Flash Flood in Idaho, August 23, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
147 PM MDT FRI AUG 23 2013

.SHORT TERM...TONIGHT THROUGH SUNDAY. MOISTURE ASSOCIATED WITH THE
MONSOON CONTINUES TO STREAM INTO SOUTHEAST IDAHO. AN EMBEDDED
DISTURBANCE OVER CENTRAL UTAH AND NEVADA THIS AFTERNOON IS
ROTATING TOWARDS THE SOUTH CENTRAL HIGHLANDS WHERE THUNDERSTORMS
ARE ALREADY DEVELOPING. SHOWERS SHOULD CONTINUE NORTHEAST TOWARDS
ISLAND PARK THROUGH EARLY SATURDAY MORNING. BY SATURDAY AFTERNOON
A NEW DISTURBANCE DROPS INTO THE BASE OF THE LOW PRESSURE TROUGH
JUST OFF SHORE THEN LIFTS SHARPLY NORTHEAST THROUGH OREGON. THIS
SHOULD BACK THE FLOW PATTERN TO THE SOUTH AND FOCUS SHOWERS AND
THUNDERSTORMS SATURDAY AFTERNOON INTO THE CENTRAL MOUNTAINS. THE
GFS REPEATS THIS PATTERN AGAIN ON SUNDAY.

.LONG TERM...MONDAY THROUGH THURSDAY. THERE APPEARS TO BE LITTLE
CHANGE IN THE PATTERN. HIGH PRESSURE RIDGE REMAINS OVER KANSAS
WITH A TROUGH NEAR THE WEST COAST. THIS CONTINUES TO FUNNEL MOIST
AIR NORTH THROUGH THE GREAT BASIN. FORECAST CHALLENGE MAY HINGE ON
TROPICAL DISTURBANCES CROSSING CENTRAL AMERICA AND MEXICO.
TROPICAL STORM IVO IS PRESENTLY NEAR THE TIP OF BAJA
CALIFORNIA...ONCE THE STORM RECUREVS NORTH ALONG THE COAST THE
MOIST AIR COULD SURGE THROUGH THE GREAT BASIN OVER A 24 HOUR
PERIOD. THE GFS CURRENTLY TRIES TO DO THIS BETWEEN SUNDAY MORNING
AND MONDAY MORNING....TRACKING THE DEEPER MOISTURE ROUGHLY THROUGH
EVANSTON WYOMING. SOUTHEAST IDAHO MAY CATCH PART OF THE ACTION OR
GET LEFT IN DRIER AIR JUST TO THE WEST. INTERESTING ENOUGH...THE
EXTENDED MODEL SHOW AGREEMENT AND MUSTER UP ANOTHER TROPICAL
DISTURBANCE CROSSING CENTRAL AMERICA BY NEXT FRIDAY. RS

&&

.AVIATION...EXPECT THUNDERSTORM DEVELOPMENT AGAIN THIS AFTERNOON
WITH VICINITY THUNDERSTORMS AT ALL SITES.  MOST LIKELY FOR ON
STATION THUNDER WOULD BE PIH AND IDA.  MOIST SOUTHERLY FLOW ALOFT
CONTINUES SATURDAY AND EXPECT AFTERNOON THUNDERSTORM DEVELOPMENT
AGAIN.  VFR CONDITIONS SHOULD CONTINUE THROUGH THE PERIOD OUTSIDE OF
THE THUNDERSTORMS.
GK

&&

.FIRE WEATHER...MOIST SOUTHERLY FLOW CONTINUES OVER THE DISTRICT.
RED FLAG WARNINGS IN EFFECT FOR SCATTERED THUNDERSTORMS FOR ZONES
475...476...410...413...AND 427.  SOME SLIGHTLY DRIER AIR PUSHING
INTO WESTERN PORTION OF DISTRICT.  ALL LOCATIONS WILL HAVE AT LEAST
ISOLATED COVERAGE THIS EVENING.  SIMILAR CONDITIONS ARE EXPECTED
SATURDAY AND SUNDAY WITH THE MOIST SOUTHERLY FLOW CONTINUING AND
FURTHER RED FLAG WARNINGS FOR THUNDERSTORMS WILL LIKELY BE NEEDED.
WITH THE MOIST PATTERN MINIMUM HUMIDITY SHOULD STAY WELL ABOVE 15
PERCENT THROUGH THE WEEKEND.
GK

.PIH WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 10 PM MDT THIS EVENING
IDZ410-413-427-475-476.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE POCATELLO ID
418 AM MDT FRI AUG 23 2013

IDZ017>025-031-032-241030-
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-
418 AM MDT FRI AUG 23 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN IDAHO.

.DAY ONE...TODAY AND TONIGHT

SHOWERS AND THUNDERSTORMS WILL CONTINUE...ESPECIALLY IN THE
AFTERNOON AND EARLY EVENING. THE BEST CHANCE WILL BE EAST OF A
CHALLIS-CAREY-CITY OF ROCKS LINE. STORMS WILL BE CAPABLE OF
PRODUCING WINDS OVER 40MPH...SMALL HAIL AND LOCALLY HEAVY
RAINFALL. THE POTENTIAL IS THERE FOR LOCALIZED FLOODING OR DEBRIS
FLOWS WITHIN RECENT BURN AREAS AND STEEP TERRAIN. THE THREAT FOR
SEVERE STORMS IS LOW...BUT NON-ZERO.

DUE TO THE THREAT OF WIDELY SCATTERED TO SCATTERED THUNDERSTORMS
AND GUSTY DOWNBURST WINDS...RED FLAG WARNINGS HAVE BEEN POSTED FOR
ALL FIRE ZONES EXCEPT ZONE 422 AND 425. THESE ARE IN EFFECT FROM
NOON THROUGH 10PM.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

MOISTURE WILL CONTINUE TO STREAM NORTHEAST ACROSS THE WESTERN
STATES. THERE IS SOME UNCERTAINTY ON WHERE THIS SURGE OF MOISTURE
WILL LIE ACROSS THE WEST...INCLUDING EASTERN IDAHO. WITHIN THIS
SURGE OF MOISTURE...IT WILL BE VERY DEEP AS IT WILL BE
SUPPLEMENTED BY ONE OR TWO TROPICAL STORMS. THIS MEANS PLENTY OF
RAINFALL...AND POSSIBLY TOO MUCH. JUST TO THE WEST OF THIS
AREA...THERE WILL BE A VERY STRONG DRY SLOT AND BREEZY CONDITIONS
FOR A PROLONGED PERIOD.

THIS APPEARS TO BE A LONG DURATION PATTERN...WHICH WILL AFFECT
MANY DIFFERENT GROUPS AND LAST INTO THE LABOR DAY WEEKEND MOST
LIKELY. STAY TUNED IN THE COMING DAYS TO SEE HOW THIS SITUATION
EVOLVES.

.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.