Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 050252
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
852 PM MDT FRI SEP 4 2015

.UPDATE...DID A QUICK UPDATE THIS EVENING TO MORE CLOSELY MATCH
FORECAST GRIDS WITH OBSERVATIONAL AND MODEL TRENDS. MID LEVEL
FRONTAL CIRCULATION HAS SET UP OVER THE AREA...AND THIS COMBINED
WITH ADEQUATE MOISTURE AND JET DYNAMICS IN ASSOCIATION WITH A DEEP
CLOSED LOW OVER THE PACNW HAS RESULTED IN AN INCREASE IN
PRECIPITATION OVER THE EASTERN HIGHLANDS AND PORTIONS OF THE
CENTRAL MOUNTAINS. THIS COMBINED WITH A DOWNWARD NUDGE IN SNOW
LEVELS ACROSS THE CENTRAL MOUNTAINS RESULTED IN A SLIGHT UPTICK
IN EXPECTED SNOWFALL TOTALS OVERNIGHT...THOUGH WITH NO
SIGNIFICANT CHANGE IN ANTICIPATED IMPACTS. A FEW STRONG
THUNDERSTORMS WILL CONTINUE OVER THE EASTERN HIGHLANDS FOR THE
NEXT SEVERAL HOURS...WITH THE MAIN IMPACT BEING GUSTY WINDS. AD


&&

&&

.PREV DISCUSSION... /ISSUED 149 PM MDT FRI SEP 4 2015/

SHORT TERM...ELONGATED CLOSED LOW CURRENTLY EXTENDS FROM SOUTHERN
BRITISH COLOMBIA SOUTHWARD THROUGH OREGON. THIS LOW WILL GRADUALLY
WOBBLE EASTWARD THROUGH TOMORROW BEFORE RAPIDLY LIFTING OUT OF THE
REGION ON SUNDAY. THIS IS AN ANOMALOUSLY DEEP LOW FOR THIS TIME
OF YEAR...WITH 500MB HEIGHTS AND TEMPS PROGGED TO BE AROUND THREE
STANDARD DEVIATIONS BELOW CLIMATOLOGY. WHAT THIS MEANS IN TERMS OF
SENSIBLE WEATHER IMPACTS IS THAT TEMPERATURES WILL BE 10 TO 20
DEGREES BELOW NORMAL ON SATURDAY...AND ONLY SLIGHTLY WARMER ON
SUNDAY. THIS COLD COMBINED WITH PLENTY OF AVAILABLE MOISTURE WILL
MEAN GRADUALLY FALLING SNOW LEVELS TONIGHT INTO TOMORROW. AFTER
COORDINATION WITH SURROUNDING OFFICES AND CONSIDERING IMPACTS
ASSOCIATED WITH THE HOLIDAY WEEKEND HAVE MADE THE DECISION TO
HOIST A WINTER WEATHER ADVISORY FOR 1 TO 4 INCHES OF SNOW FROM
NOON SATURDAY THROUGH 9 AM SUNDAY FOR CENTRAL MOUNTAIN ZONES ABOVE
7000 FT. THOSE PLANNING OUTDOOR ACTIVITIES WILL NEED TO DRESS FOR
THE COLD AND WET CONDITIONS. CANNOT RULE OUT SOME PATCHY SLUSH ON
ROADWAYS AT PASS LEVEL AT TIMES...ESPECIALLY OVERNIGHT. OUTSIDE OF
THE CENTRAL MOUNTAINS EXPECT SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS FROM THIS AFTERNOON THROUGH TOMORROW
EVENING...PARTICULARLY ACROSS THE EASTERN HIGHLANDS. WILL ALSO BE
POTENTIAL FOR SOME SNOW ACROSS THE HIGHER ELEVATIONS OF THE
EASTERN HIGHLANDS LATE SATURDAY NIGHT INTO SUNDAY MORNING...BUT
WITH MORE LIMITED MOISTURE SNOW AMOUNTS WILL LIKELY BE LIMITED TO
LESS THAN ONE INCH. A DRY SLOT WILL PUNCH ACROSS THE SNAKE RIVER
PLAIN LATE TONIGHT...ENDING PRECIPITATION CHANCES THERE BY
SATURDAY MORNING. PRECIPITATION SHOULD END ACROSS THE EASTERN
HIGHLANDS SATURDAY NIGHT AND ACROSS THE CENTRAL MOUNTAINS SUNDAY
MORNING AS DRYER AIR RAPIDLY RACES INTO THE AREA FROM SOUTH TO
NORTH. EXPECT DRY BUT BREEZY CONDITIONS ON SUNDAY...PARTICULARLY
ACROSS THE SNAKE RIVER PLAIN AND EASTERN HIGHLANDS. AD

