790
FXUS10 KWNH 250647
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 AM EDT WED MAR 25 2020
VALID MAR 25/0000 UTC THRU MAR 28/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
EAST COAST CYCLOGENESIS THROUGH WEDNESDAY NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: HIGH
THE SURFACE LOW THAT HAS BEEN TRACKING EASTWARD ACROSS THE
SOUTH-CENTRAL U.S. IS FORECAST TO REDEVELOP NEAR THE MID-ATLANTIC
COASTLINE AND THEN INTENSIFY AS IT TRACKS OUT TO SEA, LIKELY
TAKING A TRACK FARTHER OFFSHORE THAN THE RECENT NOR'EASTER THAT
AFFECTED NEW ENGLAND MONDAY NIGHT. THERE IS ENOUGH AGREEMENT IN
THE GUIDANCE TO MERIT THE USE OF A MULTI-MODEL BLEND, EVEN THOUGH
THE 12Z ECMWF IS SLIGHTLY SLOWER WITH TAKING THE LOW AWAY FROM THE
COAST.
LONGWAVE TROUGH OVER THE WESTERN U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND AFTER 12Z THURSDAY
CONFIDENCE: MODERATE
THE AMPLIFIED PATTERN OVER THE EASTERN PACIFIC WILL END UP
PRODUCING A POSITIVELY TILTED LONGWAVE TROUGH AXIS WHICH WILL
SLOWLY PROGRESS DOWN THE WEST COAST, AND THEN GRADUALLY MOVE
INLAND ACROSS THE DESERT SOUTHWEST BY FRIDAY MORNING AND REACH THE
ROCKIES BY SATURDAY MORNING. THIS WILL SUPPORT LEE CYCLOGENESIS
ACROSS THE WESTERN HIGH PLAINS ALONG THE EXISTING FRONTAL
BOUNDARY. THE MAIN DIFFERENCE HERE IS WITH THE 12Z UKMET BEING
SLOWER WITH THE PROGRESSION OF THE TROUGH ACROSS THE INTERMOUNTAIN
WEST, AND THUS THE EVOLVING SURFACE LOW IS WEST OF THE MODEL
CONSENSUS BY SATURDAY MORNING.
SHORTWAVE AND SURFACE COLD FRONT APPROACHING PACIFIC NORTHWEST
SATURDAY MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/00Z CMC/18Z GEFS MEAN
CONFIDENCE: MODERATE
A SHORTWAVE TROUGH ORIGINATING FROM ALASKA WILL TRACK
SOUTHEASTWARD ACROSS THE NORTHEAST PACIFIC AND REACH THE PACIFIC
NORTHWEST BY SATURDAY MORNING. THIS WILL BRING THE NEXT
SIGNIFICANT ROUND OF PRECIPITATION TO THIS REGION BY THE END OF
THE FORECAST PERIOD. MODEL DIFFERENCES BECOME APPARENT BY 00Z
SATURDAY WITH THE 12Z ECMWF BECOMING MORE AMPLIFIED, AND THE UKMET
A BIT WEAKER AND FASTER.
NORTHERN STREAM SHORTWAVES CROSSING SOUTHERN CANADA THIS WEEK
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/12Z CMC/18Z GEFS MEAN
CONFIDENCE: MODERATE
THERE WILL BE THREE SEPARATE SHORTWAVE PERTURBATIONS IN THE
NORTHERN STREAM NEAR THE CANADIAN BORDER THAT WILL BE PIVOTING
AROUND THE MAIN POLAR VORTEX OVER NORTHERN CANADA, WITH THE FIRST
CROSSING THE NORTHERN GREAT LAKES ON WEDNESDAY. THIS WILL RESULT
IN A COLD FRONT DROPPING SOUTHWARD ACROSS THE NORTHERN PLAINS AND
THE UPPER MIDWEST. ALTHOUGH THERE IS GOOD MODEL AGREEMENT WITH
THE LEAD WAVE, THERE ARE SOME TIMING AND AMPLITUDE DIFFERENCES
WITH THE NEXT SET OF DISTURBANCES TO MOVE THROUGH. THE GFS AND
NAM ARE STRONGER WITH THE THIRD WAVE, AND THE UKMET IS MORE
PROGRESSIVE. THE ECMWF AND CMC INDICATE A SIMILAR EVOLUTION WITH
SUPPORT FROM THE ENSEMBLE MEANS, SO A BLEND OF THESE SOLUTIONS
WITH THE GEFS MEAN SHOULD SERVE WELL AS A STARTING POINT.
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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