Prognostic Meteorological Discussion
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000
FXUS10 KWNH 280635
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
234 AM EDT FRI APR 28 2017

VALID APR 28/0000 UTC THRU MAY 01/1200 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

00Z MODEL EVALUATION...FINAL MODEL PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


...LARGE UPPER TROUGH/FRONTAL SYSTEM EXITING THE GREAT LAKES/UPPER
MS VALLEY...
...COLD FRONT REACHING THE MID-ATLANTIC/NORTHEAST EARLY FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

ONLY VERY MODEST MASS FIELD SPREAD IS NOTED WITH THIS SYSTEM. A
GENERAL MODEL BLEND SHOULD SUFFICE.


...UPPER LOW OVER SOUTHERN ALBERTA MOVING SLOWLY EAST ACROSS
SASKATCHEWAN BY SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THERE ARE SOME MINOR TIMING/DEPTH DIFFERENCES WITHIN THE MODELS
WITH THIS SYSTEM AS IT SLOWLY MOVES EAST INTO SASKATCHEWAN BY
SAT...BUT THE MODELS AGREE IN DAMPENING THE ENERGY OUT BY SUN. A
GENERAL MODEL BLEND WILL BE PREFERRED.


...INITIAL TROUGH/HEIGHT FALLS OVER THE HIGH PLAINS ON FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z UKMET AND 00Z ECMWF
CONFIDENCE: AVERAGE

THERE WILL BE THE EMERGENCE OF SOME LEAD SHORTWAVE ENERGY AND
RESULTING HEIGHT FALLS OUT ACROSS THE CENTRAL HIGH PLAINS THROUGH
FRI WITH THE MODELS INDICATING A SMALL SCALE MID LEVEL LOW CENTER
NEAR THE CO/KS BORDER THAT WILL LIFT NORTH INTO WESTERN NEB. BY
FRI NIGHT...THIS ENERGY WILL WEAKEN IN LIEU OF STRONGER TROUGH
AMPLIFICATION BACK OVER THE FOUR CORNERS REGION. THE 00Z GFS
APPEARS TO BE A BIT TOO STRONG WITH THE LEAD ENERGY OVER WESTERN
NEB...WITH THE 00Z NAM AND THE 00Z NON-NCEP GUIDANCE ALL A TAD
WEAKER. THIS IS SUPPORTED BY THE 00Z GEFS MEAN AND 12Z ECENS MEAN
TOO. THE 00Z NAM THOUGH BEGINS HAVE ITS OWN APPARENT BREAK AWAY
FROM THE MODEL CONSENSUS BY FRI NIGHT/EARLY SAT OVER SOUTHWEST KS
WHERE IT SUGGESTS A STRONGER SMALL SCALE CLOSED 700 MB CENTER
EJECTING NORTHEAST FROM NEAR THE BORDER OF FAR SOUTHEAST CO AND
THE OK PANHANDLE. THIS DRIVES A SIGNIFICANT QPF DIFFERENCE BETWEEN
THE NAM AND THE GLOBAL MODEL CONSENSUS. THE 00Z UKMET AND 00Z
ECMWF TEND TO HAVE STRONG MODEL CLUSTERING AND ARE VERY CLOSE TO
THE MODEL CONSENSUS ACROSS THIS REGION...SO WILL PREFER A
UKMET/ECMWF BLEND FOR NOW FOR THE MASS FIELDS.


...AMPLIFYING TROUGH OVER THE INTERMOUNTAIN WEST...
...CLOSED LOW DEVELOPMENT OVER THE FOUR CORNERS REGION FRI/SAT...
...SYSTEM EJECTING ACROSS THE PLAINS/MIDWEST THROUGH SUN/MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF
CONFIDENCE: AVERAGE

THERE CONTINUES TO BE GOOD LARGE SCALE AGREEMENT WITH THE
EVOLUTION OF A LARGE CLOSED LOW/TROUGH EVOLVING ACROSS THE
CENTRAL/SOUTHERN ROCKIES AND INTO THE CENTRAL AND SOUTHERN PLAINS
THIS WEEKEND. BY EARLY NEXT WEEK...THE MODELS TAKE A STRONG CLOSED
LOW CENTER NORTHEAST ACROSS THE MIDWEST. LOW PRESSURE ASSOCIATED
WITH THIS SYSTEM WILL FOCUS OVER THE SOUTHERN PLAINS BEFORE THEN
LIFTING NORTHEAST ACROSS THE RED RIVER VALLEY AND THEN UP ACROSS
THE MID MS VALLEY AND UPPER MIDWEST. THE 00Z UKMET AGAIN INSISTS
ON TAKING ITS LOW AND MID LEVEL LOW CENTERS FASTER OFF TO THE
NORTHEAST AND ESPECIALLY BY SUN AND MON AS THE SYSTEM LIFTS OUT OF
THE PLAINS AND ACROSS THE MIDWEST. THE REMAINING MODELS ARE BETTER
CLUSTERED ON A SLIGHTLY SLOWER EVOLUTION BY COMPARISON. HAVING
SAID THAT...THE 00Z GFS IS A LITTLE FASTER THAN THE 00Z
ECMWF...AND THE 00Z NAM DOES TRACK A BIT MORE ENERGY TO THE LEFT
OR NORTH OF THE GFS/ECMWF CLUSTER. THE 00Z CMC IS NOW CLOSE TO A
BLEND OF THE GFS/ECMWF SOLUTIONS OVERALL. BASED ON THIS AND THE
ENSEMBLE MEAN SOLUTIONS...A BLEND OF THE GFS AND ECMWF WILL BE
MAINTAINED. ALSO OF NOTE...THIS LARGE SCALE CLOSED LOW EVOLUTION
WILL BE DRIVING SIGNIFICANT AND HIGH-IMPACT RAINFALL...INCLUDING
WIDESPREAD FLASH FLOODING...ACROSS PARTS OF THE PLAINS/MS VALLEY
AND THE OH VALLEY. PLEASE CONSULT THE LATEST QPFPFD AND QPFERD FOR
MORE DETAILS ON THESE IMPACTS.


...PACIFIC FRONTAL SYSTEM REACHING BRITISH COLUMBIA/PACIFIC
NORTHWEST SAT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE 00Z UKMET TRENDED CLOSER TO THE MODEL CONSENSUS WITH THIS NEXT
SYSTEM ADVANCING INTO THE PACIFIC NORTHWEST. GIVEN THE REASONABLY
GOOD MODEL CLUSTERING SEEN NOW WITH THE GUIDANCE...A GENERAL MODEL
BLEND WILL BE PREFERRED.


WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/

ORRISON

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