428  
FXUS65 KPIH 152027  
AFDPIH  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE POCATELLO ID  
227 PM MDT WED AUG 15 2018  
   
SHORT TERM
 
TODAY THROUGH FRIDAY. DRY AIR CLEARLY EVIDENT ON WV  
IMAGERY HOLDS IT'S GRIP ON THE AREA, SHUNTING DEEPER MOISTURE  
SOUTH OF THE FORECAST AREA. NORTHEAST NEVADA WILL BE THE FOCUS FOR  
EVENING CONVECTION AS A SHORTWAVE TROUGH TRIES TO PUSH THIS  
DEEPER MOISTURE NORTHWARD. WILL CREEP MENTION OF ISOLATED SHOWERS  
AND THUNDERSTORMS INTO SOUTHWESTERN CASSIA BUT DURATION AND  
IMPACTS SHOULD BE RATHER LOW TONIGHT.  
 
BY THURSDAY, THE DEEPER MOISTURE WILL OOZE INTO OUR SOUTHERN  
ZONES, AND WRAP AROUND THE NORTHERN PERIPHERY OF THE RIDGE AND  
INTO THE CENTRAL MOUNTAINS AS ANOTHER SHORTWAVE ROUNDS THE ERODING  
RIDGE. THIS WILL LEAD TO AN INCREASE IN SHOWER AND THUNDERSTORM  
ACTIVITY IN THESE LOCATIONS. OPTED TO LIMIT T-STORM POTENTIAL TO  
ISOLATED THROUGH THE CENTRAL MOUNTAINS AND GO SCATTERED ACROSS OUR  
SOUTHWEST. THIS WILL NECESSITATE A FIRE WEATHER WATCH FOR ZONE  
427 BEGINNING AT NOON THURSDAY.  
 
A DEEPER LOW PRESSURE SYSTEM ARRIVES FRIDAY, BRINGING THE BEST  
CHANCE FOR SHOWERS AND THUNDERSTORMS THAN WE'VE SEEN IN QUITE SOME  
TIME. THE UPPER-LEVEL LOW BEGINS TO OPEN TO A WAVE AS IT  
APPROACHES, WEAKENING THE UPPER-LEVEL WIND FIELD. EVEN STILL, THE  
JET AROUND THE SOUTHEASTERN PERIPHERY OF THE LOW WILL FUEL UPPER-  
LEVEL DIVERGENCE ENTERING THE FORECAST AREA FRIDAY  
AFTERNOON/EVENING. SCATTERED SHOWERS AND THUNDERSTORMS ARE  
EXPECTED AREAWIDE, BUT THE BEST CHANCE LOOKS TO BE ALONG THE  
NORTHEAST QUADRANT OF THE LOW, NEAR THE MONTANA/IDAHO LINE. WHILE  
CAPE VALUES ARE PROGGED TO BE FAIRLY LOW, STEEP LAPSE RATES AND  
INVERTED-V SOUNDINGS BRING THE POTENTIAL FOR STRONG GUSTY SHOWERS  
AND THUNDERSTORMS. THIS, ALONG WITH POTENTIAL FOR SCATTERED  
LIGHTNING, MEANS A FIRE WEATHER WATCH WILL ALSO BE NEEDED FOR MOST  
LOCATIONS THROUGH FRIDAY EVENING.  
   
LONG TERM
 
SATURDAY THROUGH WEDNESDAY. THE BULK OF SHOWERS AND  
THUNDERSTORMS WILL PASS THROUGH FRIDAY EVENING/NIGHT, BUT  
SCATTERED SHOWERS WILL CONTINUE TO LINGER INTO SATURDAY FOR THE  
UPPER SNAKE PLAIN AS THE LOW CRUISES EAST OF THE AREA. IN THE WAKE  
OF THIS SYSTEM THE FORECAST WILL TREND DRIER AS THE MOISTURE  
EVACUATES UNDER INCREASINGLY ZONAL FLOW EARLY NEXT WEEK.  
OPERATIONAL MODELS THEN TRY TO DEVELOP ANOTHER DISTURBANCE ACROSS  
THE NORTHWEST MIDDLE OF NEXT WEEK WHICH TRIES TO REINVIGORATE  
SHOWER CHANCES, BUT THE ENSEMBLES TEND TO FAVOR A DRIER FORECAST.  
WILL CONTINUE TO CARRY DRY IN THE FORECAST DURING THIS TIME OF  
UNCERTAINTY IN THE EXTENDED.  
 
