706  
FXUS65 KPIH 230828  
AFDPIH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE POCATELLO ID  
228 AM MDT THU MAR 23 2017  
   
SHORT TERM...TODAY THROUGH SATURDAY
 
A FAIRLY QUIET DAY IS  
EXPECTED WITH A WEAK HIGH PRESSURE RIDGE IN PLACE. A CHANCE FOR  
RAIN AND SNOW SHOWERS WILL EXIST IN THE EASTERN HIGHLANDS THIS  
MORNING BEFORE THE RIDGE BUILDS OVER THIS AREA LATER THIS EVENING.  
THE RIDGE WILL BE IN PLACE THROUGH FRIDAY EVENING WHEN AN  
APPROACHING UPPER TROUGH ARRIVES LATE FRIDAY INTO SATURDAY  
MORNING. THIS TROUGH WILL INCREASE RAIN AND SNOW POTENTIALS  
SUBSTANTIALLY. ELEVATIONS ABOVE 6500 FT ARE EXPECTED TO RECEIVE 4  
TO 8 INCHES OF NEW SNOW ACROSS THE SAWTOOTH MOUNTAINS AND SALMON-  
CHALLIS NATIONAL FORESTS. ELEVATIONS BETWEEN 6000 AND 6500 FT ARE  
EXPECTED TO SEE CLOSER TO 1 TO 2 INCHES OF SNOWFALL WITH RAIN  
FALLING BELOW 6000 FT FOR THE REST OF THE CENTRAL MOUNTAIN REGION.  
UPPER SNAKE, CARIBOU AND EASTERN HIGHLAND LOCATIONS MAY ALSO SEE  
SOME SNOWFALL WITH 2 TO 4 INCH AVERAGE AMOUNTS FORECAST DURING  
THIS PERIOD. FOR LOCATIONS EXPECTED TO EXPERIENCE RAINFALL, BELOW  
6000 FT, RAINFALL AMOUNTS OF 1/10 TO 1/4 INCH TOTALS ARE POSSIBLE  
OVER A 30 HOUR PERIOD FRIDAY EVENING THROUGH SATURDAY.  
 
THE PRECIPITATION POTENTIALS FOR LATE SATURDAY INTO SUNDAY MORNING  
HAVE BEEN CUT IN HALF ACROSS THE CENTRAL MOUNTAINS AS THROUGH  
RESPONSIBLE FOR THE EXPECTED ACTIVITY LOOKS TO BRING HEAVIEST  
ACTIVITY TO THE NORTH OF THIS REGION. A SPLIT FLOW PATTERN LOOKS  
TO SET UP DURING THIS PERIOD WITH HEAVIER ACTIVITY IN THE IDAHO  
PANHANDLE AND ACTIVITY OVER UTAH AND SOUTHERN IDAHO. THE SNAKE  
PLAIN AND MOST OF SOUTHEAST IDAHO IS LOOKING MORE DRY FOR SATURDAY  
INTO SUNDAY AT THIS TIME. THIS IS NOT TO SAY ALL AREAS WILL BE  
PRECIP-FREE AND AREAS LIKE BEAR LAKE AND THE SOUTHERN HIGHLANDS  
ARE CURRENTLY FORECAST TO EXPERIENCE SOME SHOWERY ACTIVITY.  
NP/KEYES  
 

 
   
LONG TERM
 
SUNDAY THROUGH NEXT THURSDAY. MODELS CONTINUE TO  
ADVERTISE SPLIT FLOW ACROSS THE WESTERN U.S. NEXT WEEK. RIGHT NOW,  
MONDAY AND THURSDAY LOOK TO BE THE WETTEST DAYS. HOWEVER, THE  
DEGREE OF SPLIT FLOW HAS BEEN SWINGING BACK AND FORTH A BIT WHICH  
WOULD AFFECT TIMING AND/OR PRECIPITATION AMOUNTS. IF WE END UP IN  
BETWEEN THE NORTHERN AND SOUTHERN BRANCHES, WE CAN END UP FAIRLY  
DRY. IF THE SOUTHERN STREAM DOESN'T HEAD SOUTH FAR ENOUGH AND/OR  
THE NORTHERN STREAM HITS EASTERN IDAHO, THEN WE COULD END UP WITH  
QUITE A BIT OF LOWER ELEVATION RAIN AND MOUNTAIN SNOWFALL. LESS  
SPLITTING MEANS THE CURRENT TIMING PATTERN WOULD BE A BIT SLOW.  
BEING OUT WEST, SOMETIMES THE MODELS STRUGGLE WITH THIS PATTERN  
UNTIL THESE STORMS ARE ALMOST ASHORE. EITHER WAY, THE CURRENT  
PATTERN SHOULD SHAVE A FEW DEGREES OFF TEMPERATURES, BUT NOTHING  
THAT WOULD HELP SLOW DOWN ANY SNOWMELT AND FLOODING PROBLEMS  
EXCEPT AT NIGHT IN SOME PLACES. KEYES  
 

