Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 160406
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
906 PM MST SAT NOV 15 2014

.UPDATE...COLD NORTH FLOW IN PLACE OVER EAST IDAHO. FOG/IR SHOWS
STRATUS THROUGH MAGIC VALLEY AND INTO THE SOUTHERN HIGHLANDS. AREA
WEB CAMS SHOWING A FEW FLURRIES EMBEDDED IN THE STRATUS...A
PRODUCT OF FAVORABLE TEMP PROFILE BUT NO FORCING DYNAMICS.
OTHERWISE CLEAR SKIES...LIGHT WINDS...AND FRESH SNOW COVER
ALLOWING TEMPS TO PLUMMET TONIGHT. MODEL SOUNDINGS SHOW THAT
STRATUS IS FAVORED OVERNIGHT. HAVE MADE A FEW TWEAKS TO OVERNIGHT
TEMPS AND NUDGED SKY COVER UP AT LOWER ELEVATIONS IN PREVIOUSLY
MENTIONED AREAS FOR STRATUS. OTHERWISE FORECAST IN GOOD SHAPE. NO
OTHER UPDATES PLANNED THIS EVENING. DMH


&&

.PREV DISCUSSION... /ISSUED 1255 PM MST SAT NOV 15 2014/

SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT. EXPECT PATCHY FOG AND
LOW CLOUDS LATE TONIGHT AND SUNDAY MORNING IN THE LOWER SNAKE
PLAIN AS CLEAR SKIES...LIGHT WINDS AND SUBLIMATION OF SNOW COVER
PROVIDE OPTIMAL CONDITIONS FOR FOG AND STRATUS DEVELOPMENT.
SOUTHEAST IDAHO WILL REMAIN CHILLY AND DRY THROUGH THE PERIOD AS A
STATIONARY HIGH AMPLITUDE RIDGE SETS UP ALONG THE WEST COAST. THE
UPPER LEVEL FLOW WILL REMAIN OUT OF THE NORTH AND CONTINUE TO
TRANSPORT COLD AIR SOUTHWARD. THE UPPER RIDGE SLOWLY SHIFTS INLAND
AND DAYTIME TEMPERATURES WILL MODERATE WITH GRADUAL WARMING AND
APPROACH CLIMATE NORMS ON TUESDAY. NIGHTTIME TEMPERATURES WILL
REMAIN WELL BELOW NORMAL THROUGH THE PERIOD WITH OVERNIGHT LOWS IN
THE SINGLE DIGITS IN THE SNAKE PLAIN AND AS LOW AS -25 DEGREES IN
HIGH ELEVATION BASINS.

LONG TERM...WED THROUGH NEXT SAT NIGHT. 500MB LONGWAVE PATTERN
TRANSITIONS FROM A HIGH AMPLITUDE RIDGE ON THE PACIFIC COAST QUICKLY
DE-AMPLIFYING WITH A MOVE INTO THE INTERMOUNTAIN WEST BY FRI
AFTERNOON. IT IS VERY NEARLY ZONAL FLOW BY SAT. THIS MEANS THAT THE
PERIOD OF DRY AND COLD WILL CHANGE...BUT THERE ARE LARGE DIFFERENCES
IN GUIDANCE SOLUTIONS FOR THE TIMING OF SHORTWAVE ARRIVALS AND
DEPARTURES IN THE NORTHWESTERN UNITED STATES. FOR INSTANCE...THE
ECMWF HAS A SHORTWAVE PUSHING THROUGH WED NIGHT/THU...WHILE THE GFS
HAS THE SHORTWAVE ARRIVING FROM FARTHER SOUTH...ON THU...AND
LINGERING THROUGH FRI. BOTH PRODUCT SUITES DO CURRENTLY AGREE ON A
SIGNIFICANT SHORTWAVE ARRIVING LATE SAT AFTERNOON AND PUSHING
THROUGH NEXT SAT NIGHT. THE OTHER SURE THING IS THAT THE STRONG
NORTHERLY AIR FLOW SHOULD END...AND TEMPERATURES WILL BE WARMER AS A
RESULT. THUS THIS IS A LOW-CONFIDENCE FORECAST RIGHT NOW...SUBJECT
TO POTENTIALLY LARGE CHANGES FROM ONE DAY TO THE NEXT. MESSICK

AVIATION...HIGH PRESSURE IS TAKING OVER THE WEATHER SITUATION.
CLEARING SKIES ALOFT WITH LIGHT WIND OPENS UP THE OPPORTUNITY FOR
STRATUS AND FOG LATE TONIGHT AND EARLY SUN MORNING. GFS IS ITS USUAL
OPTIMISTIC SELF...WHILE THE NAM HAS BEEN CONSISTENTLY FORECASTING A
HIGH MOISTURE CONTENT BOUNDARY LAYER IN THE SNAKE RIVER
PLAIN...MAINLY IN THE SOUTHERN END. THUS HAVE PUT IN THE STRATUS
FORECASTED BY THE NAM GUIDANCE...WHICH SHUTS DOWN KBYI AND MAKES
KPIH RATHER QUESTIONABLE. MEANWHILE...THE KIDA AND KSUN AIRDROMES
ARE NOT EXPECTED TO HAVE PROBLEMS TONIGHT OR SUN MORNING. MESSICK

&&

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

$$








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