397  
FXUS65 KPIH 230500  
AFDPIH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE POCATELLO ID  
1000 PM MST TUE JAN 22 2019  
   
UPDATE
 
A VERY LATE UPDATE TO TWEAK THE OVERNIGHT FORECAST. IN  
THIS CASE MAINLY TO RAISE OVERNIGHT LOWS BASED ON CURRENT TRENDS,  
AND SNOWFALL JUST A BIT. LIGHT SNOW HAS ALREADY STARTED IN A FEW  
PLACES IN THE ISLAND PARK AND TETON VALLEY AREAS. SNOW WILL  
CONTINUE TO SPREAD SOUTH ACROSS EASTERN IDAHO OVERNIGHT. THE BULK  
OF IT SHOULD FALL FROM ISLAND PARK SOUTH THROUGH THE TETON VALLEY,  
BIG HOLES AND INTO THE CARIBOU RANGE. THOSE AREA COULD SEE  
ANYWHERE FROM 1-3" BEFORE SUNRISE. ALONG THE I-15 CORRIDOR SOUTH  
THROUGH MCCAMMON, LOOK FOR VERY LIGHT SNOW ON THE PLAIN FLOOR WITH  
UNDER 1" ALONG THE BENCHES. THE HIGHER PEAKS OF THE BLACKFOOT  
MOUNTAINS, THE MARSH HIGHLANDS AND THE SAWTOOTHS COULD SEE AN  
INCH OR TWO AS WELL. OTHERWISE, LITTLE TO NO SNOW EXPECTED BY  
MORNING. GUSTY WINDS IN SOME PLACES WILL LEAD TO SOME  
BLOWING/DRIFTING. THE HEADLINES FOR TONIGHT AND WEDNESDAY REMAIN  
IN PLACE. THE OVERNIGHT SHIFT WILL NEED TO LOOK AT SNOWFALL  
AMOUNTS TOMORROW AFTERNOON OVER THE EASTERN HIGHLANDS, AS WELL AS  
ALONG 15 AND 86 FROM AROUND POCATELLO WEST TOWARD RAFT RIVER SOUTH  
INTO THE HIGHLANDS. THE MODELS ARE WANTING TO PRODUCE MORE SNOW,  
ESPECIALLY EAST OF I-15 AND AROUND THE BENCHES AROUND POCATELLO.  
KEYES  
 

 
   
PREV DISCUSSION
 
/ISSUED 225 PM MST TUE JAN 22 2019/  
 
SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT.  
 
A POTENT STORM SYSTEM WILL ARRIVE FROM THE NORTHWEST TONIGHT. EXPECT  
SNOW TO SPILL OVER FROM MONTANA INTO THE CENTRAL IDAHO MOUNTAINS,  
EASTERN HIGHLANDS, AND POSSIBLY INTO THE EASTERN SNAKE PLAIN. THIS  
STORM WILL BRING QUITE A BIT OF WIND TO THE AREA, WITH HEAVY SNOW  
LIKELY FOR THE EASTERN HIGHLANDS. STORM TOTAL ACCUMULATIONS OF 5 TO  
8 INCHES WITH HEAVIER AMOUNTS ALONG THE PASSES ARE LIKELY ACROSS THE  
EASTERN HIGHLANDS ON WEDNESDAY. ELSEWHERE, AMOUNTS LOOK LIGHT  
GENERALLY 1 TO 3. TEMPERATURES WILL BE WARM ENOUGH IN THE MAGIC  
VALLEY FOR RAIN OR MAYBE A RAIN/SNOW MIX WITH NO ACCUMULATION.  
ALTHOUGH THE MAGIC VALLEY MAY NOT SEE MUCH OF ANYTHING WITH THE BULK  
OF THE SYSTEM FOCUSED ON THE EAST. PORTIONS OF THE MAGIC VALLEY AND  
LOWER SNAKE PLAIN WILL BE FLIRTING WITH WIND ADVISORIES ON  
WEDNESDAY. BLOWING AND DRIFTING SNOW WHERE SNOW DOES FALL MAY BE A  
PROBLEM AS WELL. WILL PROBABLY KEEP THE ADVISORIES "AS IS." NOT  
CONFIDENT ENOUGH THAT THERE WILL BE ENOUGH IMPACTS, SUCH AS ROAD  
CLOSURES, TO JUSTIFY AN UPGRADE TO A WARNING AT THIS TIME. THIS  
SYSTEM SHOULD DEPART THE REGION WEDNESDAY NIGHT, WITH SOME LINGERING  
LIGHT SNOW SHOWERS POSSIBLE FOR THURSDAY ACROSS THE EASTERN  
HIGHLANDS.  
 
