Prognostic Meteorological Discussion
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000
FXUS02 KWBC 261603
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1202 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 ABOVE 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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