Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 230307
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
907 PM MDT FRI APR 22 2016

.UPDATE...DEEP UPPER LOW CUTTING THROUGH THE GREAT BASIN THIS
EVENING PER SATELLITE IMAGERY. RADAR SHOWING BROAD AREAS OF LIGHT
SHOWERS PUSHING THROUGH THE CENTRAL MOUNTAINS WITH ANOTHER BATCH
WORKING INTO THE SOUTHERN HIGHLANDS ALONG THE UTAH BORDER. THERE
HAVE BEEN A FEW LIGHTNING STRIKES MAINLY JUST WEST OF THE FORECAST
AREA BUT THE STRONGER CONVECTIVE ACTIVITY APPEARS TO BE WEAKENING
WITH LOSS OF DAYTIME HEATING. HAVE NUDGED POPS UP SLIGHTLY FOR THE
REMAINDER OF THE EVENING MAINLY ACROSS THE MAGIC VALLEY SINCE
RADAR SHOWS WEAK RETURNS IN THAT REGION. HAVE DOUBTS THAT MUCH IF
ANY PRECIPITATION IS REACHING THE GROUND GIVEN THE STEEP SURFACE
DEWPOINT DEPRESSIONS BUT SPRINKLES ARE NOT OUT OF THE QUESTION.
SURFACE TROUGH STRETCHES ACROSS THE REGION WITH STRONG WIND SHIFT
BETWEEN POCATELLO AND RAFT RIVER AREA. EXPECT SFC TROUGH AND COLD
FRONT TO SHIFT EAST WITH PASSAGE THROUGH POCATELLO ROUGHLY 09Z.
WIND ADVISORY STILL IN PLACE WITH STRONG SURFACE GRADIENT DURING
THE DAY SATURDAY. OVERALL FORECAST IN GOOD SHAPE SO ONLY A FEW
MINOR TWEAKS. DMH

&&

.PREV DISCUSSION... /ISSUED 202 PM MDT FRI APR 22 2016/

SHORT TERM...THE FIRST OF A SERIES OF LOW PRESSURE DISTURBANCES
WILL BRING SHOWERS AND LOWERING SNOW LEVELS TO SOUTHEAST IDAHO
TONIGHT AND SATURDAY. SHOWERS WITH ISOLATED THUNDERSTORMS ARE
DEVELOPING ON THE LEADING EDGE OF THE DISTURBANCE MOVING INLAND
ALONG THE CALIFORNIA AND OREGON BORDER THIS AFTERNOON. A FEW
LIGHTING STRIKES HAVE BEEN NOTED NEAR THE OREGON AND IDAHO BORDER
THIS AFTERNOON. MOST OF THE SHOWERS ARE MOVING SOUTH TO NORTH ON
THE LEADING EDGE WHICH SHOULD REACH THE SUN VALLEY AND BURLEY
LATER THIS EVENING. PROGRESSION INTO THE UPPER SNAKE PLAIN WILL
TAKE UNTIL AROUND SATURDAY MORNING. AS THE LOW PASSES ON
SATURDAY...SHOWERS BECOME MORE NUMEROUS AND SNOW LEVELS WILL
BEGIN TO LOWER...REACHING ABOUT 7000 FEET ELEVATION BY SUNDAY
MORNING. FROM 1 TO 5 INCHES OF SNOW IS POSSIBLE IN THE CENTRAL
MOUNTAINS AND EASTERN HIGHLANDS WITH SOME ACCUMULATION EXPECTED ON
THE PASSES. LOWS TONIGHT WILL REMAIN MOSTLY ABOVE FREEZING AND
THUS THERE WILL BE A GOOD DEAL OF MELTING EVEN IN THE PASSES. HIGH
TEMPERATURES FALL ABOUT 20 DEGREES SATURDAY. A WIND ADVISORY HAS
BEEN ISSUED FOR AREAS OF SOUTHEAST IDAHO FROM BURLEY TO POCATELLO
AND ALONG INTERSTATE 84 THROUGH SUBLETT. SATURDAY NIGHT THERE WILL
BE A SHORT BREAK BEFORE THE NEXT DISTURBANCE BEGINS TO AFFECT THIS
AREA SUNDAY AFTERNOON AND CONTINUING THROUGH MONDAY NIGHT OR
TUESDAY. RS

LONG TERM...MONDAY THROUGH FRIDAY NIGHT. GAINING CONFIDENCE IN
EARLY WEEK FORECAST AS ECMWF/GFS COMING INTO AGREEMENT WITH TRACK OF
UPPER LOW OVER THE GREAT BASIN MONDAY NIGHT INTO TUESDAY. SEEING
ENOUGH INSTABILITY MONDAY AFTERNOON TO INCLUDE THUNDER MENTION OVER
THE EASTERN HIGHLANDS AND CENTRAL MOUNTAINS. TEMPS ALSO TAKING A
DIVE AS COOLER AIR LINGERS OVER MUCH OF THE REGION. HIGHS MONDAY
THROUGH WEDNESDAY WILL STRUGGLE TO REACH 60 DEGREES ACROSS SOUTHEAST
IDAHO. POPS DROP OFF SOMEWHAT TUESDAY NIGHT AND WEDNESDAY THANKS TO
A TRANSIENT RIDGE...BUT WILL SEE A RETURN OF ACTIVE WEATHER
WEDNESDAY NIGHT AS ANOTHER UPPER LOW SINKS INTO THE DESERT
SOUTHWEST. ECMWF TRACKS THE LOW A BIT FURTHER SOUTH THAN THE GFS.
BOTH ARE INDICATING ACTIVE WEATHER HEADING INTO NEXT
WEEKEND...HOWEVER TEMPERATURES SHOULD WARM BACK INTO THE 60
THURSDAY. SNOW LEVELS WILL BE AT THEIR LOWEST PRIOR TO
WEDNESDAY...BUT SHOULD REMAIN ABOVE THE VALLEY FLOOR.  HINSBERGER

AVIATION...STRONG SOUTHERLY FLOW IN THE LOW AND MID LEVELS KEEPING
TEMPS WARM. INCREASING MID AND HIGH CLOUDS EXPECTED LATER TONIGHT IN
ADVANCE OF APPROACHING COLD FRONT WHICH IS EXPECTED TO PASS KPIH
AROUND 06Z. BEST CHANCE FOR THUNDER TODAY WILL BE IN KBYI AND KSUN.
MODELS OTHERWISE HOLDING OFF ON PRECIP UNTIL A FEW HOURS AFTER
FRONTAL PASSAGE TONIGHT WITH CEILINGS DROPPING TO MVFR/IFR AT ALL
SITES BETWEEN 09Z AND 14Z. CONCERN FOR LOW LEVEL WIND SHEAR AGAIN
TONIGHT IN THE PRE-FRONTAL AIR AS LOW-LEVEL WINDS INCREASE...BUT
SURFACE WINDS MAY STAY ELEVATED THROUGH THE NIGHT TO MITIGATE THE
SHEAR.  HINSBERGER

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM NOON TO 10 PM MDT SATURDAY FOR IDZ017-021-022.

&&

$$


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