Area Forecast Discussion
Issued by NWS Pocatello, ID

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
000
FXUS65 KPIH 201957
AFDPIH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE POCATELLO ID
157 PM MDT SAT SEP 20 2014

.SHORT TERM...TONIGHT THROUGH MONDAY NIGHT. EARLY AFTERNOON
SATELLITE IMAGERY WAS SHOWING A LOW PRESSURE SYSTEM SPINNING OVER
THE SRN CALIFORNIA COAST THIS MORNING AS AN AMPLIFIED UPSTREAM
TROUGH ADVANCED THROUGH THE EASTERN PAC TOWARD THE NW COAST. THE
MODELS ARE IN FULL AGREEMENT THAT THE UPSTREAM TROUGH WILL DRIVE THE
CUT-OFF LOW POSITIONED OVER SRN CALIFORNIA NE THROUGH THE GREAT
BASIN SUNDAY AND ACROSS THE DIVIDE INTO NE WYOMING LATE MONDAY. THE
ATTENDING PRECIPITATION SHIELD IS EXPECTED TO SPREAD ACROSS THE SRN
IDAHO BORDER SUNDAY MORNING AND THE REMAINDER OF SE IDAHO SUNDAY
AFTERNOON/EVENING. DEEP LAYER MOISTURE WILL ACCOMPANY THE LOW INTO
THE REGION SUNDAY/SUNDAY NIGHT SUPPORTING MODERATE TO HEAVY SHOWERS
AT TIMES. IN FACT...THE 12Z NAM WAS SHOWING A CONCENTRATED BAND OF
SHOWERS ADVANCING NORTH ALONG THE WYOMING BORDER SUNDAY NIGHT WITH
0.75 INCHES OF LIQUID PRODUCTION IN SEVERAL OF THE 3-HRLY TIME STEPS
WHEREAS THE GFS WAS FURTHER SOUTH AND EAST WITH LIGHTER AMOUNTS OF
0.30 INCHES OVER A 6-HR PERIOD. NOT TOO EXCITED AT THIS POINT GIVEN
ALL THE RUN TO RUN DIFFERENCES IN DETAILS BUT WILL ADD A MENTION OF
HEAVY RAINFALL TO FORECAST FOR THAT TIME FRAME. DRIER CONDITIONS
FOLLOW MONDAY NIGHT AS THE LOW EJECTS EAST THROUGH WYOMING AND A
DRIER SW FLOW SETS UP ACROSS THE REGION. HUSTON

.LONG TERM...TUESDAY THROUGH NEXT SATURDAY. THE AMPLIFIED UPSTREAM
TROUGH ADVANCES INTO THE COASTAL WATERS TUESDAY/WEDNESDAY AS THE
DOWNSTREAM RIDGE EXPANDS ACROSS THE GREAT BASIN TUESDAY THROUGH
WEDNESDAY BRINGING WARMER CONDITIONS TO THE AREA. BEYOND THURSDAY
AFTERNOON...THE GFS AND ECMWF CONTINUE TO SHOW DIFFERENCES IN THE
TIMING...TRACK AND EVOLUTION OF THE INCOMING TROUGH. THE 12Z GFS WAS
RUNNING ABOUT 12HRS FASTER IN DRIVING THE NEGATIVELY TILTED TROUGH
INLAND THURSDAY NIGHT AND THEN SPINNING UP A CLOSED LOW CIRCULATION
OVER THE NRN GREAT BASIN FRIDAY/FRIDAY NIGHT WHICH THEN PROGRESSES
SLOWLY EAST ALONG THE SRN IDAHO BORDER SATURDAY PLACING SE IDAHO IN
A PRIME POSITION FOR PRECIPITATION. THE 00Z ECMWF IS CURRENTLY
FAVORING A SLOWER PROGRESSION WHICH HOLDS THE MAIN PRECIPITATION
BAND OVER OREGON THROUGH FRIDAY FOLLOWED BY THE CLOSED LOW
CIRCULATION DEVELOPING OVER NRN CALIFORNIA FRIDAY NIGHT WHICH SLOWLY
EJECTS NE THROUGH OREGON/WRN IDAHO SATURDAY/SUNDAY WHILE PRODUCING
COPIOUS AMOUNTS OF RAINFALL OVER SE IDAHO THROUGHOUT THE WEEKEND.
HUSTON
&&

.AVIATION...VFR CONDITIONS WITH LIGHT WINDS EXPECTED THROUGH THE
PERIOD. EP
&&

.FIRE WEATHER...DRY CONDITIONS ARE EXPECTED TODAY...BEFORE ANOTHER
LOW PRESSURE SYSTEM WILL MOVE INTO THE AREA TOMORROW. SHOWERS AND
THUNDERSTORMS ARE ANTICIPATED SUNDAY AND MONDAY...WHICH WILL KEEP
HAINES INDEX VALUES BELOW 4. HIGH PRESSURE WILL BUILD IN TUESDAY AND
WEDNESDAY AND BRING DRIER CONDITIONS ONCE AGAIN. EP
&&

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

$$









USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.