695  
FXUS02 KWBC 041935  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
335 PM EDT THU APR 04 2019  
 
VALID 12Z SUN APR 07 2019 - 12Z THU APR 11 2019  
   
..OVERVIEW
 
 
AN ONGOING PROGRESSION OF PACIFIC SYSTEMS INTO AND ACROSS THE  
LOWER 48 WILL BRING ACTIVE WEATHER TO A DECENT PERCENTAGE OF THE  
COUNTRY. THE SOUTHWESTERN U.S./SOUTHERN ROCKIES APPEAR TO BE THE  
ONE AREA THAT SHOULD HAVE FAIRLY DRY WEATHER. A LEADING UPPER  
TROUGH OVER THE CENTRAL U.S. SUN AND ITS ASSOCIATED SURFACE SYSTEM  
WILL SPREAD A BROAD AREA OF PRECIPITATION ACROSS THE EASTERN HALF  
OF THE COUNTRY SUN-TUE WITH SOME AREAS OF HEAVY RAINFALL POSSIBLE.  
DURING THAT SAME TIME FRAME EXPECT A STRONG JET AIMED AT THE  
NORTHWESTERN STATES TO BRING AREAS OF ENHANCED PRECIPITATION TO  
THE NORTHERN HALF OF THE WEST COAST INLAND TO THE NORTHERN  
ROCKIES. A DYNAMIC UPPER TROUGH FORECAST TO CREST THE WEST COAST  
BY TUE WILL CONTINUE INLAND TO PUSH A MAIN PRECIPITATION FOCUS  
EASTWARD TO THE NORTH-CENTRAL ROCKIES THEN NORTH-CENTRAL  
PLAINS/MISSISSIPPI VALLEY AND EVENTUALLY THE OHIO VALLEY AND GREAT  
LAKES. THERE IS AN INCREASING GUIDANCE SIGNAL THAT THIS POTENT  
TROUGH MAY SUPPORT STRONG CENTRAL U.S. STORM GENESIS WED-THU. THIS  
PRESENTS A RISK OF WRAPPING ENHANCED SNOWS FROM THE ROCKIES TO THE  
NORTH-CENTRAL PLAINS/UPPER MIDWEST, ALBEIT WITH MARGINALLY COLD  
AIR. OVER THE SOUTH-CENTRAL U.S., GUIDANCE MAY BE UNDERESTIMATING  
AN ADDITIONAL THREAT OF STRONG TO SEVERE THUNDERSTORMS ALONG A  
TRAILING COLD FRONT. MEANWHILE UPSTREAM, UPPER LEVEL TROUGH ENERGY  
REACHING THE NORTHEASTERN PACIFIC MAY ALSO APPROACH THE WEST COAST  
WITH SOME UNSETTLED WEATHER AROUND NEXT THU.  
 
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A  
COMPOSITE BLEND OF THE 00 UTC GFS/ECMWF AND GEFS/ECMWF ENSEMBLE  
MEANS. THESE GUIDANCE OPTIONS SEEM FAIRLY WELL CLUSTERED WITH THE  
FORECAST EVOLUTION OF MID-LARGER SCALE SYSTEMS. A COMPOSITE BLEND  
MITIGATES RECENT ISSUES WITH GUIDANCE TO MAINTAIN ACCEPTABLE  
CONTINUITY WITH THE EMBEDDED SMALLER SCALE SYSTEMS AND STREAM  
INTERACTIONS.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
STRONG FLOW ALOFT ACROSS THE NORTHWEST WILL PROMOTE AREAS OF  
TERRAIN-ENHANCED RAIN AND HIGHER ELEVATION SNOW FROM NORTHERN  
CALIFORNIA AND THE PACIFIC NORTHWEST INTO NORTHERN ROCKIES FROM  
SUN INTO EARLY NEXT WEEK. CURRENT GUIDANCE SUGGESTS BEST POTENTIAL  
FOR HEAVIEST ACTIVITY WILL BE CENTERED ALONG THE WEST COAST NEAR  
THE CALIFORNIA/OREGON BORDER AND THE OREGON CASCADES. BY TUE THE  
UPPER TROUGHING MOVING INTO THE WEST WILL BEGIN TO SHIFT THE BEST  
MOISTURE FOCUS EASTWARD INTO THE GREAT BASIN AND NORTHERN-CENTRAL  
ROCKIES. CONTINUED PROGRESSION OF THIS SYSTEM SHOULD SPREAD  
PRECIPITATION ACROSS THE NORTH-CENTRAL PLAINS, MID-UPPER  
MISSISSIPPI VALLEY, AND EVENTUALLY OHIO VALLEY AND GREAT LAKES BY  
WED-THU. SOME ACTIVITY MAY BE HEAVY AND AREAS WITH ONGOING  
FLOODING CONCERNS WILL NEED TO MONITOR THIS SYSTEM. A PERIOD OF  
LOW LEVEL UPSLOPE FLOW MAY ADD TO TOTALS OVER THE  
EASTWARD/NORTHWARD FACING SLOPES OF THE ROCKIES. IN ADDITION  
STRONGER TRENDS FOR WED-THU LOW PRESSURE IN LATEST GUIDANCE RAISE  
THE POTENTIAL FOR STRONG WINDS TO BE AN ISSUE OVER SOME AREAS.  
THERE IS ALSO A THREAT OF SNOW IN THE NORTHERN PERIPHERY OF THE  
WRAPBACK PRECIP SHIELD FROM THE N-CENTRAL PLAINS TO THE UPPER  
MIDWEST.  
 
