Prognostic Meteorological Discussion
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000 FXUS02 KWBC 191556 PMDEPD EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1056 AM EST SUN NOV 19 2017 VALID 12Z WED NOV 22 2017 - 12Z SUN NOV 26 2017 ...RECORDS HIGHS LIKELY IN THE SOUTHWEST LATER THIS WEEK... ...WET OVER THE NORTHWEST... ...OVERVIEW... STRONG UPPER HIGHS NEAR SAN DIEGO AND THE DAVIS STRAIT BETWEEN FAR NORTHEASTERN CANADA AND GREENLAND WILL FAVOR EASTERN US TROUGHING AND COOLER THAN AVERAGE TEMPERATURES. RECORD WARM TEMPERATURES ARE LIKELY FOR PARTS OF THE SOUTHWEST BUT WEST TO SOUTHWESTERLY FLOW INTO THE PACIFIC NORTHWEST WILL MAINTAIN A RATHER WET PATTERN. ADDITIONAL WET WEATHER IS LIKELY OVER FLORIDA ASTRIDE A SLOWLY MOVING FRONTAL BOUNDARY. THE MIDDLE PART OF THE COUNTRY IS EXPECTED TO BE RATHER DRY AND MILD TO START BUT TRENDING COOLER BY THE WEEKEND. ...GUIDANCE/UNCERTAINTY PREFERENCES...... MODELS/ENSEMBLES ARE IN GOOD AGREEMENT ON THE LARGE SCALE PATTERN BUT DIFFER ON SOME TIMING/AMPLITUDE DETAILS. THERE REMAINS SOME 00Z/12Z GUIDANCE OSCILLATING BUT OVERALL THE LATEST 00Z GUIDANCE WAS RATHER AGREEABLE AND A BLEND OF THE RECENT GFS/ECMWF/CANADIAN/UKMET OFFERED A GOOD STARTING POINT FOR THE WED/THU FORECAST. AFTER THAT, THE GFS DEPARTED FROM THE ECMWF/CANADIAN/ENSEMBLE CLUSTERING OVER CANADA (BOTH NEAR THE BORDER AND FARTHER NORTH INTO THE NW TERRITORIES/NUNAVUT) AND IT WAS DROPPED FROM THE PREFERENCE. PREVIOUS GEFS RUNS WERE CLOSER TO THE ECMWF ENSEMBLES SO THE 00Z GEFS MAY BE JUST A JOG FROM OTHERWISE DECENT CONTINUITY. TREND HAS BEEN WAVERING IN THE GULF TOWARD EITHER A CLOSED LOW OR WEAKLY SEPARATED TROUGH MOVING ACROSS FLORIDA LATER IN THE WEEK, BUT STILL FAVORED A BIT STRONGER SOLUTION GIVEN THE STRENGTH OF THE UPPER HIGH BOTH UPSTREAM AND DOWNSTREAM. TO THE WEST, CANADIAN AND GFS STILL SHOWED A SHORTWAVE MOVING INTO CALIFORNIA SAT WHILE THE ENSEMBLE TREND HAS BEEN TO HAVE THIS ONLY SLOWLY MOVE EASTWARD LIKE THE 00Z ECMWF/CONTINUITY, DEPICTED AS THE APPROACHING BUT WEAKENING COLD FRONT NEXT SUNDAY WEST OF SAN FRANCISCO. TO THE EAST, FAVORED THE MORE AMPLIFIED/COOLER ECMWF ENSEMBLE SOLUTION NEXT WEEKEND WHICH SHOULD FOLLOW BEHIND A COLD FRONT MOVING OFF THE EAST COAST. ...WEATHER HIGHLIGHTS... OCCASIONALLY HEAVY DAILY RAINS AND LOCALLY HEAVY ELEVATION SNOWS WILL PERSIST IN THE PAC NW THIS WEEK, PERHAPS EASING THIS COMING WEEKEND DEPENDING ON HOW QUICKLY THE NEXT SYSTEM MOVES TOWARD THE COAST. UPPER RIDGING WILL SUPPORT WELL ABOVE AVERAGE TEMPERATURES IN THE SOUTHWEST WHERE RECORD HIGHS ARE POSSIBLE WED-SAT OVER PARTS OF CA/NV/AZ/UT. MILD TEMPERATURES WILL EXTEND EASTWARD THROUGH THE CENTRAL/SOUTHERN ROCKIES AND PLAINS AHEAD OF A COLD FRONT THU/FRI WITH COOLER TEMPERATURE TO FOLLOW FOR THE WEEKEND. THERE IS A GOOD CHANCE FOR APPRECIABLE PRECIPITATION ALONG THE GULF COAST AS LOW PRESSURE CENTERS MEANDER ALONG A SLOW MOVING FRONT. EXPECT SOME RAIN/SNOW AROUND THE GREAT LAKES BUT GENERALLY NO PRECIPITATION FROM THE SOUTHWEST TO THE PLAINS AND MS VALLEY. ...THANKSGIVING FORECAST... IT WILL REMAIN GENERALLY QUIET FOR MOST OF THE LOWER 48. PRECIPITATION WILL BE MOST CONCENTRATED IN THE PACIFIC NORTHWEST INTO NORTHERN CALIFORNIA AS WELL AS NORTHERN IDAHO/WESTERN MONTANA/NW WYOMING. SCATTERED TO PERHAPS WIDESPREAD RAIN IS ALSO QUITE POSSIBLE THROUGH FLORIDA AND THE COASTAL SOUTHEAST DEPENDING ON HOW THE SURFACE SYSTEMS EVOLVE. RECORD HIGH TEMPS ARE LIKELY IN THE SOUTHWEST WITH 80S AND SOME 90S. PHOENIX HAS THE CHANCE OF RECORDING THEIR LATEST 90 DEGREE DAY SO LATE IN THE YEAR (RECORD IS NOV 15 1999) INCLUDING THEIR WARMEST THANKSGIVING DAY (RECORD IS 87 ON NOV 23 1950 AND NOV 27 2014 - THANKS TO THE PHOENIX NWS OFFICE FOR THE CLIMATE/RECORD INFORMATION). COOLER 30S/40S IN THE UPPER MIDWEST/GREAT LAKES/NORTHEAST/MID-ATLANTIC ARE LIKELY BY NEXT WEEKEND BEHIND THE FRONT. FRACASSO/SCHICHTEL $$

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