Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 291929
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
129 PM MDT WED APR 29 2015

.SHORT TERM...TONIGHT THROUGH SATURDAY.

COLD FRONT STILL EXPECTED TO ARRIVE LATE THIS AFTERNOON AND EVENING.
EXPECT ISOLATED SHOWERS AND THUNDERSTORMS TO DEVELOP ALONG THE
MOUNTAINS AND HIGHLANDS AS THE FRONT MOVES THROUGH THE REGION.
MODELS STILL INDICATE THAT A FEW SHOWERS COULD DRIFT INTO THE SNAKE
PLAIN THIS EVENING. NOT MUCH MOISTURE TO WORK WITH...EXPLAINS WHY
COVERAGE WILL REMAIN ISOLATED. THE THREAT FOR SHOWERS WILL QUICKLY
EXIT THE AREA THURSDAY MORNING. EXPECT TEMPS TO BE ABOUT 10 DEGREES
COOLER ON THURSDAY. WARMER WEATHER WILL RETURN FOR FRIDAY WITH MANY
LOCATIONS IN THE MID 70S ONCE AGAIN. MODELS NOW INDICATING A VERY
WEAK FEATURE WORKING NORTHWARD OUT OF UTAH ON SATURDAY WHICH COULD
PRODUCE A FEW SHOWERS AND THUNDERSTORMS ACROSS THE SOUTHERN
HIGHLANDS.

VALLE

.LONG TERM...SAT NIGHT THROUGH NEXT WED NIGHT. 500MB LONG WAVE
INDICATES A TROUGH CONTINUING IN CANADA AND THE NORTHERN PLAINS
THROUGH TUE...THEN THE LOW AMPLITUDE UPPER LEVEL RIDGE SLIDES
EASTWARD AND OVER THE GEM STATE BY LATE TUE NIGHT WITH A TROUGH TO
THE SOUTH OVER SOUTHERN GREAT BASIN. IT RESEMBLES SOMETHING OF A
SPLIT. THE WEAK FLOW...ESPECIALLY TOWARDS THE END...MAKES FOR A LOW
CONFIDENCE IN THE FORECAST...AND EXPLAINS THE LOW POPS FOR THE
VALLEY LOCATIONS IN THE GFS AND ECMWF. THE TIMING OF SHORTWAVE
THROUGH THE MEAN NORTHWESTERLY FLOW ALSO ADDS TO THE UNCERTAINTY.
THE GFS IS 12 HOURS FASTER AND WETTER WITH A SHORTWAVE FOR SUN/SUN
NIGHT...AND IS ALSO WETTER FOR THIS EVENT. HOWEVER...THE ECMWF
BRINGS IN MUCH MORE PRECIPITATION WITH A SHORTWAVE ON TUE AND THEN A
CLOSED LOW THAT MOVES IN FROM THE WEST ON WED. THE TIMING ON THE
PROGRESS OF THIS LOW IS ACTUALLY FASTER ON THE GFS...BUT MUCH DRIER
COMPARED TO THE ECMWF. HAVE TRIED TO SPLIT THE DIFFERENCE
BETWEEN THE TWO OUTPUTS. MESSICK

&&

.AVIATION...APPROACHING DRY COLD FRONT WILL BRING GUSTY AND SHIFTING
WINDS...BUT CIGS SHOULD STAY MID-LEVEL OR HIGHER. CHANCE OF
RECEIVING PRECIPITATION IS BETWEEN 10 AND 20 PERCENT SO HAVE KEPT IN
THE VCSH WORDING FOR THE LATE AFTERNOON/EARLY EVENING TODAY.
MESSICK

&&

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

$$


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