499
FXUS10 KWNH 181858
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
157 PM EST TUE FEB 18 2020
VALID FEB 18/1200 UTC THRU FEB 22/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 48 HOURS; 06Z GEFS, 00Z
ECMWF/ECENS BLEND THEREAFTER
CONFIDENCE: AVERAGE TO SLIGHTLY ABOVE AVERAGE, EXCEPT BELOW
AVERAGE FOR NC/VA COASTAL SYSTEM DAY 3
19Z UPDATE: NO SIGNIFICANT DIFFERENCES NOTED WITH THE 12Z GUIDANCE
THROUGH 48 HOURS BUT THERE REMAINS DISCREPANCY WITH THE GUIDANCE
ON DAY 3 ACROSS THE MID-ATLANTIC AND SOUTHEAST US. THE NON-NCEP
GUIDANCE STILL FAVORS A COASTAL LOW SUPPRESSED AND FURTHER
OFFSHORE, KEEPING ANY DEEP MOISTURE FROM NOT PULLING BACK INTO
PORTIONS OF NC/VA. GIVEN THE LOWER CONFIDENCE AND FORECAST
UNCERTAINTY, THE PREFERENCE IS TO LEAN TOWARD THE ENSEMBLE MEANS
ON DAY 3 FOR THAT AREA. OTHERWISE, THE REST OF THE CONUS IS IN
GOOD SHAPE WITH A GENERAL MODEL BLEND.
POSITIVELY TILTED TROUGH AXIS CURRENTLY ACROSS PORTIONS OF THE
CENTRAL/EASTERN US IS EXPECTED TO SLOWLY ADVANCE EASTWARD THROUGH
THE NEXT COUPLE OF DAYS AS A NORTHERN STREAM SHORTWAVE DROPS FROM
THE CANADIAN ROCKIES INTO THE GREAT LAKES REGION BY DAY 2.
UPSTREAM RIDGING WILL BUILD ACROSS THE WESTERN US AND INTERIOR
ROCKIES FOR DAY 2 INTO PORTIONS OF DAY 3 BEFORE A CLOSED LOW
SLIDES DOWN OFFSHORE THE WEST COAST. THE SURFACE PATTERN WILL BE
REFLECTED BY A LARGE DOME OF ARCTIC HIGH PRESSURE OVER THE
CENTRAL/EASTERN US. TOWARD THE END OF DAY 3, A LOW PRESSURE MAY
FORM OFF THE NC COAST.
THROUGH 48 HOURS, A GENERAL MODEL BLEND IS PREFERRED AS FOR THE
LARGE SCALE MASS FIELDS THERE IS RELATIVELY LITTLE SPREAD SEEN
FROM A DETERMINISTIC PERSPECTIVE AND THE ENSEMBLE SPREAD IS FAIRLY
LOW. FOR DAY 3, THE MOST NOTABLE MODEL SPREAD LIES ACROSS THE
SOUTHEASTERN US AND WHERE A POTENTIAL LOW FORMS (AND ITS
IMPLICATIONS FOR WINTER WEATHER ACROSS NC/VA). FOR NOW, THE NAM
AND GFS WERE CONSIDERED LESS USEFUL AND NOT INCLUDED IN THE
PREFERRED BLEND DUE TO ITS BIAS FOR DEEPER MOISTURE BEING PULLED
BACK TO NW. THE BEST CONSENSUS APPROACH FAVORED THE 06Z GEFS MEAN
AND 00Z ECMWF/ECENS MEAN. THOUGH IT'S IMPORTANT TO POINT OUT THAT
THE DAY 3 FORECAST FOR THE SOUTHEAST IS A LOW CONFIDENCE FORECAST.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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