949  
FXUS02 KWBC 020700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT TUE APR 02 2019  
 
VALID 12Z FRI APR 05 2019 - 12Z TUE APR 09 2019  
   
..OVERVIEW
 
 
EXPECT CONTINUED MODERATE PROGRESSION OF PACIFIC FLOW INTO/ACROSS  
THE LOWER 48 DURING THE PERIOD. THIS PATTERN SHOULD BRING  
MULTIPLE EPISODES OF PRECIPITATION TO AREAS FROM THE  
NORTHERN-CENTRAL WEST COAST INTO THE NORTHERN ROCKIES, WHILE THE  
EASTERN HALF OF THE COUNTRY WILL LIKELY SEE TWO BROAD AREAS OF  
MOISTURE--ONE WITH A FAIRLY WEAK LEADING SYSTEM CROSSING THE EAST  
AND ANOTHER WITH A SYSTEM TRACKING FROM THE SOUTHERN PLAINS  
NORTHEASTWARD DURING THE WEEKEND AND EARLY NEXT WEEK. TO THE EAST  
OF THE ROCKIES, BEST POTENTIAL FOR HIGHEST RAINFALL TOTALS SHOULD  
BE WITHIN AN AREA EXTENDING FROM TEXAS THROUGH THE LOWER  
MISSISSIPPI VALLEY INTO THE SOUTHEAST/SOUTHERN APPALACHIANS. SOME  
AREAS FARTHER NORTH COULD SEE SIGNIFICANT RAINFALL AS WELL.  
 
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
DURING THE FIRST COUPLE DAYS OR SO OF THE PERIOD A  
MULTI-MODEL/MULTI-RUN CONSENSUS (PAST TWO 12-HOURLY ECMWF RUNS AND  
6-HOURLY GFS RUNS THROUGH THE 12-18Z CYCLES, WITH SOME 12Z CMC  
INCLUDED) REPRESENTED THE MOST LIKELY SOLUTION ACROSS THE LOWER 48  
AND VICINITY. GUIDANCE AGREES IN PRINCIPLE ON INDIVIDUAL FEATURES  
BUT SHOWS TYPICAL DIFFERENCES FOR SMALLER DETAILS THAT HAVE LOW  
PREDICTABILITY. THE SYSTEM INITIALLY OVER THE EAST AS OF FRI  
STILL LOOKS DIFFUSE ALOFT AND AS A RESULT MODELS ARE HAVING  
TROUBLE RESOLVING SURFACE SPECIFICS. LONG-TERM TREND HAS BEEN  
TOWARD A WEAKER SURFACE REFLECTION WHICH WAS ADVERTISED EARLIER BY  
ECMWF-BASED GUIDANCE. THERE IS STILL A LOT OF SPREAD THOUGH.  
MEANWHILE A STRONG STORM TO THE WEST/NORTHWEST OF THE PACIFIC  
NORTHWEST WILL BRING A FRONT INTO THE WEST FRI-SAT AND INTO THE  
PLAINS BY SUN. TRAILING BURSTS OF ENERGY ALOFT/SURFACE FEATURES  
SHOULD CONTINUE INTO THE NORTHWEST THROUGH THE WEEKEND. THE 12Z  
UKMET SEEMED TO DIFFER THE GREATEST FROM OTHER SOLUTIONS FOR  
DETAILS OVER THE EASTERN PACIFIC/NORTHWEST U.S. AND THUS WAS  
EXCLUDED FROM THE BLEND. LEADING SHORTWAVE ENERGY OVER THE WEST  
LATE THIS WEEK WILL FOCUS IN THE SOUTHERN STREAM AS IT HEADS EAST,  
REACHING THE SOUTHERN PLAINS BY SAT.  
 
BY THE LATTER HALF OF THE PERIOD THERE ARE TWO PROMINENT OVERALL  
UNCERTAINTIES: 1. HOW ENERGY REACHING THE WEST ON SAT ULTIMATELY  
EVOLVES AND INTERACTS WITH LEADING SOUTHERN STREAM SHORTWAVE  
ENERGY OVER THE PLAINS--AFFECTING THE FORECAST OVER THE EASTERN  
HALF OF THE COUNTRY, 2. THE STRENGTH OF RIDGING THAT BUILDS INTO  
THE WEST BY SUN-TUE AND RESULTING SPEED OF AN UPSTREAM EASTERN  
PACIFIC TROUGH. FOR THIS LATTER WESTERN ISSUE, THE MAJORITY OF  
GUIDANCE SHOWS LESS PRONOUNCED WESTERN RIDGING AND FASTER PACIFIC  
TROUGH VERSUS THE GFS/GEFS RUNS FROM THE PAST COUPLE DAY. A  
POSITIVE HEIGHT ANOMALY CENTER TO THE EAST OF GREENLAND AND A  
NEGATIVE HEIGHT ANOMALY CENTER OVER THE WEST-CENTRAL PACIFIC IN  
RECENT D+8 CHARTS TELECONNECT TO A SPLIT-FLOW PATTERN OVER WESTERN  
NORTH AMERICA (MEAN RIDGING GENERALLY CONFINED TO CANADA AND  
NORTHERN PARTS OF THE WESTERN U.S.). THIS SEEMS TO FAVOR AN  
EVOLUTION CLOSER TO THE ECMWF/CMC AND THEIR MEANS, AT LEAST IN  
TERMS OF HAVING LOWER HEIGHTS THAN THE GFS/GEFS OVER SOUTHERN  
PARTS OF THE WEST. FARTHER EAST GFS RUNS VARY FROM  
CONSENSUS/MEANS IN VARYING WAYS, THE 18Z GFS STRAYING ON THE FAST  
SIDE AND THE NEW 00Z RUN BECOMING MUCH STRONGER WITH NORTHERN TIER  
ENERGY ALOFT. HOWEVER CONFIDENCE IN OTHER MODEL DETAILS IS NOT  
GREAT EITHER. THESE CONSIDERATIONS FAVOR TRENDING THE FORECAST  
TOWARD A BLEND OF RECENT ECMWF RUNS, 12Z CMC, AND 12Z NAEFS/ECMWF  
MEANS. THE NAEFS PROVIDES A MODEST HEDGE TO ACCOUNT FOR THE  
POSSIBILITY OF SLIGHTLY SLOWER PACIFIC/WESTERN U.S. PROGRESSION.  
 