VALLE  
 
LONG TERM...FRIDAY THROUGH NEXT TUESDAY.  
AT THIS EARLY VANTAGE POINT, WEATHER IN THE LONG-TERM PORTION OF THE  
FORECAST (FRI INTO THE UPCOMING WEEKEND AND EARLY NEXT WEEK) LOOKS  
FAIRLY LOW-IMPACT COMPARED TO THE SHORT-TERM. 12Z MODEL RUNS LOST  
SOME OF THEIR CONSENSUS WITH A SHORTWAVE TROUGH DIVING OVER THE  
CREST OF A PACIFIC RIDGE ON FRI. THE ECMWF REMAINS THE WETTEST BUT  
INITIATES SNOW SHOWER ACTIVITY BY FRI AM. GFS HOLDS OFF ON PRECIP  
UNTIL FRI AFTERNOON. THE CANADIAN IS LESS AMPLIFIED WITH THE TROUGH,  
BUT SEEMS TO FALL IN BETWEEN THE OTHER TWO. ALL THREE MODELS  
CONTINUE TO TARGET THE ISLAND PARK REGION, TETON VALLEY,  
EASTERN/CARIBOU HIGHLANDS, AND POSSIBLY THE BEAR RIVER RANGE, WITH  
LITTLE TO NO IMPACT WEST OF I-15 AND ONLY VERY LIGHT SNOW SHOWERS  
POSSIBLE IN THE CENTRAL MNTNS, SO THIS IS A GOOD/CONSISTENT SIGN.  
RAN WITH A BLEND OF THE PREVIOUS FORECAST WITH THE LATEST  
NBM/GFS/WPC GUIDANCE FOR POPS AND QPF AND NUDGED POPS SLIGHTLY  
HIGHER IN THE EASTERN HIGHLANDS/ISLAND PARK ZONE DESCRIBED ABOVE,  
BUT DIDN'T GO TOO HARDCORE HERE OVER THE BLEND PENDING BETTER MODEL  
CONSENSUS. OVERALL CONFIDENCE ON THIS ZONE BEARING THE BRUNT OF THE  
SYSTEM IS HIGH, BUT HOLDING WITH MODERATE CONFIDENCE IN THE REST OF  
THE DETAILS. ECMWF APPEARS TO BE AN OUTLIER AND FAR TOO HIGH ON QPF,  
WITH THE GFS, NAM, AND NBM ALL IN GOOD AGREEMENT. AN EARLY LOOK AT  
SNOWFALL FRI BASED ON FORECAST QPF/SNOW RATIOS YIELDS 1-2 INCHES IN  
THIS EASTERN ZONE WELL EAST OF I-15, WITH PERHAPS SOME LOCALIZED 3  
INCH AMOUNTS. A DUSTING IS POSSIBLE IN THE CENTRAL MNTNS.  
 