THE EASTERN HALF OF THE COUNTRY WILL SEE A BROAD AREA OF  
PRECIPITATION WITH THE SYSTEM PROGRESSING EASTWARD FROM THE PLAINS  
SUN ONWARD. AMPLE FLOW OF MOISTURE FROM THE GULF WILL PROMOTE  
AREAS OF HEAVY RAINFALL. BEST POTENTIAL FOR HIGHEST TOTALS WILL BE  
OVER/NEAR THE LOWER MISSISSIPPI VALLEY AND CENTRAL GULF COAST  
REGION AND SOUTHERN APPALACHIANS. CONVECTION MAY BE STRONG TO  
SEVERE OVER SOUTHERN AREAS. CHECK SPC OUTLOOKS AS SPECIFICS BECOME  
BETTER RESOLVED OVER THE COMING DAYS. SIGNIFICANT RAINFALL IS ALSO  
POSSIBLE FROM THE OHIO VALLEY INTO NORTHERN  
MID-ATLANTIC/NORTHEAST. THERE ARE STILL SIGNIFICANT DETAIL  
UNCERTAINTIES WITH THIS SYSTEM SO CONFIDENCE IN LOCATION/MAGNITUDE  
OF HEAVIEST RAINFALL REMAINS SOMEWHAT LOWER THAN DESIRED. SNOW  
SHOULD BE CONFINED MOSTLY TO NORTHERN NEW ENGLAND MON-WED IN THIS  
PATTERN AS MOISTURE ADVECTS NORTHWARD INTO A COOLED/RECEDING  
SURFACE RIDGE.  
 
THE WARM SECTOR OF THE CENTRAL-EASTERN U.S. SYSTEM SUN/MON WILL  
OFFER SOME MUCH ABOVE NORMAL TEMPERATURES. MORNING LOWS WILL BE  
PARTICULARLY ANOMALOUS WITH MANY LOCATIONS 15-25F ABOVE NORMAL SUN  
INTO TUE AND SOME DAILY RECORD WARM LOW VALUES MAY BE CHALLENGED.  
THE MAIN UPSTREAM SYSTEM WILL THEN SPREAD A PERIOD OF ANOMALOUS  
WARMTH ACROSS THE SOUTHWEST THEN SOUTHERN PLAINS AND  
SOUTH-SOUTHEAST U.S. NEXT WEEK.  
 
SCHICHTEL  
 
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 THE HIGHER TERRAIN OF CALIFORNIA,  
OREGON, AND WASHINGTON, SUN-MON, APR 7-APR 8.  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE NORTHERN ROCKIES AND  
THE NORTHERN GREAT BASIN, SUN-TUE, APR 7-APR 9.  
- HEAVY PRECIPITATION FROM PORTIONS OF THE CENTRAL ROCKIES TO THE  
UPPER MIDWEST, TUE-THU, APR 9-APR 11.  
- HEAVY RAIN ACROSS PORTIONS OF CALIFORNIA AND THE PACIFIC  
NORTHWEST, SUN-MON, APR 7-APR 8.  
- HEAVY RAIN ACROSS PORTIONS OF THE LOWER TO MIDDLE MISSISSIPPI  
VALLEY, SUN, APR 7.  
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHERN APPALACHIANS, MON,  
APR 8.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN PLAINS AND THE  
NORTHERN GREAT BASIN.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE  
MISSISSIPPI AND MISSOURI RIVER BASINS.  
- FLOODING LIKELY ACROSS PORTIONS OF THE UPPER MISSISSIPPI VALLEY  
AND THE NORTHERN PLAINS.  
- HIGH WINDS ACROSS PORTIONS OF THE SOUTHWEST AND THE CENTRAL AND  
SOUTHERN HIGH PLAINS, TUE-THU, APR 9-APR 11.  
- HIGH SIGNIFICANT WAVE HEIGHTS FOR COASTAL PORTIONS OF THE  
PACIFIC NORTHWEST, SUN, APR 7.  
 
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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