Area Forecast Discussion
Issued by NWS Pocatello, ID

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000
FXUS65 KPIH 221945
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
145 PM MDT WED OCT 22 2014

.SHORT TERM...A WEAK HIGH PRESSURE RIDGE WILL BE MOVING ACROSS
SOUTHEAST IDAHO TONIGHT. NORTHEASTERLY SURFACE WINDS EXPECTED IN THE
SNAKE PLAIN...HOWEVER MIDDLE AND HIGH CLOUDS ARE ALREADY SPREADING
IN FROM THE WEST. THIS MAKES FOR TRICKY LOW TEMPERATURES TONIGHT.
FAVORED THE COOLER TEMPERATURES IN THE UPPER PLAIN, SOME WARMING
IN THE SOUTH CENTRAL HIGHLANDS. ALONG THE I-86 CORRIDOR...WARMED
TEMPERATURES A LITTLE OVER WEDNESDAY MORNING BUT THE NORTHEASTERLY
WINDS COULD MAKE THEM GO EITHER WAY. THURSDAY AND FRIDAY...AS MODELS
SUGGESTED YESTERDAY...LOW PRESSURE TROUGH NEAR 135-140W DIGS
SOUTHWARD WITH THE DOWN STREAM MOISTURE PLUME SPREADING ACROSS THE
NORTH HALF OF THE FORECAST AREA, WHICH BOWS NORTHWARD BY FRIDAY
NIGHT UNDER AN AMPLIFYING HIGH PRESSURE RIDGE. SNOW LEVELS ABOUT
8000 FEET FRIDAY RISING TO NEAR 10000 FEET BY THURSDAY EVENING. VERY
LIMITED ACCUMULATION IN THE HIGHER ELEVATIONS AROUND 1 TO 4 INCHES.
CONTINUE TO WATCH MOISTURE FROM FORMER TROPICAL CYCLONE ANA WEST OF
HAWAII. LATEST GFS MODEL DRAWS SOME OF THIS MOISTURE INTO THE
EASTERN PACIFIC TROUGH...BUT WITH THE RIDGE AMPLIFYING OVER
IDAHO...FRIDAY AND SATURDAY THE MAIN MOISTURE ENDS UP MOVING INTO
OREGON...WASHINGTON AND THE IDAHO PAN HANDLE. WE STILL HAVE TO WAIT
UNTIL THE TROUGH IN THE EASTERN PACIFIC TRIES TO MOVE INLAND A DAY
OR TWO LATER. RS

.LONG TERM...SAT NIGHT THROUGH NEXT WED NIGHT. UPPER LEVEL TROUGH
STILL EXPECTED TO BRING RAIN AND SNOW WITH SNOW STAYING ABOVE 6000
FEET OR SO. GUIDANCE TRENDS HAVE BEEN TO SLOW ITS EXIT...SO HAVE
BOOSTED POPS FOR SUN NIGHT AND MON. THERE ARE STRONG MODEL
DIFFERENCES BEYOND SUN NIGHT WITH THE WETTER GFS SCENARIO AND A
DRIER ECMWF. THIS HAS BEEN HAPPENING FOR THE SEVERAL DAYS...BUT THE
GFS HAS BEEN MORE RELIABLE. THE ECMWF IS TRENDING WETTER WITH THE
UPPER LEVEL RIDGE NOW GONE DURING THE MON-TUE TIMEFRAME. TENDED TO
BELIEVE THE GFS MORE...BUT NCEP HAS CONTINUED TO RECOMMEND A BLEND
OF THE TWO MODELS. THE GFS IS BRINGING UP MORE MOISTURE FROM THE
TROPICAL SYSTEM ANA THAN THE ECMWF...WHICH MAKES TUE-WED A VERY WET
PERIOD ON THE GFS FOR SOUTHERN IDAHO. THE FASCINATING THING IS THAT
THE MORE MILD TROPICAL AIR OF THE GFS KEEPS TEMPERATURES MILD IN
SPITE OF THE CLOUD COVER...WHILE THE DRIER ECMWF KEEPS TEMPERATURES
MAINLY IN THE SAME RANGE DUE TO ITS CLEAR SKIES. THE ONLY STRONG
DISCREPANCIES OCCUR ON MONDAY IN THE SNAKE RIVER PLAIN.  AN
AVERAGE OF THE TWO MOS GUIDANCE PRODUCTS GIVES A MORE REASONABLE
MAXIMUM TEMPERATURE FORECAST FOR MON...AT LEAST FOR NOW. MESSICK

&&

.AVIATION...UPPER LEVEL HIGH ALLOWING MID- AND HIGH LEVEL CLOUDINESS
TO MOVE INTO SOUTHERN IDAHO...COMMONLY CALLED A DIRTY RIDGE
SITUATION. MID-LEVEL CIGS SHOULD DEVELOP LATE TONIGHT AND CONTINUE
MOST OF THE DAY ON THU. WIND SHOULD CONTINUE LIGHT AND NO VSBY
RESTRICTIONS. MESSICK

&&

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

&&

$$







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