978  
FXUS02 KWBC 292005  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
404 PM EDT FRI MAR 29 2019  
 
VALID 12Z MON APR 01 2019 - 12Z FRI APR 05 2019  
 
...NOR'EASTER LIKELY FOR MIDWEEK, BUT WITH A LARGE TIMING  
DISCREPANCY...  
 
   
..OVERVIEW
 
 
STRONG UPPER RIDGING OVER ALASKA WILL SLOWLY MIGRATE INTO  
NORTHEASTERN RUSSIA, FAVORING NORTHERN STREAM TROUGHING ACROSS  
MUCH OF CANADA AND INITIALLY OVER THE EASTERN CONUS BUT THEN  
ACROSS THE CENTRAL CONUS LATE NEXT WEEK. WITH THE BLOCK IN THE  
NORTHEASTERN PACIFIC, SOUTHERN STREAM SYSTEMS WILL MOVE THROUGH  
THE GREAT BASIN/FOUR CORNERS REGION AND ACROSS THE MID-MISSISSIPPI  
AND TENNESSEE VALLEYS. THIS SUPPORTS A LEAD EAST COAST NOR'EASTER  
(STILL ENCUMBERED IN UNCERTAINTY) AT THE SAME TIME AS A WESTERN  
SYSTEM MOVES INTO THE PLAINS.  
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
WITHIN THE FAIRLY AGREEABLE MEAN PATTERN THERE ARE SOME  
SIGNIFICANT ISSUES WITH SPECIFICS. DIFFERENCES IN HANDLING THE  
INITIAL ALASKA RIDGE PLAY AT LEAST A PARTIAL ROLE IN THE  
DIVERGENCE OF SOLUTIONS FOR FLOW ACROSS SOUTHERN CANADA AND  
NORTHERN U.S. AT QUESTION IS THE SHAPE/STRENGTH OF THE NORTHERN  
STREAM AND ITS INTERACTION WITH A SHORTWAVE MOVING THROUGH THE  
SOUTHEAST ON TUESDAY. THIS FEATURE HAS HAD POOR CONTINUITY BACK  
SEVERAL DAYS AND, COUPLED WITH UNCERTAINTY IN THE NORTHERN STREAM,  
HAS LED TO HIGH UNCERTAINTY. ONGOING WPC FORECAST HAS ALWAYS HAD  
THIS COASTAL SYSTEM LYING JUST OFF THE COAST AFTER ORGANIZING EAST  
OF GA/FL BUT IT WAS UNCLEAR IF IT WOULD LIFT NORTHEASTWARD CLOSE  
TO THE NEW ENGLAND COAST OR ONLY SLOWLY SAUNTER EAST-NORTHEASTWARD  
TOWARD BERMUDA IF THE NORTHERN STREAM TROUGH PASSED BY TO ITS  
NORTHEAST. TREND IN THE ENSEMBLE GUIDANCE FAVORS A CLOSER/COASTAL  
TRACK THOUGH THE 00Z UKMET/CANADIAN WERE NOTABLE EXCEPTIONS ON THE  
FAR SOUTHERN SIDE OF THE ENVELOPE OF SOLUTIONS. IN ADDITION, THE  
QUICKER SPEED TIED TO THE NORTHERN STREAM MAY ALLOW TO SYSTEM TO  
RACE NORTHEASTWARD MUCH QUICKER THAN PREVIOUSLY FORECAST, BUT DID  
NOT JUMP TO THE QUICKEST SOLUTIONS (00Z ECMWF/ECMWF ENSEMBLE MEAN  
AND 06Z FV3-GFS) GIVEN THE SPREAD/CONTINUITY. AS SUCH, THE 00Z/06Z  
GFS REPRESENTED A BEST INTERMEDIATE SOLUTION FOR NOW WITH THE  
SYSTEM.  
 
LOOKING FARTHER WESTWARD, MOST SOLUTIONS EXPECT ENERGY OFFSHORE  
BRITISH COLUMBIA TO PROGRESS THROUGH THE WEST AROUND TUE-WED AND  
THE PLAINS/MISSISSIPPI VALLEY THU-FRI. AT THE SURFACE LOW PRESSURE  
WILL LIKELY TRACK INTO THE NORTHWEST EARLY IN THE WEEK AND THEN A  
WAVY FRONTAL SYSTEM SHOULD REACH THE CENTRAL STATES AROUND  
THURSDAY. WITH CONTINUED DIFFERENCES IN THE DETERMINISTIC MODELS  
AT THE SURFACE AND ALOFT BY THE LATTER HALF OF THE PERIOD, FAVORED  
GREATER EMPHASIS ON THE ENSEMBLE MEANS AT THAT TIME.  
 
IN THE WAKE OF THIS SYSTEM EXPECT A MODEST RIDGE TO BUILD INTO THE  
WEST COAST/INTERIOR WEST WHILE MORE TROUGH ENERGY PUSHES INTO THE  
EASTERN PACIFIC. THE ENSEMBLE MEANS WERE FAIRLY CLOSE AND MERITED  
THE GREATEST WEIGHT IN THE FORECAST BY LATE IN THE PERIOD.  
 
