074  
FXUS02 KWBC 121901  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
259 PM EDT TUE APR 12 2022  
 
VALID 12Z FRI APR 15 2022 - 12Z TUE APR 19 2022  
 
   
..OVERVIEW
 
 
LOWER AMPLITUDE MEAN FLOW ALOFT SHOULD PREVAIL OVER THE LOWER 48  
AT LEAST FROM FRIDAY THROUGH THE WEEKEND, BEHIND A DEPARTING DEEP  
UPPER LOW WHICH MAY TAKE ITS TIME DRIFTING ACROSS EASTERN CANADA  
INTO NEXT WEEK. GUIDANCE GENERALLY SHOWS A SHORTWAVE AND  
ASSOCIATED RAIN/SNOW PROGRESSING INTO AND THROUGH THE WEST DURING  
THE WEEKEND THEN INTO THE PLAINS/MISSISSIPPI VALLEY BY EARLY NEXT  
WEEK. BY EARLY NEXT WEEK AN UPPER TROUGH REACHING THE EASTERN  
PACIFIC EARLY NEXT WEEK MAY SERVE TO AMPLIFY THE DOWNSTREAM RIDGE  
CROSSING THE WEST AND TROUGH HEADING INTO THE EAST, WITH THE  
PACIFIC TROUGH LIKELY ENTERING THE WEST NEXT TUESDAY AND BRINGING  
ANOTHER EPISODE OF PRECIPITATION TO THE REGION. WITHIN WHAT HAS  
BEEN AN AGREEABLE FORECAST OF THE LARGE SCALE PATTERN, PERSISTENT  
SIGNIFICANT DETAIL DIFFERENCES AT THE SURFACE AND ALOFT KEEP  
CONFIDENCE LOWER THAN DESIRED FOR COVERAGE AND INTENSITY OF  
PRECIPITATION--ESPECIALLY OVER THE EASTERN HALF OF THE COUNTRY  
FROM SUNDAY ONWARD BUT ALSO TO SOME DEGREE OVER THE WEST.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE FIRST HALF OF THE PERIOD STARTED WITH A COMPOSITE OF LATEST  
OPERATIONAL RUNS. THIS PART OF THE FORECAST INVOLVED PRIMARILY  
TIMING ISSUES, WITH THE GFS BEGINNING TO STRAY A BIT FASTER THAN  
MOST OTHER GUIDANCE FOR THE SURFACE FRONT AND SUPPORTING DYNAMICS  
CROSSING NEW ENGLAND DURING THE WEEKEND AND SPREAD/VARIABILITY  
PERSISTING FOR THE SYSTEM REACHING THE WEST BY SATURDAY. THE  
WESTERN SYSTEM HAS SOME DEGREE OF COMPLEXITY, INVOLVING POTENTIAL  
INTERACTION OF A TROUGH/UPPER LOW OFF THE PACIFIC  
NORTHWEST/VANCOUVER ISLAND AND SEPARATE SHORTWAVE JUST TO THE  
SOUTH. THROUGH THE 06Z CYCLE THE GFS WAS ON THE FASTER SIDE OF THE  
SPREAD BUT THE NEW 12Z UKMET HAS ADJUSTED CLOSER TO THE GFS,  
LEAVING THE 00Z ECMWF/ECMWF MEAN A LITTLE ON THE SLOWER SIDE AND  
THE 12Z CMC ESSENTIALLY A COMPROMISE. THE NEW 12Z ECMWF HAS NUDGED  
TO A MIDDLE GROUND AS WELL.  
 
