656
FXUS65 KPIH 051003
AFDPIH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
303 AM MST FRI MAR 5 2021
SHORT TERM
TODAY THROUGH SUNDAY.
EXPECT ANOTHER PLEASANT DAY WITH ABOVE NORMAL TEMPS,
LIGHT WINDS AND NO PRECIPITATION. A WEAK COLD FRONT WILL ARRIVE ON
SUNDAY. QUITE A BIT OF DRY AIR ACROSS THE REGION, SO MOST IF NOT ALL
OF THE PRECIPITATION WITH THIS FRONT WILL OCCUR OVER THE HIGH
COUNTRY. PRECIPITATION WILL BE MAINLY CONFINED TO THE FRONT AS WELL,
SO MOST OF IT WILL OCCUR SATURDAY AFTERNOON. SNOW LEVELS ARE BETWEEN
5500-6500 FT WITH THIS SYSTEM. AMOUNTS LOOK VERY LIGHT WITH AN INCH
OR LESS LIKELY IN AREAS THAT RECEIVE SNOW. POSSIBLY UP TO 2 INCHES
NEAR PASSES SUCH AS GALENA AND BANNER SUMMITS. EXPECT WINDY
CONDITIONS SATURDAY AFTERNOON BUT PERHAPS NOT QUITE TO WIND ADVISORY
LEVELS. WITH THE SNOWPACK RECEDING AND THE DRY WINDY WEATHER
EXPECTED SATURDAY WOULDN'T BE SURPRISED TO SEE A COUPLE BRUSH FIRES
POP UP.
TEMPERATURES COOL OFF A COUPLE DEGREES BEHIND THE FRONT ON SUNDAY
WITH DRY WEATHER ACROSS THE REGION.
13
LONG TERM
MONDAY THROUGH NEXT FRIDAY NIGHT. MONDAY WILL SIGNAL
THE BEGINNING OF A PATTERN CHANGE ACROSS THE REGION AS AN AREA OF
LOW PRESSURE AND ATTENDANT STRONG COLD FRONT APPROACHES FROM THE
WEST. DETERMINISTIC AND ENSEMBLE MODEL GUIDANCE ARE ALL IN
REASONABLY GOOD AGREEMENT, WHICH AIDS FORECASTER CONFIDENCE. FOR THE
DAYLIGHT HOURS ON MONDAY, CENTRAL AND EASTERN IDAHO WILL RESIDE ON
THE WARM SIDE OF THIS SYSTEM, WITH THE COLD FRONT LURKING TO THE
WEST. SNOW SHOWERS WILL DEVELOP ACROSS THE CENTRAL IDAHO MOUNTAINS
MONDAY MORNING, WITH ACTIVITY EXPANDING ACROSS THE MONTANA BORDER
REGION AND ISLAND PARK AREAS BY LATE AFTERNOON/EARLY EVENING. A
NORTHEAST TO SOUTHWEST BAND OF PRECIPITATION FORCED BY UPPER JET/MID-
LEVEL FRONTAL FORCING IS THEN EXPECTED TO DEVELOP ACROSS THE EASTERN
HIGHLANDS OR EASTERN SNAKE PLAIN (THERE REMAINS SOME UNCERTAINTY ON
PLACEMENT) MONDAY EVENING. THIS BAND OF PRECIPITATION IS LIKELY TO
CONTINUE INTO TUESDAY MORNING. SNOW LEVELS ARE INITIALLY EXPECTED TO
BE BETWEEN 6-6,500 FEET WHEN PRECIPITATION BEGINS, BUT A COMBINATION
OF COLD ADVECTION AND DIABATIC COOLING WILL CAUSE SNOW LEVELS TO
FALL TO VALLEY FLOORS AROUND OR SHORTLY AFTER MIDNIGHT. AS THE LONG
TERM PORTION OF THE FORECAST PERIOD PROGRESSES, A BROAD LONGWAVE
TROUGH IS EXPECTED TO TAKE UP RESIDENCE ACROSS THE WESTERN CONUS IN
THE TUESDAY-THURSDAY TIMEFRAME BEFORE IT IS REPLACED WITH BROAD
NORTHWEST FLOW BY LATE WEEK. WITH THE PRESENCE OF THE TROUGH AND
ASSOCIATED COLD AIR ALOFT, ANY DECENT DURATION OF SUNSHINE WILL
STEEPEN LAPSE RATES AND PROMOTE DIURNALLY-ENHANCED SHOWERS,
ESPECIALLY FROM MID AFTERNOON THROUGH EARLY EVENING. OTHERWISE, NO
STRONG FORCING MECHANISMS WILL BE IN PLACE TO FORCE, ORGANIZED
WIDESPREAD PRECIPITATION FROM TUESDAY-THURSDAY, SO ACTIVITY WILL BE
ESPECIALLY DIURNALLY ENHANCED. A WEAK SHORTWAVE IS FORECAST TO BE
SLIDING SOUTHEAST THROUGH THE NORTHWEST FLOW ALOFT BY FRIDAY,
PROMOTING HIGH-ELEVATION SNOW SHOWER ACTIVITY.
AD
AVIATION
VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGH THE
PERIOD AS A RIDGE OF HIGH PRESSURE SLIDES OFF TO THE EAST. AN
APPROACHING TROUGH WILL STRENGTHEN THE PRESSURE GRADIENT TONIGHT INTO
SATURDAY MORNING, AND AS SUCH, MID-UPPER LEVEL FLOW WILL INCREASE.
FORECAST SOUNDINGS INDICATE SSW WINDS INCREASING INTO THE 35-45KT
RANGE BETWEEN 1-2KFT SATURDAY MORNING SHORTLY AFTER SUNRISE -- WITH
A SIMILAR REGIME INDICATED FOR KBYI, KIDA AND KDIJ. THEREFORE, WILL
NEED TO ADD A WIND SHEAR MENTION FOR THESE SITES AT THE TAIL-END OF
THE FORECAST. WINDS WILL INCREASE JUST OFF THE SURFACE AT KSUN AS
WELL, BUT ARE SHOWN TO CLOCK IN JUST BELOW WIND SHEAR THRESHOLDS.
AD
PIH WATCHES/WARNINGS/ADVISORIES
NONE.
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