000
FXUS65 KPIH 181536
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
936 AM MDT SAT MAY 18 2013

.UPDATE...

UPDATED FORECAST TO ISSUE A LAKE WIND ADVISORY FOR THE AMERICAN
FALLS RESERVOIR. OBSERVATIONS THE PAST COUPLE OF HOURS HAVE SHOWN
WIND SPEEDS NEAR 20 MPH. EXPECT WINDS TO REMAIN NEAR THIS SPEED
THROUGH THE AFTERNOON AND EARLY EVENING. MADE SOME MINOR
ADJUSTMENTS TO SKY AND PRECIPITATION CHANCES FOR THE AFTERNOON AND
TONIGHT AS WELL. STILL LOOKS RATHER UNSETTLED ACROSS THE REGION
TODAY...ESPECIALLY OVER THE EASTERN HIGHLANDS.

VALLE

&&

.PREV DISCUSSION... /ISSUED 311 AM MDT SAT MAY 18 2013/

DISCUSSION...SAT IMAGERY SHOWS COMPLEX UPPER TROUGH SWINGING
THROUGH THE REGION THIS MORNING. MAIN CIRCULATION CENTER OVER
NORTHWEST UTAH THIS MORNING...WITH LARGE SWATH OF PRECIPITATION
EXTENDING NORTH INTO SOUTHEAST CORNER OF EASTERN IDAHO PER RADAR
IMAGERY. NEXT CIRCULATION OF INTEREST IN NORTHEAST OREGON WITH
SMALLER AND WEAKER AREA OF PRECIPITATION ASSOCIATED WITH IT.
MODELS SWING TROUGH NORTHEAST THIS MORNING WITH NEGATIVE TILT.
AIRMASS BECOMES WEAKLY UNSTABLE BY 18Z OVER MOST OF THE REGION SO
HAVE MAINTAINED HIGH POP GRIDS THROUGH THE DAY WITH ISOLATED
THUNDER INTO THE AFTERNOON. EASTERN IDAHO REMAINS UNDER THE
INFLUENCE OF CYCLONIC FLOW WITH NEXT STRONGER SHORTWAVE ALREADY
ALONG THE OREGON COAST THIS MORNING PROGGED TO REACH THE REGION
OVERNIGHT TONIGHT. MODELS NOT QUITE IN AGREEMENT ON BEST LOCATION
FOR DEVELOPMENT THIS EVENING INTO SUNDAY THUS BROADBRUSHED LIGHT
CHANCE POPS WITH SLIGHT SNAKE PLAIN. TROUGH DEEPENS INTO CLOSED
LOW OVER THE GREAT PLAINS BY MONDAY WITH ONLY LINGERING LIGHT
SHOWERS ALONG THE EASTERN HIGHLANDS AS RIDGE BEGINS TO BUILD INTO
THE PACNW.

RIDGE SHORTLIVED IN THE AMPLIFIED BUT PROGRESSIVE FLOW WITH NEXT
PACIFIC TROUGH REACHING THE COAST DURING THE DAY TUESDAY. BOTH GFS
AND ECMWF AGREE ON DEVELOPMENT OF THIS NEXT LARGE LOW OVER THE
REGION THROUGH THE LATTER HALF OF THE WEEK THOUGH GFS KEEPS THE
CENTER OF THE LOW SLIGHTLY FURTHER NORTH THAN THE ECMWF. INTERESTINGLY
BOTH MODELS ALSO MAINTAIN A LARGE DRY SLOT CENTERED OVER EASTERN
IDAHO WITH PRECIP PUSHED MAINLY NORTH OF THE AREA. GIVEN THE DEPTH
OF THE LOW...OPTED TO MAINTAIN WEAK POPS MOST AREAS THROUGH THE
WEEK. DMH

AVIATION...RAIN AND CONVECTIVE SHOWERS EXPECTED FROM PIH TO IDA AND
AREAS EASTWARD TODAY.  MVFR POSSIBLE NEAR CONVECTIVE SHOWERS THIS
AFTERNOON WHILE VFR FOR REST OF THE AREA.  GUSTY SOUTHWEST WINDS ARE
EXPECTED BY THIS AFTERNOON FROM THE SOUTHWEST IN THE SNAKE RIVER
PLAIN.  PRESTON

FIRE WEATHER...NUMEROUS RAIN SHOWERS ARE POSSIBLE IN THE SOUTHEAST
CORNER TODAY WITH WETTING RAINS AS AS AN UPPER TROUGH MOVES THROUGH
THE AREA.   ISOLATED AFTERNOON CONVECTIVE SHOWERS ARE POSSIBLE IN
UNSTABLE AIR OVER ALL THE AREA THIS AFTERNOON.  BEHIND THIS EXITING
SYSTEM GUSTY SOUTHWEST WINDS WILL DEVELOP IN THE SNAKE RIVER PLAIN
BY THIS AFTERNOON.  A SECOND SHOT OF ENERGY WILL DEVELOP ON SUNDAY
WITH MORE SHOWERS POSSIBLE.  DRY CONDITIONS AND WARMER TEMPS ARE
EXPECTED ON MON AND TUE AS UPPER RIDGING MOVES INTO THE NW. A DEEP
UPPER LOW IS EXPECTED TO MOVE INTO THE PAC NW BY WEDNESDAY...HOWEVER
CURRENT MODEL TRENDS KEEP OUR AREA IN THE WARM SECTOR WITH A FEW
AFTERNOON THUNDERSTORMS POSSIBLE ESPECIALLY IN THE CENTRAL IDAHO
MOUNTAINS THROUGH THE LATER PART OF THE WEEK.  PRESTON

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY UNTIL 9 PM MDT THIS EVENING IDZ021.

&&

$$