Prognostic Meteorological Discussion
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000
FXUS02 KWBC 281804
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
203 PM EDT TUE MAR 28 2017

VALID 12Z FRI MAR 31 2017 - 12Z TUE APR 4 2017

...OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES...

THE MAJORITY OF THE MODELS AND ENSEMBLE MEANS ARE INDICATING A
PERSISTENT SPLIT FLOW PATTERN WITH A RIDGE ACROSS WESTERN CANADA
AND INTO ALASKA, AND LARGE SCALE TROUGHING ACROSS THE WESTERN U.S.
 THE MODELS ARE IN OVERALL DECENT AGREEMENT THROUGH DAY 4 ON THE
OVERALL MID-LEVEL PATTERN AND HANDLE THE EVOLUTION OF THE UPPER
LOW OVER THE FOUR CORNER REGION.  ALTHOUGH THERE ARE SIMILARITIES
IN THE LONGWAVE PATTERN, THE OPERATIONAL MODELS AND ENSEMBLES
CONTINUE TO SHOW SIGNIFICANT MESOSCALE DIFFERENCES BEGINNING ON
DAY 5 OWING TO MODEL DIFFERENCES ORIGINATING FROM THE EASTERN
PACIFIC.

IN TERMS OF MODEL PERFORMANCE, THE 00Z CMC IS INITIALLY DEEPER
WITH THE TROUGH OVER THE EASTERN U.S. WHILE THE MODEL CONSENSUS IS
FLATTER WITH THIS WAVE.  BY SUNDAY MORNING, THE 12Z ECMWF BECOMES
MORE PROGRESSIVE WITH THE UPPER LOW EXITING NEW MEXICO, AND IS
WELL AHEAD OF THE MODEL CONSENSUS BY MONDAY EVENING OVER
TENNESSEE.  THE BIGGEST DIFFERENCES DURING THIS FORECAST PERIOD
ARE ACROSS THE WESTERN U.S. AS THE NEXT TROUGH BUILDS IN.  THE
ECMWF IS MUCH FARTHER EAST WITH THE TROUGH AXIS AND DIFFERS
SIGNIFICANTLY FROM THE EC MEAN.  GIVEN THE OVERALL PATTERN, THE
EVOLUTION FROM THE GFS IS CLOSER TO THE MEANS AND INDICATES
ANOTHER UPPER LOW DEVELOPING OVER THE FOUR CORNERS REGION BY
MONDAY NIGHT.  GIVEN THIS REASONING, THE EXTENDED FORECAST HEDGED
MORE TOWARD THE GFS/GEFS MEAN THAN THE ECWMF/EC MEAN.


...SENSIBLE WEATHER HIGHLIGHTS/POTENTIAL HAZARDS...

THE PART OF THE U.S WITH THE GREATEST WEATHER IMPACTS DURING THIS
TIME SHOULD ONCE AGAIN BE TEXAS AND THE LOWER MISSISSIPPI RIVER
VALLEY, AND THE FRONT RANGE OF THE ROCKY MOUNTAINS.  THE UPPER
LEVEL LOW AND THE RESULTING OCCLUDED SURFACE LOW ARE FORECAST TO
TRACK SLOWLY EASTWARD AND PERHAPS BE CLOSE TO A REPEAT OF THE
ONGOING STORM SYSTEM CURRENTLY OVER THE SOUTH-CENTRAL PART OF THE
NATION.  THE STORM PREDICTION CENTER IS INDICATING FAVORABLE
CONDITIONS FOR ADDITIONAL SEVERE WEATHER OVER THE UPCOMING WEEKEND
ACROSS THE SOUTHERN PLAINS.  VERY HEAVY RAINFALL CAPABLE OF
PRODUCING FLASH FLOODING WILL BE POSSIBLE AS WELL AHEAD OF THE LOW
ACROSS SOUTHERN TEXAS AND LOUISIANA.  BASED ON THE LATEST MODEL
GUIDANCE, THIS SYSTEM SHOULD TAKE A MORE SOUTHERLY TRACK THAN THE
CURRENT ONE.  HEAVY SNOW IS ALSO EXPECTED FOR THE COLORADO ROCKIES
WITH STRONG UPSLOPE FLOW ON THE NORTH SIDE OF THIS LOW.

EXPECT TEMPERATURES TO BE ABOVE NORMAL ACROSS THE MAJORITY OF THE
NATION DURING THIS TIME PERIOD, WITH THE GREATEST ANOMALIES
EXPECTED ACROSS THE NORTHERN PLAINS AND EXTENDING TO THE OHIO
VALLEY.  ANOTHER AREA WITH NOTEWORTHY WARM TEMPERATURES WILL BE
FROM SOUTHERN TEXAS TO THE SOUTHEAST U.S., WITH WIDESPREAD HIGHS
IN THE 80S LIKELY AND NOTICEABLE LEVELS OF HUMIDITY.  COLDER THAN
NORMAL READINGS ARE LIKELY NEAR THE SOUTHWESTERN UPPER LOW THAT
TRACKS TOWARDS THE SOUTHERN PLAINS BY SATURDAY, AND ALSO FOR NEW
ENGLAND AT THE BEGINNING OF THE PERIOD.

HAMRICK

$$





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