Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 250918
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
318 AM MDT SAT APR 25 2015

.SHORT TERM...TODAY THROUGH MONDAY AFTERNOON. WE STILL HAVE THE
MAIN LOW CENTERED AROUND SEATTLE AND VANCOUVER THIS MORNING.
ONE WAVE SPINNING AROUND THAT CONTINUES TO SHIFT NORTHEAST THIS
MORNING. BY SUNRISE...LINGERING RAIN AND SNOW WILL BE CONFINED TO
ALONG THE WYOMING BORDER. ANOTHER BATCH WILL EVENTUALLY SHIFT
AWAY FROM THE MACKAY TO ISLAND PARK AREA. SNOW LEVELS ARE DOWN TO
5500-6500FT..SO WE ARE SEEING SNOW DOWN LOW IN THOSE AREAS EARLY
ON. SOME LIGHT ACCUMULATION IS EXPECTED ON GRASSY SURFACES AND IT
APPEARS THAT A FEW SPOTS ARE SEEING SLUSHY/SLICK SPOTS ON THE
ROADS. THEY SHOULD TURN BACK TO WET AFTER THE SUN COMES UP AND
TRAFFIC INCREASES. THE MAIN SYSTEM WILL MOVE EASTWARD SLOWLY AND
SPLITS...WITH A CLOSED LOW FORMING NEAR THE FOUR CORNERS AND THE
NORTHERN BRANCH WEAKENING. MORE CLOUDS ALONG WITH SHOWERS AND
ISOLATED STORMS OVERTAKE EASTERN IDAHO BY AFTERNOON. DON`T BE
SURPRISED IF SOME GUSTY WINDS AND/OR SMALL HAIL OCCUR WITH
STRONGER CELLS...AS WELL AS LOCALLY HEAVIER RAIN OR SNOW. THE
MODELS RAPIDLY DISAGREE FOR TONIGHT/SUNDAY MORNING ON WHERE TO
PLACE THE MAIN BAND OF PRECIPITATION...WHICH ALSO WILL PLAY HAVOC
ON HOW MUCH AIR WORKS IN FROM THE WEST. AS THIS DRY SLOT WORKS UP
THE PLAIN...EXPECT INCREASING WINDS. IRONICALLY...THE MODELS ARE
QUICKLY BACK IN PHASE BY SUNDAY AFTERNOON. THE MAIN AREA OF
PRECIPITATION SHIFTS TO ALONG THE WYOMING BORDER...WITH SOME
LINGERING SHOWERS ACROSS THE CENTRAL MOUNTAINS AND UPPER SNAKE
PLAIN. WE WILL NEED TO MONITOR AS WE MAY SEE A CONVERGENCE BAND
DEVELOP. SNOW LEVELS REBOUND TO 6500-7500FT TOMORROW...BRIEFLY
DROPPING ABOUT 1000FT IN THE MORNING. WE ARE FORECASTING AN
ADDITIONAL 0.10-0.40 INCHES OF WATER. THAT EQUATES TO 1-4 INCHES
IN THE HIGH COUNTRY WITH LIGHT AMOUNTS AT LOWER ELEVATIONS IF AND
WHERE IT MANAGES TO SNOW.

HIGH PRESSURE QUICKLY BEGINS BUILDING ACROSS THE WEST. THAT
RETURNS US TO DRY AND ABOVE NORMAL TEMPERATURES FOR THE FIRST PART
OF THE WORKWEEK. KEYES

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY NIGHT. BOTH GFS AND ECMWF
ARE IN AGREEMENT WITH WARM AND DRY CONDITIONS INTO WED DUE TO A
MAJOR UPPER RIDGE OVER THE WEST. THE RIDGE AXIS MOVES TO THE EAST ON
WED...THE GFS BEING A LITTLE SLOWER. BY WED NIGHT...THE MODELS PART
COMPANY. THE ECMWF DEVELOPS A STRONG ZONAL PATTERN OVER THE PAC
NW...WHILE THE GFS SUGGESTS STRONG SW FLOW AHEAD OF A CLOSED UPPER
LOW OVER THE PAC NW COAST. BOTH MODELS CALL FOR ISOLD SHOWERS/TSTMS
OVER THE CENTRAL MTNS AND EASTERN HIGHLANDS THU THRU SAT. EVENTUALLY
THE MODELS COME TOGETHER SOMEWHAT BY FRI WITH BOTH SHOWING A
POSITIVE TILT UPPER TROF OVER THE WEST. ALTHO NOT CONDUCIVE TO
WIDESPREAD PRECIP...IT WILL RESULT IN COOLER TEMPS BY SATURDAY.
HEDGES

&&

.AVIATION...SCT SHOWERS AND ISOLD TSTMS ARE EXPECTED TO REDEVELOP
THIS AFTN AS A MAJOR UPPER TROF MOVES THRU THE PAC NW. VFR
CONDITIONS ARE EXPECTED THRU THE AFTN...BUT OCNL MVFR AND IFR CIGS
ARE POSSIBLE TONIGHT AS RAIN BECOMES MORE WIDESPREAD. HEDGES

&&

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

$$



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