Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 172010
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
210 PM MDT SUN AUG 17 2014

.DISCUSSION...UPPER LOW CENTERED NEAR SEATTLE THIS AFTERNOON PER
WV SAT IMAGERY. WEAK SHORTWAVE MOVING INTO SOUTHWEST IDAHO THIS
AFTERNOON HAS HELPED DEVELOP SOME WEAK BUILD UPS OVER PORTIONS OF
EAST IDAHO. GFS ON BOARD WITH NAM NOW IN DEVELOPING QPF FROM THESE
BUILD UPS FOR THIS EVENING AND CONTINUING PAST 06Z. PLACEMENT OF
QPF REMAINS IN LINE WITH PROGRESSION OF WEAK OREGON SHORTWAVE SO
WILL LEAVE LOW ISOLATED POPS IN PLACE. UPPER LOW OFF PACNW COAST
CONTINUES TO DIP SOUTH INTO MONDAY. RIDGE AXIS REMAINS OVER EAST
IDAHO BUT SIGNS OF MOISTURE SURGE PUSHES NORTH THROUGH GREAT
BASIN. BOTH MODELS MAINTAIN POCKETS OF MID LEVEL MOISTURE WITH NAM
STRONGEST IN PORTRAYING QPF DEVELOPMENT. WILL CONTINUE ISOLATED
CONVECTIVE POPS AFTERNOON/EVENING HIGHER ELEVATIONS. MUCH STRONGER
SIGNAL FOR STORMS TUESDAY AS UPPER LOW DIVES FURTHER SOUTH ALONG
COAST AND NORTHERN STREAM SHORTWAVE TROUGH PUSHES INTO CANADIAN
DIVIDE REGION. BELIEVE THIS TO BE BEST CHANCE OF CONVECTION IN
SHORT TERM AND HAVE AGAIN NUDGED POPS SLIGHTLY UPWARD ACROSS EAST
IDAHO. GUIDANCE ALSO SHOWING A DIP IN TEMPS FROM PREVIOUS RUNS
WITH INCREASED SURFACE DEWPTS AND POTENTIAL ADDITIONAL CLOUD COVER
EARLY. NAM MORE AGGRESSIVE IN KICKING BASE OF NORTHERN STREAM
TROUGH EAST OF ROCKIES TUESDAY NIGHT AND ALSO KEEPS SOUTHERN LOW
MORE CLOSED THAN GFS. RESULT IS THAT GFS MAINTAINS WETTER
CONDITIONS OVER EAST IDAHO TUESDAY NIGHT INTO EARLY WEDNESDAY.

SIMILAR DIFFERENCES APPARENT BETWEEN GFS AND ECMWF RUNS HEADING
BEYOND MID WEEK. BOTH MAINTAIN BROAD TROUGH OVER PACNW AND
NORTHERN MTNS BUT SLIGHT DIFFERENCES IN SHORTWAVE TIMING AND
OVERALL POSITION OF TROUGH AXIS. GFS A LITTLE SHARPER WITH TROUGH
EARLY IN THE EXTENDED AND SLIGHTLY WEST. REGARDLESS...BOTH MODELS
PAINT CONVECTION ACROSS EAST IDAHO EACH DAY WEDNESDAY THROUGH
FRIDAY. HEADING INTO WEEKEND...PRIOR RUNS THAT DEVELOPED DEEP CUT
OFF LOW OVER PACNW HAVE GIVEN WAY TO A MORE SHALLOW LOW CENTERED
FURTHER NORTHEAST. ADDITIONALLY...ECMWF HAS ABANDONED IDAHO OF CUT
OFF LOW OVERALL AND KEEPS BROAD TROUGH CONNECTED TO DEEP LOW IN
NORTHERN CANADA. BLENDED GUIDANCE TEMPS THROUGH THE WEEKEND WITH
ISOLATED POPS CLOSE TO CLIMO LEVELS. DMH


&&

.AVIATION...WE WILL SEE A SLIGHT INCREASE IN MOISTURE AND THE
POTENTIAL FOR ISOLATED MOUNTAIN STORMS ACROSS THE AREA. WE MAY SEE A
FEW STORMS AFFECT KBYI IN THE NEXT FEW HOURS. THE ONLY OTHER AIRPORT
THAT MIGHT BE AFFECTED BY STORMS IN THE NEXT 24 HOURS WOULD BE KSUN
TOMORROW AFTERNOON. VFR WEATHER IS FORECAST WITH GUSTY WINDS AND A
BRIEF DOWNPOUR POSSIBLE WITH ANY THUNDERSTORM ACTIVITY.  KEYES


&&

.FIRE WEATHER...WE WILL CONTINUE TO WATCH FOR THE INCREASING
POTENTIAL FOR SHOWERS AND THUNDERSTORMS THROUGH THE EARLY PART OF
THE WEEK. ISOLATED MOUNTAIN STORMS ARE POSSIBLE THROUGH THE NEXT 24
HOURS ESPECIALLY THROUGH THIS EVENING AND AGAIN TOMORROW AFTERNOON.
AFFECTED AREAS WOULD MAINLY BE PORTIONS OF THE CENTRAL MOUNTAINS AND
SOUTH-CENTRAL HIGHLANDS. AS THE STORM ALONG THE COAST CONTINUES TO
DEVELOP...A QUICK SURGE OF MONSOON MOISTURE WORKS NORTH. THE
QUESTION BECOMES WILL WE SEE THE FULL BRUNT OF IT OR GET CLIPPED AS
IT STREAMS INTO WYOMING. RIGHT NOW...WE ARE GOING FOR SOMETHING IN
BETWEEN. WE ARE FORECASTING ISOLATED/WIDELY SCATTERED STORMS FOR
TUESDAY ACROSS THE AREA. BRIEF DOWNPOURS AND GUSTY WINDS CAN BE
EXPECTED WITH ANY THUNDERSTORM DEVELOPMENT. FOR THE REST OF THE
WEEK...IT APPEARS THE SYSTEM FROM CANADA SAGS SOUTH INTO THE NORTHERN
U.S. WE ARE STILL LOOKING FOR A COOLDOWN ALONG WITH INCREASING
WINDS. SHOWERS AND STORMS ARE FORECAST ACROSS MOST AREAS. THE MODELS
ARE DIVERGING STILL WILDLY BY THE WEEKEND. THE ECMWF WANTS TO MOVE
THIS SYSTEM EASTWARD AND BRING COMPLETELY DRY WEATHER BY SUNDAY. THE
GFS HAS IT STILL HANGING AROUND WITH ONLY A SLIGHTLY EASTWARD
MOVEMENT...WITH SHOWERS AND STORMS POSSIBLE MAINLY NEAR THE DIVIDE.
BECAUSE OF THE EXTREME AMOUNT OF UNCERTAINTY PERSISTING...WE WILL
KEEP WITH THE PREVIOUS IDEA OF SOME SHOWERS AND STORMS WITH A LITTLE
BETTER CHANCE FARTHER NORTH. KEYES


&&

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

$$







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