 
   
AVIATION
 
SHOWERS CONTINUE ACROSS THE SOUTHEAST CORNER OF IDAHO  
EXTENDING NORTHWARD ALONG THE WYOMING BORDER TOWARD DRIGGS. THAT  
PATTERN IS EXPECTED THROUGH THE REST OF THE DAY, ALTHOUGH THE TREND  
WILL SLOWLY DOWNWARD. RIGHT NOW, KDIJ IS MVFR (FLIRTING WITH IFR  
ACTUALLY). THEY ARE THE MOST LIKELY CANDIDATE FOR OCCASIONAL  
SHOWERS AND/OR CEILINGS OTHER THAN VFR THROUGH THE DAY AND INTO  
TONIGHT. CROSS SECTIONS INDICATE THAT WE COULD SEE A BRIEF PERIOD OF  
MVFR/IFR AT KIDA, KPIH OR KBYI EARLY ON. WITH RAIN IN THE PAST 24  
HOURS, IT'S CERTAINLY POSSIBLE SO WE AREN'T GOING TO SAY NO BUT NOT  
NECESSARILY GO FULL BLAST IN THAT DIRECTION. IT SHOULD REMAIN DRY AT  
THOSE SITES IT APPEARS HOWEVER. STRONGER WEST WINDS ARE EXPECTED AT  
KBYI AND KPIH, 15-25KTS INCLUDING GUSTS. KSUN APPEARS AS THE WINNER  
WHEN IT COMES TO CONFIDENTLY REMAINING VFR THROUGHOUT THE DAY.  
KEYES  
 

 
   
HYDROLOGY
 
ADDITIONAL RAINFALL IS EXPECTED LATE FRIDAY INTO  
SATURDAY MORNING WITH 1/10 TO 1/4 INCH AMOUNTS FORECAST. SOME  
AREAS MAY RECEIVED UP TO 1/2 INCH OVER A 36 HOUR PERIOD,  
INCLUDING AREAS ALONG THE CONTINENTAL DIVIDE INCLUDING ISLAND  
PARK, THE BEAR LAKE REGION AND CACHE VALLEY OF IDAHO. THIS RAIN  
WILL ADD TO FLOODING RISK IN THESE AREAS. BECAUSE OVERNIGHT  
TEMPERATURES ARE COOLER NOW AND WILL CONTINUE TONIGHT AND SATURDAY  
MORNING, AT OR BELOW FREEZING, A POSSIBLE SLOW DOWN TO THE  
SNOWMELT FLOODING MAY OCCUR. AREAL FLOOD WATCHES WILL PERSIST  
UNTIL FURTHER NOTICE FOR ALL AREAS PREVIOUSLY UNTIL THE WATCH.  
 
THE PORTNEUF AND BEAR RIVERS CONTINUE TO RUN HIGH. THE PORTNEUF  
REMAINS UNDER A FLOOD WARNING WITH LATEST FORECASTS STILL SOLIDLY  
PUSHING INTO MODERATE FLOOD CATEGORY SATURDAY NIGHT AND STAYING  
THERE INTO THE BEGINNING OF APRIL. THE BEAR IS CURRENTLY IN ACTION  
STAGE AND EXPECTED TO REACH MINOR FLOODING THIS EVENING THROUGH  
SATURDAY. NP/KEYES  
 

 
   
PIH WATCHES/WARNINGS/ADVISORIES
 
 
FLOOD WATCH UNTIL NOON MDT TODAY FOR IDZ017>019-022>025-031-032.  
 

 
 

 
 
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