Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 191946
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
146 PM MDT SAT JUL 19 2014

.DISCUSSION...PREDOMINANTLY WESTERLY MID AND UPPER LEVEL FLOW WILL
SHIFT TO THE SOUTHWEST AND OPEN THE DOOR TO MONSOON MOISTURE WHICH
HAS BEEN LURKING OVER THE GREAT BASIN. MOISTURE WILL BEGIN TO
SLIDE NORTH INTO SOUTHERN IDAHO AFTER MIDNIGHT AND WILL SPREAD
NORTH TO A LINE FROM SUN VALLEY TO IDAHO FALLS BY MID DAY. EXPECT
CONVECTION TO FIRE DURING THE EARLY AFTERNOON HOURS...INITIALLY
OVER THE SOUTHERN HIGHLANDS AND SPREAD NORTHWARD THROUGH THE
AFTERNOON AND EVENING HOURS TO COVER MOST OF THE FORECAST AREA.
MODERATE INSTABILITY FOR SUNDAY NIGHT INTO MONDAY MORNING SHOULD
ALLOW SHOWERS AND A FEW THUNDERSTORMS TO PERSIST DURING THE
OVERNIGHT HOURS AS WELL. EXPECT REDEVELOPMENT OF ISOLATED TO
SCATTERED THUNDERSTORMS FOR MONDAY AFTERNOON AND EVENING OVER MOST
OF THE FORECAST AREA AS WELL AS MONSOON MOISTURE AND INSTABILITY
REMAIN IN PLACE. ONE LIMITING FACTOR MAY BE RESIDUAL HIGH LEVEL
CLOUDS FROM EARLIER CONVECTION WHICH COULD CAP INSTABILITY SOMEWHAT.

A LOW PRESSURE SYSTEM APPROACHING THE WA COAST ON TUESDAY TURNS
THE UPPER LEVEL FLOW MORE SOUTHERLY AND DRAWS REMAINING MONSOON
MOISTURE PLUM NORTHWARD. THIS SHIFTS THE AREA OF CONCERN FOR
SHOWERS AND THUNDERSTORMS INTO THE CENTRAL MOUNTAINS FOR TUESDAY
AND WEDNESDAY AFTERNOON AND EVENING. THE UPPER LOW TRACKS INLAND
AND MOVES NORTHEAST INTO ALBERTA ON THURSDAY AND DRAWS MOISTURE
NORTHWARD OUT OF THE FORECAST AREA. EXPECT BREEZY TO WINDY
CONDITIONS FOR THURSDAY AS THE SYSTEM PASSES TO THE NORTH. FLOW
REGIME OVER IDAHO RETURNS TO A DRY WESTERLY FLOW FOR FRIDAY INTO
THE WEEKEND.  DSH

&&

.AVIATION...GUSTY WIND THIS AFTERNOON BUT ALIGNS WITH MAIN RUNWAYS
EVERYWHERE EXCEPT KSUN. CLOUDS WILL START TO MOVE IN SHORTLY AFTER
20/18Z...SO SUNDAY WILL BE A LARGE CHANGE IN THE FORECAST COMPARED
TO WHAT SAT HAS BEEN. SUNDAY SHOULD HAVE AFTERNOON -TSRA IN KSUN
KPIH AND KBYI AT LEAST IN THE VCNTY. MESSICK

&&

.FIRE WEATHER...WILL LET CURRENT RED FLAG CONTINUE AS CONDITIONS ARE
NEARLY MET IN THE VALLEY LOCATIONS AT LEAST. THE NORTHWEST FLOW THAT
HAS KEPT THE LAST TWO DAYS VERY DRY AND WINDY WILL RETREAT TO THE
NORTH AS HIGH PRESSURE STRENGTHENS IN THE DESERT SOUTHWEST. THE MORE
SOUTHERLY FLOW IS EXPECTED TO BRING IN SOME MOIST UNSTABLE AIR AND
SO THUNDERSTORMS ARE EXPECTED BY EARLY SAT AFTERNOON AND CONTINUE
LATE NIGHT SUN. THE THUNDERSTORMS WILL BE MAINLY ACTIVE IN THE
SOUTHERN AND NORTHERN SAWTOOTH FOREST ZONES...THUS HAVE ISSUED RED
FLAG WARNING FOR LIGHTNING ACTIVITY IN ZONES 422 AND 427. THE
INCREASING MOISTURE WILL KEEP SOUTHERN AREAS FROM REACHING CRITICAL
HUMIDITY LEVELS...AND THE CLOUD COVER SHOULD LIMIT CONVECTION AND
PREVENT STRONG WINDS FROM REACHING THE SURFACE. THUS DO NOT BELIEVE
THAT RED FLAG FOR HUMIDITY AND WIND WILL BE NECESSARY.

MON WILL SEE CONTINUE INFILTRATION OF THIS MOIST UNSTABLE AIR AND
WOULD EXPECT A GREATER COVERAGE OF THUNDERSTORMS FOR MON AFTERNOON.
HOWEVER...TO AVOID CONFUSION WILL LIMIT RED FLAGS TO NEXT 36 HOURS.
FOR THE REST OF THE WEEK...UPPER LEVEL TROUGHING AT THE COAST WILL
KEEP THE STORM TRACK OVER THE WESTERN ZONES OF THE FORECAST AREA ON
TUE...BUT THIS TROUGH PASSES TO THE WEST ON THU...BRINGING A WIND
EVENT POSSIBLY ON WED BUT AT LEAST ON THU. COOLER...DRIER...AND
CONTINUED BREEZY FOR FRI AND THE WEEKEND IN FLAT ZONAL FLOW. MESSICK

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING IDZ410-425.

LAKE WIND ADVISORY UNTIL 9 PM MDT THIS EVENING IDZ021.

RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING IDZ427.

RED FLAG WARNING FROM 1 PM SUNDAY TO 6 AM MDT MONDAY IDZ427.

RED FLAG WARNING UNTIL 9 PM MDT THIS EVENING IDZ422.

RED FLAG WARNING FROM 4 PM SUNDAY TO 6 AM MDT MONDAY IDZ422.

&&

$$







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