TAX  
 

 
   
AVIATION
 
VFR CONDITIONS ALONG WITH RELATIVELY LIGHT WINDS WILL  
CONTINUE THIS AFTERNOON THROUGH TOMORROW AS OUR AREA REMAINS UNDER  
HIGH PRESSURE. MOISTURE WILL WORK ITS WAY INTO THE AREA FROM THE  
SOUTH AND WEST THURSDAY AFTERNOON ALLOWING FOR THUNDERSTORMS  
DEVELOPMENT. EXPECT MORE WIDESPREAD PRECIPITATION AND THUNDERSTORMS  
FRIDAY AS A SYSTEM MOVE THROUGH.  
 
WYATT  
 

 
   
FIRE WEATHER
 
WINDS WILL BE LIGHTER TODAY FOR MOST LOCATIONS, BUT  
VERY DRY AIR AT THE SURFACE REMAINS IN PLACE. THE HAINES INDEX IS 6  
ACROSS MUCH OF THE AREA THIS AFTERNOON IMPROVING SLIGHTLY THIS  
EVENING TO 5 BEFORE DROPPING OFF SIGNIFICANTLY BY FRIDAY. LIMITED  
MONSOON MOISTURE IS CREEPING NORTH AND EAST CURRENTLY. SOME MODELS  
ARE STILL TRYING TO KICK OFF VERY ISOLATED THUNDERSTORMS FROM AROUND  
CITY OF ROCKS WEST ALONG THE UTAH AND NEVADA BORDERS. GUSTY WINDS  
OVER 30 MPH ARE POSSIBLE AND COULD MOVE INTO THE AREA FROM UTAH AND  
NEVADA. MONSOON MOISTURE CONTINUES TO DRIFT NORTHEAST TONIGHT AND  
THURSDAY. WE MIGHT SEE VIRGA OR A DRY STORM OVERNIGHT ACROSS THE THE  
SOUTHERN HIGHLANDS SOUTH OF BURLEY, BUT THE RISK IS VERY LOW.  
DESPITE HIGHER LEVELS OF MOISTURE EXPECT POOR HUMIDITY RECOVERY  
OVERNIGHT SIMILAR TO LAST NIGHT. THURSDAY LOOK FOR A SLIGHTLY BETTER  
CHANCE FOR DRY THUNDERSTORMS ACROSS ALL OF CENTRAL AND EASTERN IDAHO  
, BUT STILL LOOKING AT ISOLATED/WIDELY SCATTERED COVERAGE. AFTERNOON  
RELATIVE HUMIDITY CLIMBS BUT STILL ONLY IN THE TEENS. FRIDAY LOOKS  
TO BE VERY ACTIVE STARTING IN WESTERN ZONES IN THE AFTERNOON,  
SPREADING EAST IN THE EVENING AND OVERNIGHT AS AN UPPER LEVEL LOW  
SYSTEM MOVES THROUGH THE AREA. A FIRE WEATHER WATCH FOR  
THUNDERSTORMS IS CURRENTLY IN EFFECT FOR ALL FIRE WEATHER ZONES  
EXCEPT ZONE 411 WHERE FUELS STILL REMAIN BELOW CRITICAL VALUES.  
THERE WILL LIKELY BE A MIX OF WET AND DRY STORMS, WITH STRONGER  
STORMS BRINGING THE BEST CHANCE OF WETTING RAINS. THIS LOW SHIFTS  
EAST SATURDAY, WITH SOME WRAP-AROUND SHOWERS AND STORMS ALONG THE  
MONTANA DIVIDE AND EAST OF I-15 BY AFTERNOON. THE MODELS ARE TRYING  
TO RETURN ANOTHER RIDGE SETTING UP OVER THE WEST LATER SATURDAY INTO  
SUNDAY. THERE IS A LOT OF UNCERTAINTY PAST THIS POINT, BUT MODELS  
ARE HINTING TO ANOTHER UPPER LEVEL LOW WORKING INTO OUR AREA.  
HOWEVER, MODELS SHOW LIMITED MOISTURE ASSOCIATED WITH THIS SYSTEM AT  
THIS POINT.  
 
WYATT  
 

 
   
PIH WATCHES/WARNINGS/ADVISORIES
 
 
FIRE WEATHER WATCH FROM FRIDAY AFTERNOON THROUGH FRIDAY EVENING  
FOR IDZ410-413-422-425-475-476.  
 
FIRE WEATHER WATCH FROM THURSDAY AFTERNOON THROUGH FRIDAY  
EVENING FOR IDZ427.  
 

 
 

 
 
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