Prognostic Meteorological Discussion
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FXUS10 KWNH 291730
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
130 PM EDT THU SEP 29 2016

VALID SEP 29/1200 UTC THRU OCT 03/0000 UTC

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

...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...


...EXTENSIVE UPPER LOW MEANDERING BETWEEN THE OH VALLEY AND THE
LOWER GREAT LAKES...

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

WATER VAPOR IMAGERY DEPICTED A BROAD CYCLONIC CIRCULATION CENTERED
OVER CENTRAL KENTUCKY WITH A SIGNIFICANT AMOUNT OF MID/UPPER-LEVEL
DRY AIR MOVING UP THE APPALACHIAN CHAIN. THIS SYSTEM WILL CONTINUE
TO BE THE FOCUS FOR WIDESPREAD CONVECTION BOTH UNDERNEATH THE
UPPER LOW ITSELF AS WELL AS FARTHER EAST WITHIN A VERY
MOIST/UNSTABLE ENVIRONMENT. DURING THE NEXT 36 HOURS...THE
GUIDANCE SHOWS THE SYSTEM MEANDERING ABOUT THE STATE OF KY BEFORE
A MORE NORTHWARD PUSH IS EVIDENT BY SATURDAY. WHILE DIFFERENCES
ARE NOT TREMENDOUS BY ANY MEANS...THE 12Z NAM/00Z CMC DO MOVE OFF
TOWARD THE SOUTH AND WEST OF THE STRONGER CLUSTERING BY THE
WEEKEND...PARTICULARLY THE CMC. WILL LEAN TOWARD THE REMAINING
CONSENSUS GIVEN THEIR SIMILAR OUTPUT.


...WEAK PERTURBATION MOVING FROM THE GREAT SALT LAKE TO THE
NORTHERN PLAINS THROUGH FRIDAY...

PRELIMINARY PREFERENCE: A NON-00Z CMC MODEL CONSENSUS
FORECAST CONFIDENCE: ABOVE AVERAGE

A SHEARING MID-LEVEL PERTURBATION SHOULD CONTINUE TO LIFT
NORTHWARD ALONG THE WESTERN EXTENT OF AN UPPER RIDGE POSITIONED
OVER THE GREAT PLAINS. LIKE YESTERDAY...THE 00Z CMC WAS A BIT
SLOWER EJECTING THE WAVE TOWARD THE HIGH PLAINS. OTHERWISE...A
CONSENSUS OF OTHER SOLUTIONS IS REASONABLE.


...DEEP UPPER TROUGH/SURFACE FEATURES REACHING THE PACIFIC
NORTHWEST BY FRIDAY AFTERNOON...
...PROGRESSIVE SHORTWAVE QUICKLY LIFTING UP TOWARD NORTHERN
SASKATCHEWAN...

PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

AN ACTIVE SYNOPTIC PATTERN IS IN PLACE OVER THE EASTERN PACIFIC
WITH A PAIR OF SYSTEMS AFFECTING THE WEST COAST DURING THE NEXT
FEW DAYS. INITIALLY...A POSITIVELY-TILTED TROUGH OFF THE COAST OF
BRITISH COLUMBIA WILL DIP SOUTHWARD BEFORE ACCELERATING TOWARD THE
PACIFIC NORTHWEST. PRIMARY DIFFERENCES APPEAR ONCE THE SYSTEM
LIFTS INTO WESTERN/CENTRAL CANADA SO A GENERAL MODEL COMPROMISE IS
REASONABLE WHILE THE TROUGH LIFTS THROUGH THE NORTHWESTERN U.S.


...TRAILING UPPER LOW DIPPING DOWN INTO NORTHERN CA BY LATE IN THE
WEEKEND...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF
FORECAST CONFIDENCE: AVERAGE

ON THE WINGS OF THE INITIAL TROUGH ACCELERATING THROUGH THE
PACIFIC NORTHWEST WILL BE A CLOSED LOW WHICH SINKS DOWN THE
IMMEDIATE WEST COAST. THIS FEATURE SHOULD REACH NORTHERN CA BY
03/0000Z WITH A FEW NOTABLE DIFFERENCES. MOST OBVIOUS...THE 00Z
CMC WAS DECIDEDLY SLOWER WITH THE UPPER TROUGH STILL OFF THE CA
COAST WHILE THE 09Z SREF MEAN REMAINED A TAD AHEAD OF THE PACK.
GIVEN THE ENSEMBLE SPAGHETTI PLOT SHOWS LOW-END SPREAD WITH THE
REMAINING SOLUTIONS...WILL FAVOR A BLEND OF THE 12Z GFS/00Z ECMWF
WHICH ARE RIGHT IN THE CENTER.



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

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

RUBIN-OSTER

$$





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