693  
FXUS02 KWBC 130649  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
249 AM EDT WED APR 13 2022  
 
VALID 12Z SAT APR 16 2022 - 12Z WED APR 20 2022  
 
   
..OVERVIEW
 
 
LOWER AMPLITUDE MEAN FLOW ALOFT SHOULD PREVAIL OVER THE LOWER 48  
AT LEAST 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.  
MEANWHILE, AN UPPER TROUGH REACHING THE EASTERN PACIFIC BY MONDAY  
MAY SERVE TO AMPLIFY THE OVERALL FLOW WITH POTENTIAL FOR A CLOSED  
LOW OVER THE GREAT LAKES/MIDWEST AROUND NEXT MONDAY-TUESDAY AND  
INTO THE NORTHEAST BY WEDNESDAY. WITHIN WHAT HAS BEEN A DECENTLY  
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. THERE'S ALSO SOME INITIAL  
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. THE 18Z GFS AND 12Z UKMET BOTH WERE FASTER THAN THE  
ECMWF AND CMC. THE UKMET IS ALSO THE QUICKEST/FARTHEST SOUTH TO  
CLOSE OFF A LOW OVER THE OHIO VALLEY AND WAS NOT INCLUDED IN THE  
BLEND FOR TONIGHT. BY DAYS 6-7, THE ECMWF AND THE ECENS MEAN BOTH  
BECOME NOTICEABLY SLOWER WITH THE UPPER SYSTEM THROUGH THE  
NORTHEAST, WITH THE CMC CONTINUING TO BE A NICE MIDDLE GROUND  
(ALONG WITH THE NAEFS MEAN). THE NEW 00Z RUNS ACTUALLY LOOK A  
LITTLE MORE AGREEABLE, WITH THE GFS SLOWING A BIT AND THE ECMWF A  
LITTLE FASTER THAN THE PREVIOUS RUN. THE 00Z UKMET REMAINS A  
FAST/SOUTH OUTLIER. THE NEXT SYSTEM ENTERS THE WEST COAST EARLY  
NEXT WEEK WITH AGAIN, THE GFS A FAST/STRONGER OUTLIER AND WANTING  
TO CLOSE OFF AN UPPER LOW OVER THE NORTHERN PLAINS/UPPER  
MISSISSIPPI VALLEY NEXT WEDNESDAY. PREFER A BLEND TOWARDS THE  
SLOWER ECMWF/CMC ALONG WITH MODEST INCLUSION OF THE NAEFS/ECENS  
ENSEMBLE MEANS FOR THE LATER PERIODS.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
THE DEPARTING LOW PRESSURE SYSTEM NORTH OF THE GREAT LAKES SHOULD  
CONTINUE TO PRODUCE SOME GENERALLY LIGHT TO MODERATE PRECIPITATION  
ACROSS THE GREAT LAKES/NORTHEAST AS A SECONDARY SURFACE LOW LIFTS  
OFF THE COAST. MOISTURE AND INSTABILITY INTERACTING WITH A WARM  
FRONT LIFTING THROUGH THE SOUTHEAST AND LOWER MISSISSIPPI VALLEY  
THIS 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 CONTINUE TO FOCUS RAIN/MOUNTAIN SNOW OVER THE  
CENTRAL AND NORTHERN WEST COAST INTO THE NORTHERN ROCKIES LATE  
THIS WEEK INTO THE WEEKEND. 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, AND MODERATING SLOWLY WITH  
TIME. OVER THE WEST, TEMPERATURES SHOULD MODERATE IN BETWEEN  
SYSTEMS AS A PERIOD OF UPPER RIDGING MOVES THROUGH. 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 ON SATURDAY, 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 NEXT WEEKEND FOLLOWED BY A  
COOLING TREND.  
 
SANTORELLI/RAUSCH  
 
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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