Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 232332
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
432 PM MST FRI JAN 23 2015

.UPDATE...

SATELLITE SHOWS WIDESPREAD LOW STRATUS ALREADY OVER THE MAGIC
VALLEY AS OF 23Z. UPDATED FORECAST FOR CLOUD COVER THIS EVENING AS
A RESULT.

VALLE

&&

.PREV DISCUSSION... /ISSUED 153 PM MST FRI JAN 23 2015/

SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT. UPPER RIDGE REMAINS IN
PLACE WITH NOSE EDGING INTO EASTERN IDAHO THIS AFTERNOON PER WV
SAT IMAGERY. MOISTURE SPILLING OVER THE TOP OF THE RIDGE
ASSOCIATED WITH WEAK SHORTWAVES APPROACHING THE COAST. FIRST
SHORTWAVE DROPS THROUGH PANHANDLE LATE TONIGHT AND SLIDES ALONG
DIVIDE DURING THE DAY SATURDAY. LOW LEVEL INVERSIONS STILL IN
PLACE SO HAVE MAINTAINED PATCHY FZFG IN SNAKE PLAIN AND AREAS
ALONG THE WYOMING BORDER OVERNIGHT. NAM REMAINS WETTER MODEL RUN
TODAY AND HAVE KEPT POPS IN LOW CHANCE CATEGORY IN PORTIONS OF
CENTRAL MTNS AND IN YELLOWSTONE REGION THROUGH SATURDAY WHILE
SPREADING WEAK POPS FURTHER SOUTH ALONG WYOMING BORDER. QPF LIGHT
DESPITE WETTER SIGNAL SO EXPECT SNOW AMOUNTS TO REMAIN LIGHT EVEN
AT HIGHER ELEVATIONS. MOISTURE LINGERS INTO EARLY SUNDAY THUS
MAINTAINED VERY WEAK POPS WITH LITTLE TO NO MENTION. INVERSION
CONDITIONS REBUILD...IF THEY EVER FULLY ERODE UNDER WEAK DYNAMIC
MIXING. CONDITIONS COULD BE FAVORABLE FOR RETURN OF STRATUS/FOG
EARLY IN THE WEEK. DMH

LONG TERM...MON THROUGH NEXT FRI NIGHT. WETTER GFS IS SLIGHTLY
DIFFERENT IN TIMING WITH PRECIPITATION FROM A LOW MOVING UP FROM THE
SOUTH REACHING THE FORECAST AREA BY MON NIGHT. ECMWF IS MUCH SLOWER
IN THE ARRIVAL OF THIS FEATURE...HOLDING BACK SIGNIFICANT
PRECIPITATION UNTIL TUE. HOWEVER...THEY BOTH ARE SIMILAR ON TUE
NIGHT...THEN THE GFS TURNS DRIER WITH A QUICKER EXIT AS IT BRINGS
BACK THE NORTHERN BRANCH AND A COLDER SCENARIO FOR THE LAST TWO TO
THREE DAYS OF THE PERIOD. THE LOCAL OFFICE HAS HAD TROUBLE RECEIVING
THE ECMWF AND SO DONT KNOW ITS TRACK RECORD FOR THE LAST FEW DAYS.
IT MUST BE SAID THAT THE SNOW LEVEL IS EXTRAORDINARILY HIGH...OVER
10000 FT ELEVATION STILL. HAVE TAKEN THE GFS SOLUTION FOR THIS AND
MODIFIED IT HIGHER. THE LAST 24 HOURS ARE VERY SIMILAR AMONG THE
SOLUTIONS AND THUS HAVE MADE THE FORECAST MUCH DRIER UNDER THE
NORTHWEST FLOW BOTH ECMWF AND GFS HAS BY THIS POINT. MESSICK

AVIATION...STRATUS AND FOG CONTINUE TO BE THE MAIN PROBLEM. MOS
GUIDANCE DOES NOT SEEM TO BE OF MUCH HELP WITH KPIH AND KIDA AS THEY
ARE ALREADY NOT VERIFYING. LOOKING AT NAM BOUNDARY LAYER HUMIDITY
AND VERTICAL VELOCITIES IN THE LAYER...HAVE PUT IN FOG AND STRATUS
FOR THOSE TWO LOCATIONS DURING THE OVERNIGHT AND MORNING
HOURS...WITH WORST CONDITIONS AROUND/AFTER SUNRISE. KBYI HISTORY
INDICATES LITTLE CHANCE OF A BREAKOUT WITH IFR RETURNING DURING THE
EVENING HOURS. NORTHWEST SURFACE FLOW CONTINUING EVEN INTO THE
AFTERNOON SHOULD KEEP THE FOG-MONSTER AWAY FROM KSUN.
SNOW/PRECIPITATION BEGINS TO MOVE INTO THE CENTRAL IDAHO MOUNTAINS
ABOUT 24/15Z OR SO. HAVE INCLUDED VCSH AS THE TROUGH DOES LITTLE TO
CHANGE THE NORTHWEST DOWNSLOPE OVER THE WOOD RIVER VALLEY...AND AT
THIS POINT DO NOT EXPECT SIGNIFICANT IMPACT FOR KSUN--IN THE MORNING
AT LEAST. COULD BE DIFFERENT DURING THE AFTERNOON. MESSICK

&&

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

$$






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