Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6
000 FXUS02 KWBC 191457 PMDEPD EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1057 AM EDT FRI SEP 19 2014 VALID 12Z MON SEP 22 2014 - 12Z FRI SEP 26 2014 ...OVERVIEW AND PREFERENCES... THE MEDIUM RANGE WILL BE CHARACTERIZED BY ANOTHER COLD FRONT MOVING ACROSS THE EAST EARLY IN THE FORECAST...WITH HIGH PRESSURE MOVING IN AND THEN BEING REINFORCED THROUGH DAY 7/FRIDAY. AN UPPER TROUGH MOVING ACROSS THE NORTHEAST US ON DAYS 3 TO 5/MONDAY TO WEDNESDAY... WILL LIFT NORTHEASTWARD INTO EASTERN CANADA BY DAY 7/FRIDAY. ACROSS THE REST OF THE NATION...LARGE CHANGES WILL BE UNDERWAY AS A DEEPENING TROUGH TAKES HOLD ALONG THE WEST COAST. ALTHOUGH THERE IS A MINOR UPPER TROUGH EXPECTED TO MOVE EAST NORTHEASTWARD WITHIN THE MEAN RIDGE FROM THE GREAT BASIN ACROSS THE NORTHERN ROCKIES AND NORTHERN PLAINS STATES BY DAY 5/WEDNESDAY THAT THEN GETS SHEARED ALONG THE US CANADIAN BORDER...A LARGE UPPER LEVEL RIDGE IS EXPECTED TO EXPAND ACROSS A WIDE AREA OF THE NATION LATE IN THE FORECAST WITH THE EXCEPTION OF THE WEST. IN GENERAL...THE OPERATIONAL MODELS ARE IN VERY GOOD AGREEMENT WITH THE ENSEMBLE MEANS ON DAY 3/MONDAY WITH THE SLIGHT EXCEPTION THAT THE OPERATIONAL RUNS SUCH AS THE 00Z ECMWF HAS SLIGHT MORE DETAIL/DEPTH WITH THE EASTERN TROUGH. BY DAY 4...THERE CONTINUES TO BE FINE AGREEMENT ALTHOUGH THE 00Z CANADIAN APPEARS WAY TOO AMPLIFIED WITH A TROUGH OVER THE EAST. THIS AGREEMENT CONTINUES THROUGH WEDNESDAY/DAY 5. BY DAY 6/THURSDAY...THE OPERATIONAL AND ENSEMBLE CANADIAN RUNS VEER QUITE FAR FROM THEIR RESPECTIVE ECMWF/GFS/GEFS MEANS WHILE ON DAY 7...LARGER DIFFERENCES START TO SHOW UP IN BOTH THE OPERATIONAL RUNS AND MEANS. TAKING THIS INFORMATION INTO ACCOUNT...A BLEND OF THE 00Z ECMWF/ECMWF ENSEMBLE MEAN AND THE 06Z GFS/GEFS MEAN WERE ALL USED TO GENERATE THE FORECAST WITH THE OPERATIONAL RUNS CONTRIBUTING MORE TO THE BLENDS THROUGH DAY 5 WHILE THE ENSEMBLE MEANS HAD MORE INFLUENCE BY DAY 7. IN GENERAL...THE LARGEST DIFFERENCES ARE OBSERVED LATER IN THE FORECAST WITH THE WESTERN TROUGH BUT IN GENERAL...THIS WAS NOT A DIFFICULT FORECAST TO MAKE. ...SENSIBLE WEATHER HIGHLIGHTS... WITH A COLD FRONT APPROACHING THE EAST COAST ON MONDAY/DAY 3...SHOWERS ARE LIKELY FROM THE MIDDLE ATLANTIC STATES INTO THE NORTHEAST BUT THE FRONT LOSES ITS MOISTURE SOURCE IN THE SOUTHEAST. THE WEAK TROUGH MOVING WITHIN THE RIDGE FROM THE GREAT BASIN TO THE NORTHERN PLAINS WILL PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS IN THOSE REGIONS AS IT MOVES SLOWLY EAST NORTHEASTWARD TOWARD THE NORTHERN PLAINS BEFORE WEAKENING ON THURSDAY INTO FRIDAY. COMMENSURATELY...THE SHOWER ACTIVITY WILL LIKELY DROP OFF AS WELL. THIS REGION SHOULD SEE RELATIVELY WARM CONDITIONS ALTHOUGH CLOUDS WILL LIKELY TO KEEP AFTERNOON TEMPERATURES DOWN. IN THE WEST...COOLER AIR AND AN INCREASED CHANCE OF RAIN AND SHOWERS ARE EXPECTED BY MIDWEEK AS A RATHER LARGE OCEANIC STORM TAKES UP RESIDENCE OFF THE NORTHWEST COAST. KOCIN $$

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