485  
FXUS02 KWBC 010700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
159 AM EST TUE MAR 01 2022  
 
VALID 12Z FRI MAR 04 2022 - 12Z TUE MAR 08 2022  
 
...HEAVY SNOW POTENTIAL OVER THE UPPER MIDWEST/GREAT LAKES AND  
POSSIBLY INTO NORTHERN NEW ENGLAND DURING THE WEEKEND...  
 
...HEAVY RAINFALL POTENTIAL FROM THE MID-LOWER MISSISSIPPI VALLEY  
INTO TENNESSEE/OHIO VALLEYS LATE WEEKEND INTO EARLY NEXT WEEK...  
   
..OVERVIEW
 
 
MODELS AND ENSEMBLE MEANS CONTINUE TO SHOW THE ESTABLISHMENT OF A  
POSITIVELY TILTED MEAN TROUGH ALOFT FROM CANADA INTO THE WESTERN  
U.S., BETWEEN A BUILDING EASTERN PACIFIC RIDGE AND ANOTHER RIDGE  
THAT MIGRATES ACROSS THE GULF OF MEXICO INTO THE BAHAMAS. A  
LEADING IMPULSE REACHING THE WEST BY THE START OF THE PERIOD EARLY  
FRIDAY AND ANOTHER FEATURE ARRIVING CLOSE BEHIND WILL BRING  
PRECIPITATION TO PORTIONS OF THE WEST, FOLLOWED BY A BROAD AREA OF  
PRECIPITATION TO THE EAST OF THE ROCKIES AS TWO POTENTIAL SYSTEMS  
TRACK INTO THE GREAT LAKES/OHIO VALLEY. THE FIRST SYSTEM SHOULD  
BRING GREATER SNOWFALL POTENTIAL TO THE UPPER MIDWEST/UPPER GREAT  
LAKES AND TO SOME DEGREE NORTHERN NEW ENGLAND. MOST GUIDANCE  
SHOWS A SECOND SYSTEM DEVELOPING ALONG THE TRAILING FRONT WHOSE  
SLOW MOVEMENT DUE TO ALIGNMENT WITH SOUTHWESTERLY MEAN FLOW ALOFT  
LATE WEEKEND INTO EARLY NEXT WEEK COULD MAKE IT A FOCUS FOR  
SIGNIFICANT RAINFALL FARTHER SOUTH. BELOW NORMAL TEMPERATURES  
WILL SETTLE OVER MUCH OF THE WESTERN AND CENTRAL U.S. WHILE ABOVE  
NORMAL READINGS FROM THE CENTRAL/SOUTHERN PLAINS INTO THE  
SOUTHEAST LATE THIS WEEK BECOME MORE PRONOUNCED OVER THE EAST.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
WITHIN WHAT CONTINUES TO BE A CONSISTENTLY AGREEABLE PATTERN FROM  
A MULTI-DAY MEAN PERSPECTIVE, OPERATIONAL MODELS CONTINUE TO SHOW  
SOME SPREAD AND VARIABILITY FOR DETAILS AND ARE STILL IN THE  
PROCESS OF REFINING SOME OF THE SPECIFICS UP TO 5-6 DAYS OUT IN  
TIME. THERE ARE SOME COMMON THEMES THOUGH. LATEST RUNS ARE  
SUGGESTING THAT THE LEADING SHORTWAVE REACHING THE WEST BY FRIDAY  
MAY BE IN THE FORM OF A COMPACT CLOSED LOW THAT CROSSES CALIFORNIA  
AND THEN EJECTS RAPIDLY NORTHEASTWARD (WITH MIXED SIGNALS FOR  
BEING OPEN OR CLOSED AT VARIOUS VALID TIMES). THEN CURRENT  
CONSENSUS SHOWS THE NEXT PIECE OF ENERGY DROPPING INTO THE MEAN  
TROUGH AS A CLOSED LOW THAT ALSO TRACKS THROUGH THE WEST AND  
CONTINUES NORTHEASTWARD. MODELS AND ENSEMBLES HAVE MAINTAINED  
REASONABLE CONTINUITY IN HAVING THE LEADING SHORTWAVE SUPPORT  
PLAINS INTO UPPER GREAT LAKES LOW PRESSURE FROM LATE FRIDAY INTO  
SUNDAY BUT WITH A LOT OF VARIABILITY FOR STRENGTH IN THE GREAT  
LAKES. OVER THE PAST COUPLE DAYS THERE HAD BEEN SOME SIGNIFICANT  
WAFFLING IN THE GFS/ECMWF BETWEEN STRONGER AND WEAKER SOLUTIONS  
BUT LATEST RUNS INCLUDING THOSE FROM THE 00Z CYCLE ARE IN THE  
MIDDLE TO DEEPER HALF OF THE ENVELOPE. GUIDANCE STILL SIGNALS  
POTENTIAL FOR SOME WEAKENING BEYOND THE GREAT LAKES AS THE ENERGY  
ALOFT MAY SHEAR OUT TO SOME DEGREE. LATEST GFS/ECMWF RUNS AND  
THEIR MEANS INDICATE THAT THE SECOND EJECTING WESTERN IMPULSE MAY  
LEAD TO ANOTHER WAVE THAT REACHES THE GREAT LAKES OR OHIO VALLEY  
ON A TRACK FARTHER SOUTHEAST THAN THE FIRST ONE AND ONLY ABOUT A  
DAY BEHIND. SUCH A WAVE IS LESS DEFINED IN THE 00Z CMC. DETAILS  
OF ENERGY BEHIND THE SECOND FEATURE BECOME INCREASINGLY UNCERTAIN,  
AS SEEN IN DIFFERENCES AMONG THE OPERATIONAL MODELS AS WELL AS  
BROADENING SPREAD AMONG ENSEMBLE MEMBERS.  
 
