Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 310849
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
249 AM MDT SUN AUG 31 2014

.SHORT TERM...TODAY THROUGH TUE NIGHT. LAST ROUND OF SHOWERS AND
THUNDERSTORMS IS OVER THE NEXT 24 HOURS. ANOTHER UPPER LEVEL TROUGH
IS MOVING THROUGH THE FORECAST AREA THIS MORNING. THIS WILL KEEP
THE WIND ELEVATED DURING THE MORNING...AND ITS MOVING AWAY WILL
CAUSE A WEAKENING OF THE WIND DURING THE AFTERNOON. WIND IS ONCE
AGAIN STRONG ENOUGH OVER THE RESERVOIR TO MEAN A LAKE WIND
ADVISORY THERE...BUT FOR THE LATE MORNING AND EARLY AFTERNOON. SHOWERS
AND THUNDERSTORMS WILL CLEAR FROM WEST TO EAST DURING THE
AFTERNOON AS WELL. BY LATE TONIGHT...SKIES WILL CLEAR AND LOW
TEMPERATURES WILL PLUMMET FROM THE RECENT MILD FIGURES TO MORE
CLIMATIC AVERAGES. HIGH PRESSURE WILL DOMINATE THE WEATHER FOR THE
HOLIDAY AND BEYOND INTO THE EXTENDED PERIOD. TEMPERATURES WILL BE
SLOW TO WARM AT FIRST...BUT BETWEEN MON AND TUE SHOULD WARM
STRONGLY...BACK TO NEAR NORMAL. IN FACT TEMPERATURES WILL THE MOST
DIFFICULT ITEM TO FORECAST. SREF BIAS- CORRECTED GUIDANCE WAS
INDICATING MUCH COLDER TEMPERATURES THAN THE GFS OR NAM MOS
OUTPUT...AND HAD TO MODIFY IT AGAINST NEIGHBORS AS WELL TO MEET
COORDINATION THRESHOLDS. THIS MOSTLY BECAUSE THE NAM IS MUCH
COLDER THAN THE GFS...AND THEN THROW IN AN APPARENT WARM BIAS TO
GUIDANCE LATELY. THIS PROBLEM CONTINUES INTO THE LONG TERM.

.LONG TERM...WED THROUGH SAT NIGHT. VERY DRY EARLY IN THIS
PERIOD...BUT THE UPPER LEVEL RIDGE THAT ALLOWS A WARMING AND
DRYING HAS BEEN EXPECTED TO BREAK DOWN ON THU FOR THE LAST COUPLE
OF DAYS. HOWEVER...THE GFS HAS...IN AN UNCHARACTERISTIC
SOLUTION...SLOWED THE APPROACH OF THIS NEXT TROUGH COMPARED TO THE
ECMWF. NCEP NOTED THAT THE GFS ENSEMBLE MORE CLOSELY MATCHED THE
ECMWF. THE ECMWF SWEEPS A TROUGH THROUGH DURING THE THU/THU
NIGHT/FRI TIMEFRAME...BUT IT IS QUITE DRY. THE GFS KEEPS THE
TROUGH AWAY...AND SO WE STAY MUCH WARMER. NEITHER SOLUTION APPEARS
CORRECT AS THE BEHAVIOR OF THIS NEXT UPSTREAM WAVE IS ODD BASED ON
EXPERIENCE. SO THERE IS A WIDE DISCREPANCY MAINLY SEEN IN
TEMPERATURES...NOT ONLY AMONG GUIDANCE PRODUCTS BUT ALSO WITH
SURROUNDING OFFICES PICKING DIFFERENT SOLUTIONS. ALL OF THIS MAKES
FOR A LOW-CONFIDENCE FORECAST FOR THU AND BEYOND...ESPECIALLY
TEMPERATURES. WHEN IT COMES TO SKY/POP/WEATHER...HAVE PAINTED WITH A
VERY BROAD BRUSH FOR THIS SECOND HALF. DID NOT GO WITH THE VERY
DRY AND OUTLYING GFS SCENARIO...LEFT SOME LOW CHANCE/CHANCE POPS
IN FOR THIS PERIOD. MESSICK

&&

.AVIATION...SHOWERS AND ISOLD TSTMS WILL CONTINUE EARLY THIS MORNING
AS THE UPPER TROF OVER ID THIS MORNING MOVES TO THE EAST TODAY. THIS
WILL SHIFT MOST OF THE PRECIP TO THE EASTERN HIGHLANDS AND UPPER
SNAKE HIGHLANDS BY LATE MORNING. ISOLD SHOWERS STILL REMAIN POSSIBLE
THIS EVENING IN THE UPPER SNAKE HIGHLANDS. OTHERWISE...VFR
CONDITIONS WILL PREVAIL. HEDGES

&&

.FIRE WEATHER...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS THIS
MORNING WILL MOVE TO THE EASTERN AND UPPER SNAKE HIGHLANDS BY
AFTERNOON AS THE UPPER TROUGH OVER IDAHO MOVES TO THE EAST. THE
REGION IS EXPECTED TO REMAIN DRY INTO NEXT WEEK AS NORTHWEST FLOW
ALOFT BECOMES DOMINANT. TEMPERATURES WILL REMAIN COOL THROUGH
MONDAY...BUT WARM BACK UP TUESDAY AND WEDNESDAY. ANOTHER COLD FRONT
IS EXPECTED TO PASS THROUGH IDAHO ON WEDNESDAY...BUT IT APPEARS TO
BE MAINLY DRY. HEDGES

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
LAKE WIND ADVISORY FROM 9 AM THIS MORNING TO 3 PM MDT THIS
AFTERNOON IDZ021.

&&

$$






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