Prognostic Meteorological Discussion
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000 FXUS02 KWBC 261605 PMDEPD EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1205 PM EDT TUE JUL 26 2016 VALID 12Z FRI JUL 29 2016 - 12Z TUE AUG 02 2016 ...OVERVIEW/GUIDANCE EVALUATION/UNCERTAINTY ASSESSMENT... TO COMMENCE THE MEDIUM RANGE PERIOD...THE SYNOPTIC PATTERN WILL FEATURE A LONGWAVE TROUGH EXTENDING FROM THE MIDDLE MS VALLEY INTO THE GREAT LAKES/INTERIOR NORTHEAST. MULTIPLE EMBEDDED SHORTWAVES SHOULD SLOWLY MIGRATE NORTHEASTWARD TOWARD THE MID-ATLANTIC/NEW ENGLAND COAST...EACH BEING A FOCI FOR ORGANIZED CONVECTION. A LEAD SURFACE LOW EXITING THE DELMARVA PENINSULA ON FRIDAY MORNING IS DEPICTED SOMEWHAT DIFFERENTLY AMONG THE MODELS. WHILE THE 06Z/00Z GFS AND 00Z ECMWF AGREE ON THE POSITION NEAR SOUTHERN NJ ON 29/1200Z...RECENT GFS SOLUTIONS HAVE BEEN CONSIDERABLY DEEPER WITH A DEFINED WAVE CONTINUING INTO THE WESTERN ATLANTIC. MEANWHILE...THE 00Z CMC/UKMET ARE WELL BACK TO THE WEST WITH LITTLE TO NO ENSEMBLE SUPPORT EVIDENT. RESIDUAL TROUGHING EXISTS INTO THE WEEKEND OVER THE GREAT LAKES/OH VALLEY WITH THE GUIDANCE AT ODDS REGARDING TIMING AND HOW TO ORIENT THE SHORTWAVE ENERGY. LIKE RECENT DAYS...THE GFS SOLUTIONS HAVE BEEN QUICKER TO ADVANCE THE HEIGHT FALLS TOWARD THE NORTHEASTERN U.S. WHILE THE 00Z CMC TRIES TO SPLIT THE SYSTEM INTO SEPARATE ENTITIES. THE SLOWER AND CONSISTENT ECMWF CAMP APPEARS TO BE THE WAY TO PROCEED...PARTICULARLY THE 00Z ECMWF ENSEMBLE MEAN FROM DAY 5 ONWARD GIVEN THE STABILITY OF ITS FORECAST. HOWEVER...THE DAY 3/4...FRIDAY/SATURDAY FORECAST WAS CONSTRUCTED BY A MIX OF THE 06Z GFS/00Z ECMWF GIVEN SIMILAR SOLUTIONS. ALTHOUGH DID RAISE PRESSURES SLIGHTLY IN THE EXITING LOW OFF OF NJ. ELSEWHERE ON THE MAP...A DOMINANT CLOSED UPPER HIGH WILL REMAIN IN PLACE OVER THE DESERT SOUTHWEST WITH GRADUAL WEAKENING INTO DAY 4/SATURDAY AS HEIGHTS LOWER ACROSS THE WEST COAST. THE 00Z UKMET REMAINS MORE ROBUST INTO THE WEEKEND MAINTAINING AN EXPANSIVE 594-DM CONTOUR. TO ITS NORTH...THERE ARE STRONG INDICATIONS OF A COMPACT CYCLONIC CIRCULATION DRIFTING TOWARD THE SAN FRANCISCO BAY AREA DURING THE SATURDAY THROUGH MONDAY TIMEFRAME. WHERE THE GUIDANCE IS MORE UNCERTAIN IS WITH HEIGHT FALLS DIGGING INTO THE PACIFIC NORTHWEST ON SUNDAY. RECENT ENSEMBLE SPAGHETTI PLOTS SHOW VARIOUS SOLUTIONS IN PLAY WITH THE 00Z CMC STANDING OUT AS AN OUTLIER GIVEN ITS EXTENT OF AMPLIFICATION. ITS MORE PRONOUNCED SHORTWAVE DISAGREES WITH THE CONSENSUS OF ENSEMBLE MEANS. CONSIDERING OTHER MODELS...RECENT MODELS HAVE STRUGGLED TO DEPICT HOW QUICKLY THESE IMPULSES WILL TRACK ACROSS WESTERN/CENTRAL CANADA WHICH ULTIMATELY DICTATES THE PACE OF THE COLD FRONT. THE 06Z GFS FORMS A REX BLOCK OVER WESTERN CANADA WHICH LEADS TO A SLOWER PROGRESSION OF THE UPPER TROUGH. THE MORE PROGRESSIVE 00Z ECMWF/ECMWF ENSEMBLE MEAN HAS CONSISTENCY ON ITS SIDE WITH MODEST SUPPORT FROM THE 00Z CMC/NAEFS ENSEMBLE MEANS. AS SUCH...LEANED MORE IN THE DIRECTION OF THE ECMWF CAMP...ROUGHLY 70 PERCENT...RELATIVE TO THE 00Z NAEFS MEAN. REMOVED ANY DETERMINISTIC INFLUENCES BEYOND DAY 5.5/SUNDAY EVENING GIVEN GROWING UNCERTAINTY IN THE GLOBAL CIRCULATIONS. ...SENSIBLE WEATHER HIGHLIGHTS... GIVEN THE UPPER HIGH ANCHORING THE SOUTHWESTERN U.S. EARLY IN THE PERIOD...ABOVE NORMAL TEMPERATURES ARE EXPECTED WITH ANOMALIES IN THE 5 TO 10 DEGREE RANGE. IN PARTICULAR...HIGHS ON FRIDAY WILL RANGE FROM 110 TO 115 DEGREES ACROSS THE DESERT SOUTHWEST WITH WIDESPREAD 100 DEGREE PLUS READINGS OVER VALLEY LOCALES EXTENDING INTO THE CENTRAL GREAT BASIN. AS THE UPPER TROUGH TAKES SHAPE OVER THE NORTHWESTERN U.S...LOWERING HEIGHTS SHOULD HELP DECREASE SOME OF THESE HIGHER ANOMALIES. ELSEWHERE...A PERSISTENT THREAT FOR SHOWERS AND THUNDERSTORMS OVER THE NORTHERN/CENTRAL PLAINS EASTWARD TO THE MIDDLE MS VALLEY SHOULD MAINTAIN COOLER WEATHER WITH HIGHS GENERALLY IN THE LOW/MID 80S. IN GENERAL...UNSETTLED CONDITIONS ARE LIKELY IN PROXIMITY OF THIS MEANDERING FRONTAL ZONE FROM THE GREAT PLAINS TO THE MID-ATLANTIC COAST. OTHERWISE...EXPECT ABUNDANT WARM SECTOR...DIURNALLY DRIVEN THUNDERSTORMS TO FORM EACH DAY. AND LOOKING INTO THE DESERT SOUTHWEST...EXPECT AN INCREASE IN MONSOONAL THUNDERSTORMS BY LATE IN THE WEEKEND INTO EARLY NEXT WEEK. RUBIN-OSTER $$

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