LONG TERM...RATHER BENIGN CONDITIONS EXPECTED FOR THE LONG TERM
AS MAINLY DRY ZONAL FLOW SETS UP ACROSS THE REGION. A WEAK WAVE
EMBEDDED IN THE FLOW WILL PASS THROUGH MONTANA ON MONDAY...WHICH
WILL RESULT IN INCREASED CLOUD COVER ACROSS THE NORTH...ALONG WITH
A SLIGHT CHANCE FOR AN ISOLATED SHOWER. A SIMILAR DISTURBANCE MAY
RIPPLE THROUGH THE FLOW AROUND MIDWEEK AS WELL...WITH AGAIN
INCREASED SHOWER POTENTIAL ACROSS THE NORTH. GUIDANCE IN
REASONABLY GOOD AGREEMENT IN ITS DEPICTION OF INDICATING A BUILDING
RIDGE ACROSS THE WEST COAST BY LATE WEEK... LENDING INCREASED
CONFIDENCE IN CONTINUED MODERATION OF SURFACE TEMPERATURES TO
ABOVE NORMAL FROM MIDWEEK THROUGH THE END OF NEXT WEEK. AD

AVIATION...AN UPPER LEVEL LOW SYSTEM CURRENTLY OVER WASHINGTON AND
OREGON IS STARTING TO BRING BREEZY WINDS ACROSS THE SNAKE RIVER
PLAIN THIS AFTERNOON. ADDITIONALLY...LOOK FOR VICINITY THUNDERSTORMS
FOR KSUN...KIDA AND TO AN LESSER EXTENT FOR KPIH LATER THIS
AFTERNOON THROUGH EARLY EVENING. EXPECT VICINITY SHOWERS OVERNIGHT
FOR KPIH...KIDA AND KSUN. ALSO...LOOK FOR A CHANCE OF SHOWERS AND
THUNDERSTORMS AS WELL AS MODERATE TO STRONG WINDS AGAIN ON SATURDAY
AFTERNOON. WYATT

FIRE WEATHER...RED FLAG WARNING IN EFFECT FOR GUSTY WINDS AND LOW
HUMIDITY FOR ZONE 427 AS WELL AS 413 BELOW 5000 FEET FROM 1 TO 10
PM.  EXPECT STRONG SOUTHERLY WINDS AHEAD OF THE COLD FRONT IN THESE
ZONES WITH GUSTS OF 25 TO 35 MPH EXPECTED THIS AFTERNOON INTO EARLY
EVENING WITH MINIMUM HUMIDITY AROUND 13 TO 20 PERCENT. LOOK FOR
WINDY CONDITIONS IN THOSE ZONES SATURDAY AS WELL BEHIND THE COLD
FRONT. HOWEVER... HUMIDITY WILL BE SUBSTANTIALLY HIGHER WITH MUCH
COOLER TEMPERATURES. EXPECT WETTING RAINS TODAY AND SATURDAY MAINLY
IN OUR NORTHERN ZONES 475...476 AND 422 AS THE UPPER LOW PUSHES EAST
THROUGH NORTHERN IDAHO.  ALSO...LOOK FOR 1 TO 4 INCHES OF SNOW ABOVE
7000 FEET MAINLY IN THE CENTRAL MOUNTAINS. WYATT

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 10 PM MDT THIS EVENING FOR IDZ413-427.

WINTER WEATHER ADVISORY FROM NOON SATURDAY TO 9 AM MDT SUNDAY
FOR IDZ018-032.

&&

$$


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