Area Forecast Discussion
Issued by NWS Pocatello, ID

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000
FXUS65 KPIH 200854
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
254 AM MDT SAT SEP 20 2014

.SHORT TERM...TODAY THROUGH MON NIGHT. UPPER LEVEL RIDGE WILL PEAK
TODAY WITH WARM TEMPERATURES AND NEARLY CLEAR SKIES. THIS ALL
CHANGES OVERNIGHT WITH A CLOSED LOW MOVING IN FROM THE SOUTH. THE
NORTHERLY WIND WILL GENERATE UPSLOPE AND RAINFALL IN THE SOUTHERN
HIGHLANDS AND THE SNAKE RIVER PLAIN SOUTH OF THE SNAKE
RIVER...INCLUDING POCATELLO...TONIGHT. THIS WILL PEAK IN INTENSITY
SUN EVENING WITH SOME POTENTIALLY LARGE RAINFALL ACCUMULATIONS.
THIS AIR IS MOIST AND UNSTABLE AND WILL CONTINUE THUNDERSTORMS
INTO EARLY MON MORNING...THEN INTENSIFY AGAIN MON AFTERNOON.
PRECIPITABLE WATER READING ARE FORECASTED TO BE NEAR 1
INCH...WHICH USUALLY LEADS TO AT LEAST SOME LOCALIZED
FLOODING...ALL THE MORE SO WHEN THE ATMOSPHERE IS UNSTABLE. THE
ONLY FLY IN THE OINTMENT IS THAT THE CLOUD COVER COULD BE SO
ABUNDANT AS TO KEEP THE LID ON THE CONVECTION...WE WOULD NEED SOME
BREAKS IN THE CLOUDINESS TO MAXIMIZE PRECIPITATION. BELIEVE IT
BEST TO HOLD OFF FOR NOW...BUT MAY NEED A FLASH FLOOD WATCH FOR
SUN AFTERNOON INTO SUN EVENING. WITH THE APPROACHING
LOW...NORTHERLY WIND EXPECTED TODAY AND WILL CONTINUE...ALTHOUGH
MAY WEAKEN THIS AFTERNOON DUE TO THE DIURNAL EFFECT COUNTERACTING
THE NORTHEAST GRADIENT IN THE SNAKE RIVER PLAIN AT LEAST. MON
NIGHT WILL SEE A CLEARING AFTER ANOTHER ROUND OF SHOWERS AND
THUNDERSTORMS. MESSICK

.LONG TERM...TUE THROUGH FRI NIGHT. AFTER THE SUN/MON TROUGH
DEPARTS...A INTENSE LOW APPROACHES THE COAST AND AMPLIFIES THE
TROUGH-RIDGE PATTERN IN THE UPPER LEVELS. THIS WILL PROVIDE STRONG
RIDGING AND ALLOW A WARM UP AS THE LOW MOVES ONSHORE. THE
AMPLIFICATION SLOWS THE APPROACH...BUT THE ARRIVAL DAY OF THE
LOW...OR AT LEAST MOISTURE RELATED TO IT...IS HIGHLY UNCERTAIN.
THE GFS IS ITS CHARACTERISTICALLY FASTER...BY THU NIGHT AND FRI.
THE ECMWF IS SLOWER...WHICH DOES SEEM TO BE A BETTER IDEA WITH THE
CLOSED LOW SCENARIO. SO HAVE PAINTED WITH A BROAD BRUSH AFTER THU
AFTERNOON.  MESSICK

&&

.AVIATION...HIGH PRESSURE WILL PRODUCE LIGHT WINDS AND VFR
CONDITIONS ACROSS THE AREA TODAY.

VALLE

&&

.FIRE WEATHER...HIGH PRESSURE WILL PRODUCE DRY CONDITIONS ACROSS THE
AREA TODAY. A LOW PRESSURE SYSTEM WILL BRING SHOWERS AND
THUNDERSTORMS TO THE REGION FOR SUNDAY AND MONDAY. DRIER WEATHER
WILL RETURN FOR TUESDAY AND WEDNESDAY.

VALLE

&&

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

$$







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