Prognostic Meteorological Discussion
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FXUS10 KWNH 261840
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
239 PM EDT THU MAR 26 2015

VALID MAR 26/1200 UTC THRU MAR 30/0000 UTC

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

12Z MODEL EVALUATION ALONG WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


FULL-LATITUDE TROUGH CROSSING THE EASTERN U.S. THROUGH FRI
STRONG COLD FRONT/ASSOCIATED SURFACE WAVES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/ECMWF/UKMET
CONFIDENCE: AVERAGE

RELATIVELY MINOR TIMING/STRENGTH DIFFERENCES REMAIN WITH THIS
SYSTEM. THE 12Z NAM IS WORTH NOTING FOR ITS LESS AMPLIFIED NATURE
REGARDING THE CORE OF AN UPPER TROUGH OVER WRN NEW YORK AND
PENNSYLVANIA BY SAT MORNING COMPARED TO THE REMAINING MODEL
CONSENSUS. THE NAM ALSO FALLS INTO THE MINORITY WITH THE
CORRESPONDING SURFACE LOW OFF OF THE NEW ENGLAND COAST...WHICH IS
PARTIALLY TIED TO A SHORTWAVE ACROSS THE SOUTHEAST SAT MORNING.
THE 12Z GFS/ECMWF REPRESENT TWO SLIGHTLY DIFFERENT CAMPS BUT HOLD
GOOD CONTINUITY WITH THEIR PREVIOUS RUNS AND A GFS/ECMWF BLEND
FALLS IN THE MIDDLE OF THE LATEST SPREAD. THE 12Z UKMET IS SIMILAR
TO THE GFS AND WILL BE ADDED TO THE PREFERENCE.


PROGRESSIVE SHORTWAVE REACHING THE PACIFIC NORTHWEST BY LATE FRIDAY
COLD FRONT MOVING THROUGH THE GREAT PLAINS THIS WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS WITH THE 00Z ECMWF OR 12Z UKMET
CONFIDENCE: SLIGHTLY BELOW AVERAGE

A STOUT UPPER RIDGE ANCHORING THE WESTERN U.S. WILL QUICKLY GIVE
WAY TO A PROGRESSIVE SHORTWAVE CROSSING THE PACIFIC NORTHWEST BY
FRIDAY NIGHT. THE ENSEMBLES SHOW GREATER AGREEMENT ACROSS THE
NORTHWEST SUN MORNING WITH RIDGING AND GENERALLY MORE AMPLITUDE TO
SHORTWAVE TROUGHING DOWNSTREAM ACROSS THE CNTRL PLAINS COMPARED TO
PREVIOUS RUNS...HOWEVER...THE 12Z ECMWF/CMC REMAIN ON THE
DEEPER/SLOWER EDGE OF THE LATEST ENSEMBLE SPREAD. TRENDS IN THE
DETERMINISTIC GUIDANCE POINT TOWARD TWO PIECES OF SHORTWAVE ENERGY
BY SUN EVENING WITH ONE OVER THE GREAT LAKES AND A
SECOND...POTENTIALLY OVER THE LOWER CNTRL PLAINS. THE 12Z ECWMF
HAS WEAKENED THE NORTHERN ENERGY FROM ITS 00Z RUN...BUT THE 12Z
UKMET REMAINS SOMEWHAT STRONGER...SIMILAR TO THE 00Z ECMWF.

GIVEN THE STRENGTH OF THE RIDGE CURRENTLY IN PLACE OVER THE WEST
COAST...SLOWER COULD BE BETTER...BUT JUST NOT AS AMPLIFIED AS THE
ECMWF/CMC. GREATER ENSEMBLE SUPPORT EXISTS FOR A TIMING/STRENGTH
BETWEEN THE 12Z GFS AND 00Z ECMWF/12Z UKMET. CONFIDENCE IS REDUCED
GIVEN UNCERTAINTY WITH HOW THE LATITUDINAL EXTENT OF THE SHORTWAVE
WILL INITIALLY INTERACT WITH THE RIDGE AS IT REACHES THE WEST
COAST FRI EVENING.


SHORTWAVES CROSSING THE DESERT SOUTHWEST ON SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS/12Z CMC
CONFIDENCE: BELOW AVERAGE

THIS FEATURE TIES IN WITH THE SRN EXTENT OF THE SHORTWAVE
REFERENCED IN THE ABOVE SECTION. CURRENTLY...THE 12Z GFS AND THE
12Z CMC ARE MOST SUPPORTED BY THE ENSEMBLE SPAGHETTI CHARTS. GIVEN
THE WIDE SPREAD SEEN IN THE DETERMINISTIC GUIDANCE...CONFIDENCE
REMAINS BELOW AVERAGE.


WSWLY FLOW INTO NRN PORTIONS OF THE PACIFIC NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

MODELS SHOW SIMILARLY HERE WITH RESPECT TO IMPACTS INTO WASHINGTON
STATE.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

OTTO

$$




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