349
FXUS10 KWNH 071845
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 PM EDT FRI AUG 07 2020
VALID AUG 07/1200 UTC THRU AUG 11/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
OVERALL WEATHER PATTERN ACROSS THE CONTINENTAL U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND, WEIGHTED TOWARD THE 12Z NAM/12Z
GFS/12Z ECMWF
CONFIDENCE: AVERAGE
..19Z UPDATE
THE 12Z ECMWF/UKMET/CMC DID NOT MAKE ANY SIGNIFICANT CHANGES FROM
THEIR 00Z CYCLES. THERE ARE NO CHANGES TO THE PREFERENCE, OTHER
THAN TO REPLACE THE 00Z ECMWF WITH THE 12Z ECMWF.
..PREVIOUS DISCUSSION FOLLOWS
THE OVERALL PATTERN ACROSS THE LOWER 48 WILL FEATURE A BROAD UPPER
RIDGE CENTERED OVER THE SOUTHERN PLAINS INTO NORTHWESTERN MEXICO.
THE MAIN DRIVER OF SYNOPTIC SCALE FRONTS/LOWS WILL BE WITH THE JET
STREAM FOCUSED NEAR THE U.S./CANADIAN BORDER.
AN INITIAL QUASI-STATIONARY FRONT WILL REMAIN DRAPED FROM THE
MID-ATLANTIC TO THE LOWER MISSISSIPPI VALLEY. ALOFT, A WEAKENING
UPPER LEVEL TROUGH OVER THE EASTERN 1/3 OF THE NATION TODAY WILL
QUICKLY TRACK INTO THE WESTERN ATLANTIC THROUGH SATURDAY. THE
MODELS ARE FAIRLY SIMILAR WITH THIS SCENARIO.
ACROSS THE NORTH-CENTRAL U.S., A COLD FRONT WILL MOVE THROUGH THE
DAKOTAS BY SATURDAY MORNING, STALL OVER SOUTH DAKOTA AND MINNESOTA
LATE SATURDAY AND LIFT NORTH AS A WARM FRONT INTO SUNDAY MORNING.
THIS BOUNDARY WILL BE INFLUENCED BY SHORTWAVES MOVING ABOUT A
LONGWAVE TROUGH/CLOSED LOW MOVING ACROSS CENTRAL CANADA. THE
MODELS SHOW GENERALLY GOOD AGREEMENT WITH THIS FEATURE, WITH ONLY
MINOR TIMING/AMPLITUDE DIFFERENCES. THE GREATER DIFFERENCES ARE
NOTED TO BE WITH CONVECTIVELY DRIVEN MID-LEVEL VORTICITY MAXIMA
AND MESOSCALE BOUNDARIES FROM HEAVY RAINFALL. THERE IS NO CLEAR
ANSWER AS TO WHICH MODEL OR CLUSTER OF MODELS WILL VERIFY BEST,
BUT THERE HAVE BEEN TRENDS IN THE GUIDANCE OVER THE PAST 24-36
HOURS FOR MORE DEFINITION TO THESE FEATURES NEAR THE 12Z NAM, 12Z
GFS AND 00Z ECMWF...WITH THE 00Z UKMET/CMC LESS DEFINED IN THE
MID-LEVELS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
OTTO
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