Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 050908
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
308 AM MDT THU MAY 5 2016

.SHORT TERM...TODAY THROUGH SATURDAY...FANTASTIC MODEL AGREEMENT
REGARDING PLACEMENT OF CLOSED UPPER LOW OFFSHORE CALIFORNIA TODAY.
THIS LOW IS FORECAST TO TRACK ACROSS THE SOUTHWEST U.S. FRIDAY AND
WILL PROVIDE US WITH INCREASED RAIN POTENTIALS BY THE END OF THIS
WEEK. INSTABILITY FRIDAY AFTERNOON AND EVENING ACROSS OUR STATE
SHOWS WIDESPREAD 800+ J/KG CAPE VALUES...ESPECIALLY IN THE
SOUTHERN AREAS. NAM MODEL IS SHOWING FAIRLY SIGNIFICANT SEVERE
PARAMETERS THROUGHOUT THE SNAKE RIVER VALLEY INCLUDING A DECENT
HAIL THREAT AND A POSSIBLE HEAVY RAIN EVENT. ABOUT THE SAME STORY
EXISTS SATURDAY AFTERNOON AND EVENING...BUT PERHAPS A WEAKENED
THREAT THOUGH CERTAINLY THUNDERSTORM ARE STILL POSSIBLE AND WE
SHOULD NOT LET ANY GUARDS DOWN.

QUITE A BIT OF RAINFALL LOOKS TO BE ON TAP THESE TWO DAYS.
FOLLOWING NAM GUIDANCE...AREAS EXPECTING THE MOST RAIN WILL BE
BEAR LAKE TO POCATELLO TO THE INL AND INTO MACKAY. THERE WILL
LIKELY BE BREAKS IN THE HEAVIEST RAINFALL WITH THE FIRST WAVE
FRIDAY EVENING AND THE SECOND ONE SATURDAY AFTERNOON. STORM TOTAL
PRECIP AMOUNTS OVER A 48 HOUR PERIOD COULD EXCEED AN INCH OR MORE
IN THESE AREAS. WILL ALSO BE WATCHING NORTHEASTERLY WINDS FRIDAY
AFTERNOON EXPECTED TO INCREASE FOR THE NORTHERN HALF OF OUR CWA
AND COULD REACH SPEEDS IN EXCESS OF 20 TO 25 MPH...HIGHER AT
MOUNTAIN PASSES. THIS TREND WOULD PERSIST OVERNIGHT BEFORE
IMPROVING EARLY SATURDAY MORNING.

ONE MORE WARM DAY WITH TEMPERATURES IN THE UPPER 70S TO LOW 80S
FOR THE VALLEY FLOORS AND 60S IN THE MOUNTAINS. ABOUT 10 DEGREES
COOLER TOMORROW FOLLOWED BY THE COOLEST AIR SATURDAY BUT EVEN THAT
IS ONLY IN THE 50S AND 60S FOR HIGHS BEFORE RECOVERY BEGINS AGAIN
BY THE LATTER HALF OF THE WEEKEND. NP/HUSTON

.LONG TERM...SUNDAY THROUGH NEXT THURSDAY. THE GFS AND ECMWF WERE IN
FAIR AGREEMENT THIS MORNING ALTHOUGH RUN TO RUN DIFFERENCES WERE
OBSERVED. THE MODELS SHOW THE UPPER LOW GRADUALLY LIFTING NE
INTO/ACROSS COLORADO/WYOMING SUNDAY WHILE A PAC TROUGH DIGS SSE
THROUGH WRN CANADA. THE INTERPLAY BETWEEN THESE SYSTEMS WAS
SUPPORTING WIDESPREAD SHOWER ACTIVITY ACROSS SE IDAHO SUNDAY
AFTERNOON. BY MONDAY...THE TROUGH DROPPING SE OUT OF CANADA SPINS UP
A CLOSED LOW CIRCULATION OVER THE NRN ROCKIES (STRONGER AND A BIT
FURTHER SW THAN PREVIOUS RUNS) RESULTING IN WINDY CONDITIONS
THROUGHOUT THE ERN MAGIC VALLEY/SNAKE PLAIN AND NUMEROUS SHOWERS
WITHIN THE CNTRL AND NE MOUNTAINS. THE LOW GRADUALLY SHIFTS EAST
ACROSS WYOMING TUESDAY WITH WEAK INSTABILITY SHOWERS LINGERING
ACROSS SE IDAHO UNDER THE WRN EXTENT OF THE EXITING LOW. THE
INFLUENCE OF THE LOW DECREASES WEDNESDAY AND THURSDAY BUT THE
PICTURE BECOMES A BIT UNCERTAIN WITH THE TRACK OF SECONDARY
DISTURBANCES TRAILING ACROSS THE NRN ROCKIES. BOTH THE GFS AND ECMWF
STATISTICAL GUIDANCE WERE SHOWING A FAIRLY DECENT COOLING TREND
ASSOCIATED WITH THE SECOND TROUGH DIGGING MORE SHARPLY SOUTH OUT OF
CANADA MONDAY AND TUESDAY AND THUS HAVE COOLED THE GOING FORECAST
SOME TO REFLECT THIS CHANGE. HUSTON

&&

.AVIATION...UPPER LOW POSITIONED OFF THE SOUTH-CNTRL CALIFORNIA
COAST EARLY THIS MORNING WITH ASSOCIATED SHOWERS/CONVECTION
STREAMING NORTH ACROSS THE NRN SIERRA/CASCADES. FURTHER EAST ACROSS
THE GREAT BASIN...INCREASING MID AND UPPER CLOUDS WERE ADVANCING
NORTH THROUGH NEVADA TOWARD SRN IDAHO. NUMERICAL MODELS SHOW THE LOW
SPREADING INTO SRN CALIFORNIA OVERNIGHT WITH INCREASING MOISTURE AND
SHOWER ACTIVITY EXPECTED ACROSS SE IDAHO BEGINNING LATE THIS
AFTERNOON AND INCREASING THROUGH THE NIGHT. MODEL CROSS SECTIONS
MAINTAIN VFR BKN-OVC CIGS THROUGHOUT THE FORECAST PERIOD. HUSTON


&&

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

$$



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