...WEATHER HIGHLIGHTS/HAZARDS  
 
EXPECT RAIN/HIGHER ELEVATION SNOW TO SPREAD THROUGH THE NORTHERN  
HALF TO TWO-THIRDS OF THE WEST IN THE MON-WED PERIOD, FOLLOWED BY  
ADDITIONAL PRECIPITATION REACHING THE WEST COAST LATE IN THE WEEK.  
HIGHEST PRECIPITATION TOTALS ARE MOST LIKELY OVER NORTHERN  
CALIFORNIA/SIERRA NEVADA WITH ENHANCED ACTIVITY REACHING INTO THE  
NORTHERN/CENTRAL ROCKIES. LOCATIONS ACROSS THE SOUTH AND EAST  
COAST REGIONS MAY SEE A PERIOD OF RAIN (AND QUITE POSSIBLY SOME  
SNOW OVER HIGHER ELEVATIONS) WITH THE SYSTEM FORECAST TO TRACK  
JUST OFF THE EAST COAST. WIDE GUIDANCE SPREAD FOR TRACK AND TIMING  
KEEPS CONFIDENCE LOW WITH RESPECT TO PRECIPITATION TYPE, COVERAGE,  
INTENSITY, AND TIMING. POCKETS OF LOCALLY MODERATE/HEAVY RAINFALL  
MAY BE POSSIBLE AND PERHAPS SNOWFALL ALONG AND EAST OF THE  
APPALACHIAN CREST. GIVEN THAT IT WILL BE EARLY APRIL, TEMPERATURES  
WILL BE MARGINAL AND TIME OF DAY OF PRECIPITATION WILL INFLUENCE  
ACTUAL ACCUMULATION. AREAS OF WESTERN NC, SOUTHWESTERN VA, AND  
EASTERN WV WERE HIGHLIGHTED IN THE DAY 4-7 WINTER WEATHER OUTLOOK  
PROBABILITIES AS WELL AS HIGHER TERRAIN OF THE NORTHEAST.  
 
THE SYSTEM EMERGING FROM THE WEST MAY SPREAD PRECIPITATION ALONG A  
WAVY FRONTAL SYSTEM INTO THE PLAINS/MISSISSIPPI VALLEY REGION  
DURING THE LATTER HALF OF THE WEEK. THUS FAR SIGNALS FOR  
SIGNIFICANT AMOUNTS ARE NOT AGREEABLE ENOUGH TO PROVIDE MEANINGFUL  
CONFIDENCE IN SPECIFICS. TEMPERATURES WILL VARY IN ACCORDANCE  
WITH SYSTEM PROGRESSION. THE SOUTH AND EAST WILL BE ON THE CHILLY  
SIDE EARLY IN THE WEEK WITH SOME AREAS OF MINUS 10-20F ANOMALIES  
IN THE WAKE OF THE COASTAL SYSTEM. THEN ABOVE NORMAL READINGS  
(MOSTLY PLUS 5-15F ANOMALIES) SHOULD PROGRESS FROM THE WEST AND  
INTO THE CENTRAL/EASTERN STATES OVER THE COURSE OF THE WEEK AS  
HEIGHTS REBOUND.  
 
FRACASSO/RAUSCH  
 
ADDITIONAL 3-7 DAY HAZARDS INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
HAZARDS:  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE PACIFIC NORTHWEST,  
MON-TUE, APR 1-APR 2.  
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST, THE MID-ATLANTIC,  
THE PACIFIC NORTHWEST, NORTHERN CALIFORNIA, AND THE NORTHERN GREAT  
BASIN, MON-TUE, APR 1-APR 2.  
- HEAVY RAIN ACROSS PORTIONS OF NORTHERN CALIFORNIA, SOUTHWESTERN  
OREGON, AND THE OLYMPIC MOUNTAINS, FRI, APR 5.  
- HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE CENTRAL  
GREAT BASIN, THE NORTHERN ROCKIES, THE NORTHERN GREAT BASIN, AND  
THE NORTHERN PLAINS, TUE-WED, APR 2-APR 3.  
- HEAVY SNOW ACROSS PORTIONS OF THE NORTHERN ROCKIES AND THE  
NORTHERN GREAT BASIN, TUE, APR 2.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE UPPER MISSISSIPPI  
VALLEY, THE MIDDLE MISSISSIPPI VALLEY, THE NORTHERN PLAINS, AND  
THE NORTHERN GREAT BASIN.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE CENTRAL  
PLAINS, THE LOWER MISSISSIPPI VALLEY, THE NORTHERN PLAINS, THE  
TENNESSEE VALLEY, THE MIDDLE MISSISSIPPI VALLEY, THE UPPER  
MISSISSIPPI VALLEY, THE GREAT LAKES, AND THE OHIO VALLEY.  
- FLOODING LIKELY ACROSS PORTIONS OF THE MIDDLE MISSISSIPPI VALLEY.  
- HIGH WINDS ACROSS PORTIONS OF THE NORTHEAST, WED, APR 3.  
- HIGH WINDS ACROSS PORTIONS OF THE MID-ATLANTIC, TUE-WED, APR  
2-APR 3.  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDICES ARE AT:  
 
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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