Severe Thunderstorm Warning 84, NWS Pocatello, ID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
935 AM MDT SUN AUG 30 2009

.UPDATE...A FEW UPDATES TO GOING FCST THIS MORNING. CENTER OF
UPPER LOW NOW BETWEEN BOISE AND BAKER THIS MORNING. SHOWERS AND A
FEW THUNDERSTORMS SPREAD ACROSS CENTRAL MTNS. QUITE A BIT OF
CONVETIVE MID CLOUD OVER HIGHER TERRAIN REST OF AREA BUT GOOD
SUNSHINE SHOULD HELP DESTABILIZE AREA FOR LATER TODAY. NAM THIS
MORNING SHOWING BL CAPE VALUES BETWEEN 500 AND 1000 OVER MOST OF
THE AREA. HAVE ADJUSTED POP/WX/QPF GRIDS FOR TODAY...MAINLY TO
ADJUST FOR CURRENT SAT/RADAR TRENDS AND ADDITIONAL INSTABILTY FOR
THIS AFTERNOON AND EVENING. IN ADDITION...HAVE ADDED A FLASH FLOOD
WATCH FOR BLAINE FOR THE CASTLE ROCK FIRE THIS AFTERNOON AND
EVENING GIVEN PRECIPITABLE WATERS .7-.85. CENTER OF UPPER SHOULD
REACH CENTRAL MTNS OVERNIGHT TONIGHT AND WILL MAKE FURTHER
ADJUSTMENTS TO SHORT TERM PENDING TRACK OF SYSTEM AND CONVECTIVE
DEVELOPMENT. DMH

&&

.PREV DISCUSSION... /ISSUED 347 AM MDT SUN AUG 30 2009/

SHORT TERM...TODAY THROUGH TUESDAY.
UPPER LOW IN EASTERN OREGON AND WIDESPREAD SHOWERS AND
THUNDERSTORMS PERSISTED OVERNIGHT IN THE CENTRAL MOUNTAINS.
THROUGH LATE MORNING EXPECT THE CENTRAL MOUNTAINS AND UPPER SNAKE
RIVER HIGHLANDS TO CONTINUE TO RECEIVE SHOWERS AND THUNDERSTORMS
WITH THE MAJORITY OF THE REGION REMAINING DRY THROUGH THE MORNING.
WITH THE INSTABILITY PUSHING EAST AS THE LOW MOVES EAST EXPECT
SCATTERED THUNDERSTORMS EVERYWHERE THIS AFTERNOON WITH CATEGORICAL
PRECIPITATION CHANCES CONTINUING IN THE CENTRAL MOUNTAINS. AS THE
UPPER LOW PUSHES THROUGH SOUTHERN IDAHO OVERNIGHT EXPECT THE BRUNT
OF THE SHOWER ACTIVITY TO PUSH EAST INTO THE SNAKE PLAIN AND UPPER
SNAKE HIGHLANDS WITH WRAP AROUND MOISTURE AND INSTABILITY KEEPING
THE CHANCE OF THUNDERSTORMS GOING THROUGH MONDAY. LOW PUSHES INTO
SOUTHERN MONTANA MONDAY NIGHT AND EXPECT MAINLY DRY WEATHER ON
TUESDAY WITH AN UPPER RIDGE REPLACING THE LOW.
GK

LONG TERM...WEDNESDAY THROUGH NEXT SUNDAY.
UPPER RIDGE OVERHEAD THROUGH WEDNESDAY AND PUSHES EAST THURSDAY.
GFS BRINGS IN NEXT PACIFIC TROF FRIDAY AND COULD SEE A CHANCE OF
SHOWERS AND THUNDERSTORMS AS THE TROF PUSHES EAST THURSDAY INTO
NEXT SUNDAY. SOME SLIGHT TIMING DIFFERENCES ON EUROPEAN AND GFS
MODELS BUT DID NOT GET TOO CUTE WITH THE GRID DEPICTION OF WEATHER
AND KEPT THE THREAT GOING MAINLY IN THE FRIDAY TO SUNDAY PERIOD IN
THE EXTENDED PORTION OF THE FORECAST.
GK