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
CONTINUE TO EXPECT PERIODS OF ENHANCED RAINFALL/HIGHER ELEVATION  
SNOW FROM THE CENTRAL/NORTHERN WEST COAST INTO THE NORTHERN  
ROCKIES. SOME LOCATIONS ALONG THE MOST FAVORED TERRAIN FROM  
NORTHERN CALIFORNIA/SIERRA NEVADA INTO WESTERN WASHINGTON/OREGON  
MAY SEE AT LEAST SEVERAL INCHES LIQUID OVER THE FRI-TUE PERIOD.  
THE NORTHERN ROCKIES SHOULD SEE LESSER BUT STILL SIGNIFICANT  
TOTALS. INDIVIDUAL SYSTEMS AFFECTING THE PACIFIC NORTHWEST COAST  
MAY ALSO BE ACCOMPANIED BY PERIODS OF STRONG WINDS. CONFIDENCE IN  
PRECIPITATION COVERAGE AND INTENSITY DECREASES DURING THE FIRST  
HALF OF NEXT WEEK AS GUIDANCE DIVERGES FOR AMPLITUDE/TIMING OF  
SIGNIFICANT FEATURES.  
 
LEADING AREA OF PRECIPITATION OVER THE EAST, POSSIBLY INCLUDING  
SOME SNOW OVER NEW ENGLAND, SHOULD DEPART AFTER FRI NIGHT. SOME  
POCKETS OF LOCALLY HEAVIER PRECIPITATION ARE POSSIBLE BUT THERE IS  
NOT A CLEAR SIGNAL FOR WHERE SUCH ACTIVITY MAY OCCUR. FROM FRI  
NIGHT ONWARD THE SHORTWAVE ALOFT APPROACHING/REACHING THE SOUTHERN  
PLAINS ALONG WITH STRENGTHENING FLOW OF GULF MOISTURE INTERACTING  
WITH A STALLED FRONT WILL LIKELY LEAD TO A HEAVY RAINFALL THREAT  
OVER THE SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY AND POSSIBLY  
EXTENDING TO THE EAST/NORTHEAST. LOW PRESSURE TRACKING  
NORTHEASTWARD FROM THE SOUTHERN PLAINS SHOULD EVENTUALLY HELP TO  
SPREAD MOISTURE OVER MUCH OF THE EASTERN HALF OF THE COUNTRY.  
DEPENDING ON HOW THIS SYSTEM EVOLVES THERE MAY BE SOME BANDS OF  
SIGNIFICANT RAINFALL IN MIDDLE/NORTHERN LATITUDES BETWEEN THE  
PLAINS AND EAST COAST. PLAINS/MISSISSIPPI VALLEY AREAS SENSITIVE  
TO ADDITIONAL RAINFALL SHOULD MONITOR FORECASTS FOR THIS SYSTEM.  
 
THE OVERALL PATTERN SHOULD FAVOR MODESTLY BELOW NORMAL HIGHS OVER  
THE WEST COAST STATES INTO THE NORTHERN ROCKIES BUT WITH A WARMING  
TREND OVER SOUTHERN AREAS. LOWS SHOULD BE ABOVE NORMAL THROUGH  
THE PERIOD (SOME PLUS 10-15F ANOMALIES). MOST AREAS EAST OF THE  
ROCKIES SHOULD SEE ABOVE TO MUCH ABOVE NORMAL TEMPERATURES, THOUGH  
WITH A COOLING TREND BEHIND THE FRONT REACHING THE EASTERN STATES  
LATE IN THE PERIOD. MORNING LOWS MAY BE 15-25F ABOVE NORMAL OVER  
PARTS OF THE NORTHERN PLAINS AND MIDWEST AROUND SUN-MON WITH SOME  
DAILY RECORD WARM LOW VALUES POSSIBLE.  
 
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  
 
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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