Prognostic Meteorological Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6

000
FXUS10 KWNH 280428
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1227 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...PRELIMINARY MODEL PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


...LARGE UPPER TROUGH/FRONTAL SYSTEM EXITING THE GREAT LAKES/UPPER
MS VALLEY...
...COLD FRONT REACHING THE MID-ATLANTIC/NORTHEAST BY 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 12Z UKMET AND 12Z 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 12Z NON-NCEP GUIDANCE ALL A TAD
WEAKER. THIS IS SUPPORTED BY THE 18Z 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 12Z UKMET AND 12Z
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 12Z 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 12Z UKMET BECOMES AN
OUTLIER IN TAKING ITS LOW AND MID LEVEL 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 UKMET
IS ALSO PROBABLY A LITTLE TOO DEEP AS WELL. THE REMAINING MODELS
ARE MUCH BETTER CLUSTERED WITH THEIR TIMING BY COMPARISON. HAVING
SAID THAT...THE 00Z GFS IS A LITTLE FASTER THAN THE 12Z
ECMWF...AND THE 00Z NAM DOES TRACK A BIT MORE ENERGY TO THE LEFT
OR NORTH OF THE GFS/ECMWF CLUSTER. THE 12Z CMC IS OCCASIONALLY
APPEARING A LITTLE TOO WEAK WITH ITS MID LEVEL CENTER. 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: NON-12Z UKMET BLEND
CONFIDENCE: AVERAGE

THE 12Z UKMET STANDS AS A NEAR OUTLIER TO THE SOUTH WITH A 500 MB
TROUGH AMPLIFYING ACROSS THE NORTHWEST COAST OF THE CONUS COMPARED
TO THE LATEST ENSEMBLE AND DETERMINISTIC SOLUTIONS. A NON 12Z
UKMET BLEND IS PREFERRED GIVEN THE RELATIVELY SIMILAR NON-12Z
UKMET SOLUTIONS.


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

ORRISON

$$





USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.