083
FXUS10 KWNH 280443
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1243 AM EDT TUE APR 28 2020
VALID APR 28/0000 UTC THRU MAY 1/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
DEPARTING NORTHEAST STORM SYSTEM THROUGH TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: HIGH
THE EXITING COASTAL LOW FROM NEW ENGLAND WILL PASS SOUTH OF NOVA
SCOTIA THROUGH TUESDAY AS IT CONSOLIDATES INTO A STRONGER LOW
SOUTH OF NEWFOUNDLAND BY TUESDAY NIGHT. DETERMINISTIC MODEL
SPREAD IS MINIMAL AND THEREFORE A GENERAL MODEL BLEND WILL
CONTINUE TO WORK WELL FOR THIS REGION.
STRONG STORM SYSTEM DEVELOPING OVER THE NORTH-CENTRAL U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z ECMWF/ECENS WITH LESSER WEIGHTING TO
THE 12Z UKMET
CONFIDENCE: AVERAGE
A NORTHERN STREAM SHORTWAVE TROUGH IS AMPLIFYING ACROSS MONTANA
AND THE DAKOTAS IN RESPONSE TO A DEEP LAYER RIDGE DEVELOPING OVER
THE WESTERN U.S. AND SOUTHWEST CANADA, AND THIS WILL CONTINUE
GOING THROUGH THE MIDDLE OF THE WEEK. A WELL DEVELOPED CLOSED LOW
IS FORECAST TO EVOLVE OVER THE MIDWEST AND THEN THE SOUTHERN GREAT
LAKES BY WEDNESDAY NIGHT AS A DEEP LAYER TROUGH ENVELOPS MUCH OF
THE EASTERN U.S. BY THAT TIME PERIOD. ALL OF THE MODELS SHOW
REASONABLY GOOD AGREEMENT WITH THE UPPER LEVEL EVOLUTION AND
SURFACE CYCLOGENESIS GOING THROUGH WEDNESDAY MORNING. BY EARLY
THURSDAY, SOME LATITUDINAL DIFFERENCES BECOME APPARENT AS THE 00Z
NAM/GFS SOLUTIONS HAVE THE SURFACE LOW OVER CENTRAL MICHIGAN, AND
THE 12Z NON-NCEP SOLUTIONS TENDING TO KEEP THE LOW FARTHER TO THE
SOUTHEAST, AND WITH A BIT BETTER DEFINED TRIPLE-POINT LOW OVER THE
MID-ATLANTIC STATES AT THE END OF THE PERIOD GIVEN PLACEMENT OF
STRONGER HEIGHT FALLS FOCUSING STILL A TAD FARTHER SOUTH, WITH THE
UKMET ON THE SOUTHERN EDGE OF THE GUIDANCE SPREAD THROUGH
WEDNESDAY EVENING.
PAIR OF SHORTWAVE TROUGHS FOR THE NORTHWESTERN U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/00Z GFS/12Z UKMET
CONFIDENCE: ABOVE AVERAGE
A MODEST AND RATHER PROGRESSIVE SHORTWAVE TROUGH FROM THE NORTH
PACIFIC IS EXPECTED TO CLIP WASHINGTON STATE AND REACH SOUTHERN
BRITISH COLUMBIA BY LATE TUESDAY. A WEAKENING COLD FRONT IS
EXPECTED TO ACCOMPANY THIS SHORTWAVE FEATURE AS IT HEADS INTO AN
UPPER LEVEL RIDGE AXIS, ALTHOUGH THE PARENT SURFACE LOW WILL PASS
WELL TO THE NORTH NEAR THE SOUTHEAST ALASKA PANHANDLE. IN TERMS
OF THE LATEST MODEL GUIDANCE, THERE IS NOW ENOUGH MODEL AGREEMENT
TO SUPPORT A GENERAL MODEL BLEND FOR THIS FIRST WAVE.
A SECOND SHORTWAVE DISTURBANCE WILL TRACK JUST BEHIND IT AND
SHOULD REACH THE PACIFIC NORTHWEST ON THURSDAY, WITH THE FRONT
MOVING INLAND ACROSS PORTIONS OF THE WEST. THE GUIDANCE REFLECTS
A RELATIVELY LOW-AMPLITUDE TO THIS SYSTEM AT LEAST THROUGH THIS
PERIOD, WITH THE NAM AND UKMET INITIALLY A LITTLE STRONGER AS THE
SYSTEM APPROACHES THE COAST, AND THE CMC IS QUICKER WITH THE
PROGRESSION OF THE FRONT. ALTHOUGH THE 00Z GFS IS SLIGHTLY MORE
AMPLIFIED ALOFT, IT IS IN BETTER AGREEMENT COMPARED TO EARLIER
RUNS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
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