AVIATION...A STRONG LOW PRESSURE SYSTEM POSITIONED OVER NE OREGON
THIS MORNING WAS PRODUCING NUMEROUS THUNDERSTORMS ACROSS THE CNTRL
MOUNTAINS. THE LOW IS EXPECTED TO PROGRESS ESE THROUGH BOISE BEFORE
LIFTING ENE INTO ARCO BY MONDAY MORNING. SUFFICIENT DYNAMICS AND
INSTABILITY WILL ACCOMPANY THE LOW TO PRODUCE NUMEROUS THUNDERSTORMS
THROUGHOUT THE NEXT 24 HOURS. WIDESPREAD VFR CONDITIONS ARE EXPECTED
UNDER MID-LEVEL CLOUD COVER WITH SCT MVFR CIGS IN THUNDERSHOWERS AND
TEMPORARY IFR VISIBILITY IN SHOWERS FOCUSED NEAR KSUN THIS MORNING
AND THEN POTENTIALLY SPREADING INTO THE SNAKE RIVER PLAIN
(KBYI/KPIH/KIDA) BY THIS AFTERNOON/EVE. HUSTON

FIRE WEATHER...A STRONG LOW PRESSURE SYSTEM POSITIONED OVER NE
OREGON EARLY THIS MORNING WAS PRODUCING NUMEROUS THUNDERSTORMS
ACROSS THE CNTRL MOUNTAINS. THE LOW IS EXPECTED TO GRADUALLY MIGRATE
ESE TO BOISE THIS AFTERNOON AND THEN ENE TO ARCO BY MONDAY MORNING
WITH NUMEROUS THUNDERSTORMS ADVANCING OUT AHEAD OF THE LOW.
WIDESPREAD SHOWERS...POTENTIALLY HEAVY AT TIMES WILL ACCOMPANY THE
THUNDERSTORMS ACROSS THE FORECAST AREA. CRITICAL FUELS BELOW 4500
FEET WERE INDICATED FOR ZONES 409 AND 412...THUS A RED FLAG WARNING
WILL BE ISSUED FOR THOSE ZONES FOR THIS AFTERNOON AND EVENING. BY
LATE MONDAY AFTERNOON...THE LOW IS EXPECTED TO LIFT NE INTO
YELLOWSTONE NP AND THEN ACCELERATE EAST THROUGH SRN MONTANA
OVERNIGHT WITH DRIER CONDITIONS OVERSPREADING SRN IDAHO AS A RIDGE
OF HIGH PRESSURE REBOUNDS ACROSS THE AREA. OUR TWO EXTENDED MODELS
ARE SHOWING CONSIDERABLE DISAGREEMENT ON THE EVOLUTION AND SPEED OF
THE NEXT INCOMING PACIFIC STORM SYSTEM...AT THE EARLIEST WE COULD
SEE MORE THUNDERSTORM ACTIVITY BY THURSDAY AFTERNOON OR AT THE
LATEST NEXT SATURDAY. HUSTON

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING FROM 3 PM THIS AFTERNOON TO MIDNIGHT MDT
TONIGHT FOR IDZ409-412.

FLASH FLOOD WATCH FROM 3 PM MDT THIS AFTERNOON THROUGH THIS
EVENING FOR IDZ031.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE POCATELLO ID
530 AM MDT SUN AUG 30 2009

IDZ017>025-031-032-311300-
EASTERN MAGIC VALLEY-SAWTOOTH MOUNTAINS-UPPER SNAKE HIGHLANDS-
UPPER SNAKE RIVER PLAIN-LOWER SNAKE RIVER PLAIN-
SOUTH CENTRAL HIGHLANDS-CARIBOU HIGHLANDS-
CACHE VALLEY/IDAHO PORTION-WASATCH MOUNTAINS/IDAHO PORTION-
BIG AND LITTLE WOOD RIVER REGION-LOST RIVER/PAHSIMEROI-
530 AM MDT SUN AUG 30 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN IDAHO.

.DAY ONE...TODAY AND TONIGHT

SHOWERS AND THUNDERSTORMS TODAY AND TONIGHT.  A RED FLAG WARNING IS
IN EFFECT FOR FIRE WEATHER ZONES 409 AND 412 FOR THUNDERSTORMS.  SEE
LATEST BOIRFWPIH FOR DETAILS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

HAZARDOUS WEATHER IS NOT EXPECTED.

.SPOTTER INFORMATION STATEMENT...

WE ASK TRAINED SPOTTERS AND CITIZENS TO REPORT SIGNIFICANT
WEATHER CONDITIONS WHEN IT IS SAFE TO DO SO. THESE CONDITIONS MAY
INCLUDE HAIL...TORNADOES...STRONG WIND...DUST STORMS...SNOWFALL...
EXTREME COLD TEMPERATURES...FREEZING RAIN OR HEAVY RAIN...DENSE
FOG...AND FLOODING OR ICE JAMS. INFORMATION ABOUT THESE HAZARDOUS
CONDITIONS SHOULD BE CALLED INTO YOUR NATIONAL WEATHER SERVICE
OFFICE IN POCATELLO USING THE 1-800 SEVERE WEATHER HOTLINE...OR
208-233-0834.