SAT AND MOST OF SUN CONT TO LOOK DRY ACROSS THE REGION WITH A BREAK  
BETWEEN SHORTWAVES AND NO SIGNIFICANT CHANGE IN TEMPS, ALTHOUGH  
THERE MAY BE SOME LOW STRATUS CLOUDS RUNNING AROUND IN PORTIONS OF  
THE SNAKE PLAIN E-NE INTO THE UPPER SNAKE HIGHLANDS AND EASTERN  
HIGHLANDS. POPS RAMP UP AGAIN BY SUN EVE ACROSS THE ISLAND PARK  
AREA, EXPANDING ACROSS THE CENTRAL MNTNS AND EASTERN HALF OF THE  
FORECAST AREA INTO MON AM. OVERALL THIS SECOND SHORTWAVE LOOKS A BIT  
STRONGER AND MORE MOIST THAN FRIDAY'S SYSTEM, AND MAY ALSO BRING  
BREEZY CONDITIONS TO THE REGION. (AN INCREASE OF 5-10 MPH IN  
ANTICIPATED WIND SPEEDS SUN NIGHT INTO MON EVE WAS NOTED IN GUIDANCE  
TODAY.) FOR NOW MODELS ARE IN VERY GOOD AGREEMENT ON THE PROGRESSION  
OF THIS SYSTEM, ALTHOUGH HAVE HELD POPS IN THE 20-50% RANGE THIS FAR  
OUT. THE COLD FRONT ASSOCIATED WITH THIS TROUGH WILL BRING A COLDER  
NORTHERLY FLOW MON AND TUES, WITH HIGHS BACKING OFF AT LEAST 5  
DEGREES AND LOWS FALLING INTO THE SINGLE DIGITS FOR MANY TUES AND  
WED MORNINGS, ASSUMING MOSTLY CLEAR SKIES. - KSMITH/VALLE  
 
AVIATION...SOME PERSISTENT LOW STRATUS HAS HELD IT'S GROUND  
TODAY IN SOUTHERN AND EASTERN PORTIONS OF THE SNAKE PLAIN,  
DROPPING KPIH TO IFR CIGS AND EVEN GRANTING KIDA A PERIOD OF  
FREEZING FOG. SATELLITE TRENDS SUGGEST THIS DECK IS BREAKING UP AS  
TEMPS CREEP UP AND INCREASE T/TD DEPRESSIONS, AND SOME UPPER-  
LEVEL CIRRUS WANDERS OVERHEAD. DO NOT BELIEVE THESE WOES WILL  
RETURN FOR THE REST OF THE AFTERNOON/EVE, BUT CONFIDENCE IS LOW.  
OUR ATTENTION THEN TURNS TO OUR NEXT STORM SYSTEM APPROACHING THE  
REGION LATE TONIGHT. TIMED OUT VCSH AND/OR - SHSN IN THE TAFS  
BASED ON A COMBINATION OF HIGH-RES HREF ENSEMBLE AND NAM TIME-  
HEIGHT PLOTS. GENERALLY EVERYONE IS EXPECTED TO REMAIN MVFR OR  
BETTER, EXCEPT KDIJ WHERE THERE IS A BETTER SIGNAL FOR LOW CLOUDS.  
OF COURSE, TRANSIENT PERIODS OF REDUCED VSBYS ARE POSSIBLE  
ANYWHERE A MODERATE SNOW SHOWER CAN PASS OVER A TERMINAL, WITH THE  
BEST CHANCE OF THIS AT KSUN, KIDA, AND KDIJ. WINDS WILL GRADUALLY  
BE ON THE INCREASE MON, AND LEFT IN LLWS REMARK FOR KIDA  
TONIGHT/WED. IF ANYTHING, WINDS AT 2,000 FEET MAY BE SLIGHTLY  
STRONGER HERE THAN CURRENTLY INDICATED...WILL LET THE NEXT SHIFT  
REEVALUATE AND UPDATE AS NECESSARY IN THE NEXT COUPLE TAFS  
PACKAGES. DECENT MIXING TO THE SURFACE REFLECTED IN MODEL GUIDANCE  
MAY HOLD THE MAGNITUDE OF LLWS AT BAY OVERALL WITH THIS SYSTEM. -  
KSMITH/VALLE  
 

 
   
PIH WATCHES/WARNINGS/ADVISORIES
 
 
WINTER WEATHER ADVISORY UNTIL 11 PM MST WEDNESDAY FOR IDZ062>066.  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab ID Page Main Text Page