000
FXUS65 KPIH 272116
AFDPIH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
216 PM MST MON DEC 27 2010
.SHORT TERM...GULF OF ALASKA LOW STILL EXPECTED TO MOVE INTO
SOUTHEAST IDAHO TUESDAY NIGHT AND WEDNESDAY. SUBTLE MODEL
DIFFERENCES SHOWING WITH RESPECT TO UPPER LEVEL CIRCULATION
DEVELOPING EARLIER OVER IDAHO RATHER THAN LATER AND CLOSER TO
UTAH. THE ECM IS SLIGHTLY CLOSER TO THE COAST AND SLOWER WITH THE
TROUGH BY WEDNESDAY MORNING. TOTAL SNOW ACCUMULATION TUESDAY
AFTERNOON THROUGH WEDNESDAY EVENING APPEARS SLIGHTLY LESS. CURRENT
FORECAST WAS ADJUSTED CLOSER TO A FOUR INCH AVERAGE IN THE SNAKE
PLAIN...DOWN FROM ABOUT 5 IN THE PREVIOUS FORECAST. THE MOUNTAINS
AROUND SUN VALLEY AND THE NORTHERN WASATCH WERE TRIMMED BACK 3 TO
5 INCHES AS WELL. UNTIL THE COLD FRONT REACHES THE LOWER SNAKE
PLAIN LATE WEDNESDAY MORNING...SNOW RATIOS SHOULD BE MOSTLY 10 TO
1 IN THE LOWER VALLEYS...15 TO 1 MOUNTAINS. POST FRONTAL COLD AIR
WILL INCREASE RATIOS. NEW SNOW MAY END QUICKER IN THE EASTERN
MAGIC VALLEY AND PORTIONS OF THE LOWER SNAKE PLAIN BEHIND THE
FRONT...A TRADE OFF AS WINDS INCREASE TO 20 TO 30 MPH AND BLOWING
AND DRIFTING BECOMES A THREAT. A CONVERGENCE BOUNDARY DEVELOPS
ROUGHLY BETWEEN IDAHO FALLS AND DUBOIS WEDNESDAY AFTERNOON...THEN
MOVES SOUTH TO INKOM WEDNESDAY EVENING. THAT COULD BRING ANOTHER 2
INCHES OF SNOW CLOSE TO THE EASTERN BENCHES. THE EVENT WILL NOT BE
PAST UNTIL THAT HAPPENS. WINDS DIE DOWN OVER NIGHT AND BY THURSDAY
MORNING THE BLOWING AND DRIFTING SHOULD END. EXPECT SOME AREAS
WILL FALL MORE INTO THE ADVISORY RANGE RATHER THAN WINTER STORM
WARNING AND THE MID SHIFT CAN DO SOME SORTING OUT. RS
.LONG TERM...THURSDAY THROUGH MONDAY. MUCH COLDER PATTERN SETTLES
INTO THE AREA IN THE WAKE OF THE EXITING TROUGH. SOME LINGERING
SNOW SHOWERS WILL HANG AROUND PRIMARILY ACROSS THE SOUTHEAST
HIGHLANDS ON THURSDAY...AND DIMINISH THURSDAY NIGHT. TEMPERATURES
WILL BE STEADY OR SLOWLY FALL THROUGH THE DAY ON THURSDAY...THEN
PLUMMET BELOW ZERO THURSDAY NIGHT AS HIGH PRESSURE AND COLD
NORTHWEST FLOW RESUMES. FRIDAY WILL SEE HIGHS STRUGGLE TO CLIMB INTO
THE SINGLE DIGITS THEN FALL INTO THE TEENS BELOW ZERO FOR MANY
PLACES FRIDAY NIGHT. TEMPERATURES MODERATE SOMEWHAT FOR THE
WEEKEND...HOWEVER MODELS SHOW SIGNIFICANT DISCREPANCIES OVER THE
LOCATION OF AN EVOLVING LOW CIRCULATION AROUND THE SUNDAY AND
MONDAY TIME FRAME. THE ECMWF BRINGS A LOW INTO CALIFORNIA WHILE THE
GFS DROPS A LOW SOUTHWARD ACROSS IDAHO FROM CANADA. GIVEN THE
UNCERTAINTY...HAVE OPTED TO LEAVE THE GOING FORECAST PACKAGE AS IS
FOR THE WEEKEND AND BEYOND.
&&
.AVIATION...VFR CONDITIONS WILL PERSIST THROUGH TONIGHT FOR MUCH OF
THE AREA. SOME ISOLATED SNOW SHOWERS COULD BRIEFLY DROP VIS AND
CEILINGS TO IFR TODAY AND TONIGHT NEAR HIGHER TERRAIN. THE NEXT
POTENT STORM SYSTEM WILL INCREASE MID AND HIGH CLOUDS TONIGHT WITH
SNOW EXPECTED TO MOVE INTO THE WESTERN BORDER BY TUESDAY AFTERNOON
AND BECOMING WIDESPREAD IN EASTERN IDAHO TUESDAY NIGHT. EXPECT
DETERIORATING CONDITIONS TUESDAY WITH IFR AND LIFR LIKELY TUESDAY
NIGHT.
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
AFTERNOON IDZ017-020-021.
WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH WEDNESDAY
AFTERNOON IDZ018-019-022>025-031-032.
&&
$$
