Prognostic Meteorological Discussion
Issued by NWS

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

000
FXUS10 KWNH 171856
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 PM EDT THU AUG 17 2017

VALID AUG 17/1200 UTC THRU AUG 21/0000 UTC

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

...AN EVALUATION OF THE 12Z MODEL GUIDANCE ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...


...PRONOUNCED SHORTWAVE PUSHING TOWARD THE UPPER MIDWEST...
...ASSOCIATED DEEP SURFACE LOW/ATTENDANT COLD FRONT...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

WATER VAPOR IMAGERY SHOWED A COMPACT UPPER LOW LIFTING THROUGH
NORTHWESTERN WI WITH A TRAILING FRONTAL ZONE/MOISTURE PLUME
EXTENDING DOWN FROM THE GREAT LAKES INTO THE ARKLATEX. MODELS SHOW
THIS SYSTEM CONTINUING TO MOVE NORTHEASTWARD TOWARD SOUTHEASTERN
ONTARIO DURING THE NEXT 24 TO 30 HOURS WITH GENERAL AGREEMENT
NOTED. THIS WILL ULTIMATELY HELP USHER A FRONTAL ZONE EASTWARD
TOWARD THE I-95 CORRIDOR BY FRIDAY EVENING. OVERALL...FAIRLY GOOD
AGREEMENT EXISTS AMONG THE MODELS TO SUPPORT A GENERAL MODEL
COMPROMISE.


...TRAILING SHORTWAVE RACING FROM THE DAKOTAS TO THE NORTHEASTERN
U.S. THROUGH SUNDAY...

FINAL PREFERENCE: A NON-12Z/00Z CMC MODEL COMPROMISE
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

IN THE WAKE OF THE LEAD SYSTEM PUSHING INTO THE GREAT
LAKES...ANOTHER DISTURBANCE IS FORECAST TO PUSH THROUGH THE MIDDLE
MS VALLEY BY FRIDAY EVENING. COMPARED TO OTHER AVAILABLE
SOLUTIONS...THE 12Z CMC IS A BIT SLOWER RELATIVE TO THE CONSENSUS
ALTHOUGH IT DID TREND QUICKER IN THIS MODEL RUN. THIS DIFFERENCE
CONTINUES INTO THE WEEKEND AS THE HEIGHT FALLS PROJECT THROUGH NEW
ENGLAND LATER IN THE WEEKEND. PLAN ON STAYING THE COURSE WITH A
NON-12Z/00Z CMC MODEL COMPROMISE.


...IMPULSE LIFTING OUT OF NORTHERN MX REACHING SOUTHWESTERN NM BY
20/0000Z...

FINAL PREFERENCE: BLEND OF THE 12Z GFS/ECMWF
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

A RATHER POTENT LOOKING FEATURE IS EXPECTED TO COME OUT OF MX
WHILE CROSSING INTO SOUTHWESTERN NM BY SATURDAY EVENING. THERE ARE
A COMPLEX ARRAY OF SOLUTIONS WITH A VARIETY OF STRENGTHS AND
POSITIONS. FOR INSTANCE...THE 12Z NAM SITS FARTHEST TO THE NORTH
WHILE THE 12Z/00Z CMC ARE STILL OVER MX WHILE BEING WEAKER.
SOLUTIONS CONTINUE TO VARY WITH NOT THE BEST RUN-TO-RUN
CONTINUITY. WILL STICK WITH THE PREVIOUS PREFERENCE UNTIL THE
MODELS COME INTO SLIGHTLY BETTER AGREEMENT.


...BROAD LONGWAVE TROUGH EXTENDING OVER THE WESTERN HALF OF CANADA
FRIDAY THROUGH SUNDAY...
...COLD FRONT SWEEPING THROUGH THE NORTH-CENTRAL U.S. OVER THE
WEEKEND...

FINAL PREFERENCE: BLEND OF THE 12Z GFS/ECMWF
FORECAST CONFIDENCE: AVERAGE

A STRONG LONGWAVE TROUGH INITIALLY OVER THE NORTHEASTERN PACIFIC
WILL DROP SOUTHEASTWARD IN TIME. THE BETTER CORRIDOR OF HEIGHT
FALLS SHOULD SURGE EASTWARD REACHING MANITOBA BY SUNDAY MORNING.
AS NOTED WITH OTHER SYSTEMS...THE 12Z/00Z CMC ARE MUCH SLOWER THAN
THE MODEL CONSENSUS WHICH PLACES ITS COLD FRONT WELL TO THE WEST.
BY THE END OF THE FORECAST...THE 12Z NAM/UKMET BEGIN TO ACCELERATE
AHEAD OF THE OTHER GUIDANCE WHICH EVENTUALLY BECOME THE OTHER
EXTREME AMONG THE SUITE OF MODELS. IN PARTICULAR...THE 12Z UKMET
REALLY BEGINS TO JUMP AHEAD WHILE ALSO BEING MUCH MORE ROBUST IN
NATURE. THESE OUTLYING SOLUTIONS ARE FAIRLY WELL DOCUMENTED WITHIN
THE RECENT ENSEMBLE SPAGHETTI PLOTS. A BLEND OF THE 12Z GFS/00Z
SHOULD SUFFICE HERE GIVEN SOMEWHAT SIMILAR FORECASTS AND SITTING
WITHIN THE CENTER OF THE MODEL SPREAD.


...ELONGATED UPPER TROUGH POSITIONED OVER THE SOUTHWESTERN U.S.
LATE IN THE FORECAST...

FINAL PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: ABOVE AVERAGE

TOWARD THE END OF THE PERIOD...A BROAD UPPER TROUGH IS FORECAST TO
EXTEND ACROSS THE SOUTHWESTERN STATES. MODELS ARE IN DECENT
AGREEMENT WITH GOOD CLUSTERING AMONG THE ENSEMBLE MEMBERS VIA THE
582-DM SPAGHETTI PLOT. A GENERAL MODEL COMPROMISE IS WARRANTED
HERE.


www.wpc.ncep.noaa.gov/html/model2.shtml
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

RUBIN-OSTER



$$





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