BY THE FIRST PART OF NEXT WEEK, DETAIL ISSUES WITH THE INCOMING  
WESTERN SYSTEM LEAD TO ADDITIONAL DIVERGENCE OF SOLUTIONS AT THE  
SURFACE AND ALOFT OVER THE EAST. THE ECMWF THROUGH 00Z CONTINUED  
TO BE THE MOST CONSISTENT MODEL IN PRINCIPLE WITH DEVELOPMENT OF  
AN EMBEDDED CLOSED LOW ALONG WITH SURFACE SYSTEM WHOSE TRACK IS  
OVER THE MID-LATITUDES OF THE EAST, WITH ITS MEAN AND THE CMC/CMC  
MEAN FAVORING SIMILAR TIMING WHICH IS SLOWER THAN THE GFS/GEFS  
MEAN. THE NEW 12Z GFS/CMC KEEP THE CORE OF THE UPPER TROUGH  
FARTHER NORTH WHICH LEADS TO A MUCH FARTHER NORTH SURFACE LOW  
TRACK THAN WHAT OTHER GUIDANCE HAD BEEN SHOWING THROUGH THE  
00Z/06Z CYCLES. THE 12Z GEFS MEAN HAS ADJUSTED THE SURFACE TRACK  
AT LEAST PARTIALLY IN THE 12Z GFS/CMC DIRECTION. MEANWHILE THE NEW  
12Z UKMET BECOMES A FAST EXTREME WITH GREATER STRENGTH THAN  
CONSENSUS. THE 12Z ECMWF HAS ADJUSTED ITS UPPER SYSTEM NORTHWARD  
SOMEWHAT BUT NOT TO THE EXTENT OF THE GFS/CMC. THE UPPER TROUGH  
REACHING THE WEST BY TUESDAY WAS CLOSER TO CONSENSUS IN THE 00Z  
GFS VERSUS THE FASTER 06Z RUN, WHILE THE 12Z VERSION HAS REVERTED  
BACK TO THE MAJORITY. THE NEW CMC/ECMWF ARE FAIRLY CONSISTENT. THE  
EARLY-PERIOD BLEND BASED ON 00Z-06Z BASED GUIDANCE TRANSITIONED TO  
A MODEL/MEAN MIX TILTED SOMEWHAT MORE TOWARD THE ECMWF/ECMWF MEAN  
RELATIVE TO THE GFS/GEFS, WITH 06Z GFS INPUT SWITCHING TO THE 00Z  
RUN LATE.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
THE DEPARTING LOW PRESSURE SYSTEM NORTH OF THE GREAT LAKES WILL  
LIKELY CONTINUE TO BRING GUSTY WINDS INTO FRIDAY ACROSS THE  
NORTHERN TIER, RESULTING IN BLOWING A DRIFTING OF SNOW AND  
POSSIBLE HAZARDOUS TRAVEL CONDITIONS IN REGIONS THAT RECEIVED  
HEAVY SNOWFALL IN PRIOR DAYS. THIS SYSTEM MAY ALSO PRODUCE SOME  
GENERALLY LIGHT PRECIPITATION ACROSS THE GREAT LAKES/NORTHEAST.  
MOISTURE AND INSTABILITY INTERACTING WITH A WARM FRONT LIFTING  
THROUGH THE SOUTHEAST AND LOWER MISSISSIPPI VALLEY NEXT WEEKEND  
AND APPROACH OF A COLD FRONT FROM THE NORTH SHOULD BRING AREAS OF  
MODERATE TO LOCALLY HEAVY RAINFALL TO PARTS OF THOSE AREAS, BUT  
FOR NOW WITH LOW CONFIDENCE IN EXACT PLACEMENT OF HEAVIEST TOTALS.  
FARTHER WEST, A SYSTEM FORECAST TO REACH THE WEST BY SATURDAY  
SHOULD FOCUS RAIN/MOUNTAIN SNOW OVER THE CENTRAL AND NORTHERN WEST  
COAST INTO THE NORTHERN ROCKIES LATE THIS WEEK INTO THE WEEKEND.  
CURRENTLY THE BEST SIGNAL FOR HEAVIEST TOTALS IS FROM SOUTHWEST  
OREGON INTO NORTHERN CALIFORNIA BUT STILL WITH SOME UNCERTAINTY  
OVER EXACT LOCATION AND MAGNITUDE. MOISTURE SHOULD SPREAD EAST  
BEYOND THE ROCKIES SUNDAY ONWARD AS LOW PRESSURE/FRONTS REACH THE  
CENTRAL/EASTERN U.S. AT LEAST SOME PRECIPITATION ACROSS THE  
NORTHERN TIER MAY BE IN THE FORM OF SNOW WHILE RAINFALL  
COVERAGE/INTENSITY OVER THE EAST WILL DEPEND ON CURRENTLY  
UNCERTAIN SYSTEM DETAILS. THE CENTRAL ROCKIES/HIGH PLAINS COULD  
SEE A BRIEF PERIOD OF STRONG WINDS AROUND SUNDAY WITH SYSTEM  
PASSAGE. EXPECT ANOTHER EPISODE OF PRECIPITATION FROM THE PACIFIC  
NORTHWEST/NORTHERN CALIFORNIA INTO THE NORTHERN ROCKIES EARLY NEXT  
WEEK, WITH SOME ENHANCED TOTALS POSSIBLE OVER FAVORED  
COASTAL/TERRAIN AREAS.  
 
THE CORE OF BELOW NORMAL TEMPERATURES ACROSS THE NORTHERN HIGH  
PLAINS WILL LIKELY PERSIST INTO EARLY NEXT WEEK, WITH DAYTIME  
HIGHS GENERALLY 20-30F BELOW NORMAL. LOCALLY COLDER READINGS  
(ESPECIALLY FOR DAYTIME HIGHS) ARE POSSIBLE LATE THIS WEEK INTO  
THE WEEKEND WITH SOME LINGERING DAILY RECORDS FOR LOWS/COLD HIGHS  
POSSIBLE MAINLY ON FRIDAY. OVER THE WEST, TEMPERATURES SHOULD  
MODERATE IN BETWEEN SYSTEMS AS A PERIOD OF UPPER RIDGING MOVES  
THROUGH. FRIDAY-SATURDAY WILL FEATURE CHILLY READINGS OVER THE  
NORTHERN HALF OF THE REGION (MINUS 10-15F ANOMALIES FOR HIGHS) AND  
CLOSER TO NORMAL TEMPERATURES FARTHER SOUTH. AS THE UPPER RIDGE  
BUILDS OVER THE REGION BY THE START OF NEXT WEEK, NORTHERN  
LOCATIONS SHOULD TREND TOWARD NORMAL AND SOUTHERN AREAS ABOVE  
NORMAL. THE GREAT BASIN AND SOUTHWEST COULD SEE HIGHS AS WARM AS  
10-15F ABOVE NORMAL. THE EAST SHOULD STAY NEAR NORMAL THIS  
WEEKEND, BUT THE SYSTEM POTENTIALLY REACHING THE MIDWEST/EAST  
EARLY NEXT WEEK COULD DRAW SOME OF THE CHILLY NORTHERN PLAINS AIR  
SOUTHWARD AND EASTWARD BEHIND IT, WITH EXPANDING COVERAGE OF MINUS  
10-20F ANOMALIES. THE SOUTHERN PLAINS WILL SEE HIGHS 10-15F ABOVE  
NORMAL FRIDAY-SUNDAY FOLLOWED BY A COOLING TREND.  
 
RAUSCH/SANTORELLI  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, EXPERIMENTAL EXCESSIVE RAINFALL  
OUTLOOK, 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/#PAGE=ERO  
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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