Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 231959
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
159 PM MDT TUE SEP 23 2014

.SHORT TERM...TONIGHT THROUGH THURSDAY. A SIGNIFICANT LOW PRESSURE
TROUGH WAS DEVELOPING OFF THE NW COAST EARLY THIS AFTERNOON.
NUMERICAL WEATHER MODELS SHOW THE TROUGH AMPLIFYING WEDNESDAY WHICH
WILL PUMP A RIDGE OF HIGH PRESSURE UP ACROSS THE GREAT BASIN/ROCKY
MOUNTAINS RESULTING IN MUCH WARMER CONDITIONS. AFTERNOON HIGHS
WEDNESDAY AND THURSDAY ARE EXPECTED TO APPROACH RECORD LEVELS FOR
THIS TIME OF YEAR. HUSTON

.LONG TERM...FRIDAY THROUGH NEXT TUESDAY. THE TROUGH POSITIONED
ALONG THE NW COAST WILL PROGRESS INLAND FRIDAY WITH PRELIMINARY
SCATTERED SHOWER ACTIVITY SPREADING INTO MAINLY THE CNTRL MOUNTAINS
THURSDAY NIGHT/FRIDAY. THE 12Z GFS/GEM AND LAST NIGHTS 00Z ECMWF ALL
SHOWED A CLOSED LOW CIRCULATION DEVELOPING OVER NRN CALIFORNIA BY
SATURDAY MORNING WITH THE GFS/ECMWF DIGGING IT SOUTH TOWARD
SACRAMENTO WHILE THE GEM LIFTED IT NORTH INTO THE SRN CASCADE RANGE.
DESPITE THE VARYING TRAJECTORIES...ALL THE MODELS SHOWED A FAIRLY
INTENSE PRECIPITATION BAND DEVELOPING OVER SRN IDAHO PRIMARILY WEST
OF RAFT RIVER SATURDAY AFTERNOON/NIGHT. BY SUNDAY MORNING...THE
UPPER LOW IS EXPECTED TO SPREAD NORTH OF WINNEMUCCA WITH THE
ATTENDING PRECIPITATION BAND SHIFTING INTO SE IDAHO. WIDESPREAD...
BUT DECREASING PRECIPITATION WAS ANTICIPATED BY SUNDAY AFTERNOON AS
THE LOW SHIFTED FURTHER NORTH WITH CONSIDERABLE MODEL SPREAD.
THUS...HAVE TARGETED SATURDAY NIGHT/SUNDAY MORNING WITH THE HIGHEST
PRECIPITATION POTENTIAL AND IF THE MODELS MAINTAIN THIS TIMING...I
WOULD EXPECT THE FORECAST PROBABILITIES TO RISE AS THE EVENT DRAWS
NEAR AND FORECAST CERTAINTY INCREASES. BY MONDAY...THE LOW SHOULD BE
EJECTING NE ACROSS MONTANA WITH A MOIST UPSLOPE NW FLOW CONTINUING
ALONG THE MONTANA/WYOMING DIVIDE REGIONS INTO TUESDAY. HUSTON
&&

.AVIATION...WILL HAVE VFR CONDITIONS THROUGH THURSDAY. EXPECT AN
INCREASE IN WINDS THURSDAY AFTERNOON AT BYI...PIH AND IDA TO 10 TO
20 KNOTS. GK
&&

.FIRE WEATHER...STRONG SOUTHERLY FLOW ALOFT WILL CONTINUE WARM AND
MAINLY DRY WEATHER THROUGH THURSDAY. EXPECT SOUTHERLY WIND GUSTS IN
THE 20 TO 30 MPH RANGE ON THURSDAY AFTERNOON. THE PATTERN WILL BEGIN
TO CHANGE FRIDAY AS THE THREAT FOR SHOWERS INCREASES WITH VERY WET
AND COOL CONDITIONS EXPECTED OVER THE WEEKEND. GK
&&

.PIH WATCHES/WARNINGS/ADVISORIES...NONE.
&&

$$










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