Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 051949
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
150 PM MDT SUN JUL 5 2015

.DISCUSSION...THE LATEST SATELLITE IMAGERY WAS SHOWING A VIGOROUS
LOW PRESSURE TROUGH SHEARING EAST ALONG THE CANADIAN BORDER WHILE A
SUB-TROPICAL DISTURBANCE WITH ACCOMPANYING CLOUDS AND SHOWERS
ROTATED NNE ACROSS SE IDAHO. VISIBLE SATELLITE IMAGERY WAS SHOWING A
BROAD AREA OF RELATIVELY CLEAR SKIES ACROSS NRN NEVADA/UTAH. SUSPECT
THAT MAXIMUM SOLAR INSOLATION COUPLED WITH THE RELATIVELY MOIST
BOUNDARY LAYER ALONG THE NEVADA/UTAH BORDER WILL BE A FAVORED AREA
FOR CONVECTIVE DEVELOPMENT LATER THIS AFTERNOON. NUMERICAL MODELS
CONTINUE TO HIGHLIGHT POTENTIAL DEVELOPMENT ALONG A LINE FROM ARCO
TO MONIDA PASS AS WELL...LIKELY OWING TO THE PASSING DYNAMICS
ASSOCIATED WITH THE CANADIAN TROUGH...BUT AT THIS POINT I AM
WONDERING IF THE CLOUD COVER WILL INHIBIT SURFACE HEATING AND
BUOYANCY. A BACK-DOOR FRONT SPILLS OVER THE DIVIDE LATER TONIGHT AND
THE MODELS ARE RESPONDING WITH ONGOING CONVECTION (MUCH MORE SO THAN
IN PREVIOUS RUNS) AND THUS HAVE BUMPED THE SHOWER POTENTIAL UP SOME
FOR THIS POSSIBILITY. BOTH THE GFS AND NAM ARE SHOWING A SECONDARY
FEATURE SHEARING EAST ACROSS SRN IDAHO MONDAY...INTERACTING WITH
RESIDUAL LOW LEVEL MOISTURE AND THE REMNANTS OF THE BACK DOOR FRONT
TO PRODUCE A FAIRLY ACTIVE DAY OF CONVECTION. HAVE NUDGED THE
FORECAST UP SLIGHTLY AND SUSPECT IF THIS SCENARIO DOES PAN OUT THAT
WE MAY HAVE TO GO A LITTLE FURTHER IN THIS REGARD.

THE REMAINDER OF THE FORECAST LOOKED GOOD AS WE CONTINUE TO AWAIT
SOMETHING MORE DEFINITIVE WITH REGARDS TO THE TIMING AND TRACK OF
THE INCOMING SUB-TROPICAL LOW CURRENTLY PARKED OFF THE CNTRL
CALIFORNIA COAST. TODAYS RUNS HAVE OFFERED UP YET ANOTHER DAYS DELAY
IN THE PASSING OF THE UPPER LOW (NOW WAITING UNTIL FRIDAY) AND A
TRACK THAT IS INITIALLY FURTHER SOUTH. HOWEVER...THERE DOES APPEAR
TO BE BETTER AGREEMENT AMONG THE MODELS...ALBEIT FOR THIS RUN. THE
RUN TO RUN AGREEMENT IS STILL POOR WHICH ADDS TO THE UNCERTAINTY.
HUSTON
&&

.AVIATION...SHOWERS DEVELOPED IN NORTHERN UTAH THIS MORNING AND HAVE
BEEN SLOWLY PUSHING NORTHWARD TODAY. CONTINUED HEATING AND ADDED
INSTABILITY FROM AN ASSOCIATED WEAK FRONT SHOULD GENERATED AT LEAST
SOME ISOLATED -TSRA DURING THE AFTERNOON AND EVENING HOURS...TS
SHOULD END BETWEEN 06/03Z AND 06/06Z. -SHRA WILL CONTINUE...BUT WILL
BE MORE SPOTTY AND FARTHER NORTH...MAINLY AFFECTING KSUN UNTIL MON
MORNING. WIND WILL BE ELEVATED DURING THE AFTERNOON...BUT IS NOT
DEVELOPING AS STRONGLY AS GUIDANCE INDICATED...THOUGH EXPECTED TURN
TO SOUTHERLY WIND HAS OCCURRED. NO IMPACT TO VSBY OR CIG EXPECTED
WITH THE -TSRA DEVELOPMENT...JUST NORMAL WIND
SHEAR...LIGHTNING...AND HAIL HAZARDS ASSOCIATED WITH STORM CELLS.
MESSICK
&&

.FIRE WEATHER....SCATTERED THUNDERSTORMS FOR THE NEXT TWO
AFTERNOONS/EVENINGS ARE EXPECTED AS UNSTABLE AIR FROM THE SOUTH HAS
PUSHED INTO EASTERN AND CENTRAL IDAHO. THE CLOUDS WILL DECREASE
TEMPERATURE AND ALSO PROVIDE A LITTLE RELIEF IN THE AFTERNOON
HUMIDITY. WARMING AND DRYING RETURN FOR WED AND THU...BUT THE NEXT
COLD FRONT ARRIVES THU LATE AFTERNOON/EVENING AND BRINGS THE
TEMPERATURES ACTUALLY BELOW NORMAL FOR THE REST OF THE WEEK. THE
HIGH PRESSURE THAT PRODUCED ALL THE HEAT RECORDS DURING LATE JUNE
WILL FULLY BREAK DOWN OVER THE WESTERN STATES AND BE REPLACED BY A
LONGWAVE TROUGH BY THE WEEKEND...SO THE COOLER TEMPERATURES MAY STAY
FOR AN EXTENDED PERIOD...EVEN INTO THE NEXT WEEK. MESSICK
&&

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

$$


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