399  
FXUS02 KWBC 011601  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1200 PM EDT MON APR 01 2019  
 
VALID 12Z THU APR 04 2019 - 12Z MON APR 08 2019  
   
..OVERVIEW
 
 
THIS PERIOD WILL FEATURE A STEADY PROGRESSION OF PACIFIC FEATURES  
INTO THE WEST THAT CONTINUE ONWARD TO PRODUCE SEVERAL EPISODES OF  
ACTIVE WEATHER OVER THE EAST-CENTRAL U.S. HEAVIEST PRECIPITATION  
SHOULD EXTEND FROM THE CENTRAL/NORTHERN WEST COAST TO THE NORTHERN  
ROCKIES AS WELL AS DOWNSTREAM FROM THE SOUTHERN PLAINS/SOUTH TO  
THE APPALACHIANS/MID-ATLANTIC.  
 
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
LATEST MODELS AND ENSEMBLES REMAIN REMARKABLY STUBBORN IN  
MAINTAINING THEIR SPREAD FOR SHORTWAVE ENERGY ALOFT AND ASSOCIATED  
SURFACE LOWS TRACKING ACROSS THE EASTERN HALF OF THE COUNTRY LATE  
THIS WEEK INTO THE START OF THE WEEKEND. AS HAS BEEN THE CASE IN  
RECENT DAYS THERE IS DECENT CLUSTERING FOR LOW PRESSURE OVER THE  
SOUTH-CENTRAL PLAINS EARLY THU. THEN INDIVIDUAL MODELS/ENSEMBLE  
MEMBERS RAPIDLY DIVERGE FOR THE LATITUDE OF BEST-DEFINED LOW  
CENTERS FARTHER EAST. IN FORECASTS VALID EARLY FRI THE ONE TREND  
OF NOTE IS A REDUCTION OF ENSEMBLE MEMBERS IN THE NORTHERN PART OF  
THE SPREAD IN THE GREAT LAKES. ON THE OTHER HAND RECENT ECMWF/CMC  
RUNS REMAIN ON THE SOUTHERN PART OF THE SPREAD. BY EARLY SAT THERE  
IS STILL THE POTENTIAL FOR LOW PRESSURE CENTERS ANYWHERE FROM  
NORTHERN NEW ENGLAND TO SOUTHERN COASTAL MID-ATLANTIC. CONFIDENCE  
REMAINS LOW FOR SYSTEM SPECIFICS DUE TO THE SENSITIVITY TO SMALL  
SCALE DETAILS ALOFT THAT INCLUDE A COMBINATION OF INITIAL PLAINS  
SHORTWAVE AND NORTHERN TIER ENERGY THAT COULD INTERACT BY FRI. WPC  
PROGS NOW FAVOR A WEAKENING NORTHERN STREAM SURFACE WAVE TRACKING  
THROUGH THE OHIO VALLEY AND NORTHEAST AS A SOUTHERN STREAM SURFACE  
WAVE FOCUSES POTENTIAL FOR DEEPER MOISTURE/RAINFALL/CONVECTION  
UNDERNEATH OVER THE SOUTH AND MID-ATLANTIC.  
 
UPSTREAM, A FAIRLY STRONG NORTHEASTERN PACIFIC STORM SHOULD BRING  
A DECENT FRONT (WITH VIGOROUS UPPER SHORTWAVE SUPPORT) INTO THE  
WEST BY SAT, POTENTIALLY FOLLOWED A DAY LATER BY ANOTHER SYSTEM  
TRACKING NEAR VANCOUVER ISLAND AND BRINGING A FRONT/ENERGY ALOFT  
TO THE NORTHWEST. GUIDANCE HAS BEEN FAIRLY CONSISTENT IN WEAKENING  
SHORTWAVE ENERGY THAT CROSSES THE NORTHWEST AND HEADS INTO A  
DOWNSTREAM RIDGE, WHILE SOUTHERN STREAM SHORTWAVES CROSS THE  
SOUTHWEST U.S./NORTHERN MEXICO AND THEN SOUTHERN  
PLAINS/MISSISSIPPI VALLEY BY THE WEEKEND.  
THERE IS STILL A RAPID INCREASE IN FORECAST SPREAD FOR DETAILS OF  
FLOW ALOFT FROM THE PACIFIC INTO THE WESTERN U.S., BUT RELATIVE  
AGREEMENT AMONG THE ENSEMBLE MEANS.  
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
ASIDE FROM THE TYPICALLY VARIABLE FINER DETAILS, THERE IS GOOD  
CONTINUITY IN THE FORECAST OF MULTIPLE PERIODS OF SIGNIFICANT  
RAINFALL/HIGHER ELEVATION SNOW FROM NORTHERN CALIFORNIA/SIERRA  
NEVADA AND PACIFIC NORTHWEST INTO THE NORTHERN ROCKIES. HIGHEST  
FIVE-DAY TOTALS WILL LIKELY BE OVER FAVORED TERRAIN IN THE WEST  
COAST STATES WITH SOMEWHAT LESS MOISTURE REACHING THE ROCKIES.  
HEAVIEST PRECIPITATION SHOULD OCCUR ALONG THE WEST COAST DURING  
FRI-SUN. MEANWHILE THE SYSTEM TRACKING OUT OF THE PLAINS THU  
ONWARD WILL SPREAD A DECENT MOISTURE SHIELD ACROSS THE EASTERN  
HALF OF THE COUNTRY, BUT WITH CONTINUED LACK OF CONFIDENCE IN  
SPECIFICS. TODAY THERE IS SOMEWHAT MORE OF A SIGNAL FOR HEAVY  
RAINFALL POTENTIAL OVER THE LOWER MISSISSIPPI/TENNESSEE  
VALLEY/GULF COAST REGION, AND SOME CONVECTION OVER THIS AREA COULD  
BE STRONG TO SEVERE. CHECK SPC OUTLOOKS FOR LATEST INFO ON SEVERE  
THREATS. SOME SNOW MAY BE POSSIBLE INTO THE NORTHERN GREAT  
LAKES/NEW ENGLAND. BEHIND THIS SYSTEM, MOST GUIDANCE CONTINUES TO  
SUGGEST A HEAVY RAINFALL THREAT NEXT WEEKEND/MONDAY FOR THE  
SOUTHERN PLAINS/LOWER MISSISSIPPI VALLEY. THIS ACTIVITY WILL BE  
ENCOURAGED BY THE APPROACHING SOUTHERN STREAM SHORTWAVE ALOFT AND  
A HEALTHY FLOW OF GULF MOISTURE INTERACTING WITH A STALLED FRONT  
THAT SHOULD RETURN NORTH AS A WARM FRONT. RAINFALL OF VARYING  
INTENSITY SHOULD ALSO SPREAD FARTHER NORTHWARD ACROSS THE CENTRAL  
AND EVENTUALLY EASTERN U.S.  
 
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  
 
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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