THE UPDATED FORECAST STARTED WITH PRIMARY EMPHASIS ON THE 18Z  
GFS/12Z ECMWF WITH LESSER INPUT FROM THE 12Z CMC/UKMET FOR ABOUT  
THE FIRST HALF OF THE PERIOD, TO REFLECT AN INTERMEDIATE SOLUTION  
AMONG THE GENERAL CLUSTERING THAT EXISTED FOR THE TWO PRIMARY  
UPPER SYSTEMS AND CORRESPONDING SURFACE REFLECTION. THE GREATER  
UNCERTAINTY WITH DETAILS OF TRAILING FLOW LED TO TRENDING THE  
BLEND TOWARD HALF MODELS/HALF MEANS BY DAY 7 TUESDAY. THIS  
APPROACH YIELDED GENERALLY MODEST REFINEMENTS TO CONTINUITY.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
THE SEQUENCE OF TWO UPPER SYSTEMS MOVING INTO AND THROUGH THE WEST  
FROM LATE THIS WEEK THROUGH THE WEEKEND SHOULD SPREAD RAIN AND  
HIGHER ELEVATION SNOW ACROSS THE REGION. MOST ACTIVITY SHOULD BE  
LIGHT TO MODERATE BUT SOME LOCALLY HEAVIER TOTALS WILL BE  
POSSIBLE, PRIMARILY FROM THE SIERRA NEVADA INTO THE CENTRAL  
ROCKIES. WITH MUCH LOWER CONFIDENCE, ANOTHER SYSTEM THAT MAY DROP  
SOUTHEASTWARD INTO THE NORTHWEST EARLY NEXT WEEK MAY PRODUCE SOME  
LIGHT TO MODERATE PRECIPITATION.  
 
MEANWHILE WEATHER WILL BECOME MORE ACTIVE ACROSS MANY AREAS TO THE  
EAST OF THE ROCKIES FROM THE END OF THIS WEEK INTO EARLY NEXT  
WEEK. THE FIRST WESTERN FEATURE SHOULD GENERATE SURFACE LOW  
PRESSURE THAT TRACKS FROM THE CENTRAL PLAINS THROUGH UPPER GREAT  
LAKES DURING THE WEEKEND. THE BEST POTENTIAL FOR WINTRY  
PRECIPITATION TYPES STILL EXTENDS FROM THE NORTHERN HALF OF THE  
HIGH PLAINS INTO THE UPPER GREAT LAKES AND EVENTUALLY NEW ENGLAND  
(WHERE A CHANGEOVER TO RAIN MAY OCCUR). HIGHEST PROBABILITY OF  
SIGNIFICANT SNOWFALL REMAINS OVER THE UPPER MIDWEST, JUST TO THE  
NORTHWEST OF THE SURFACE LOW TRACK. LATEST GUIDANCE SUGGESTS THE  
STORM COULD BE STRONG ENOUGH TO PRODUCE SOME BRISK WINDS BUT MODEL  
BEHAVIOR THUS FAR OFFERS POTENTIAL FOR ADDITIONAL CHANGES IN THE  
FORECAST. RAINFALL OF VARYING INTENSITY WILL BE POSSIBLE OVER THE  
REST OF THE CENTRAL/EAST-CENTRAL U.S. AHEAD OF THE TRAILING COLD  
FRONT. THEN THERE IS A CONTINUED SIGNAL FOR HEAVIER RAINFALL  
POTENTIAL GENERALLY WITHIN AN AREA FROM THE SOUTHEASTERN PLAINS  
INTO THE OHIO/TENNESSEE VALLEYS BY SATURDAY NIGHT/SUNDAY INTO  
EARLY NEXT WEEK. THIS THREAT CORRESPONDS TO SLOWER PROGRESSION OF  
THE TRAILING FRONT AS IT BECOMES MORE ALIGNED WITH FLOW ALOFT,  
INTERACTION WITH LOW LEVEL GULF MOISTURE, AND THE POSSIBILITY OF  
ANOTHER WAVE THAT WOULD PROVIDE ADDED RAINFALL FOCUS. THE  
NORTHWESTERN FRINGE OF THIS MOISTURE SHIELD SHOULD CONTAIN SOME  
WINTRY WEATHER, LIKELY ALONG AN AXIS SOMEWHAT SOUTHEAST OF THE  
FIRST EPISODE. SPECIFICS WILL DEPEND ON LOWER-CONFIDENCE WAVE  
DETAILS.  
 
COLDER AIR OVERSPREADING THE WESTERN AND CENTRAL U.S. LATE THIS  
WEEK INTO THE WEEKEND AND PERSISTING THROUGH AT LEAST EARLY NEXT  
WEEK SHOULD YIELD A BROAD AREA OF TEMPERATURES THAT ARE 5-15F  
BELOW NORMAL. SOME POCKETS OF COLDER ANOMALIES ARE POSSIBLE OVER  
THE NORTHERN/CENTRAL HIGH PLAINS. LEADING WARM SECTOR AIR,  
INITIALLY FOCUSED OVER THE CENTRAL PLAINS AND THEN BECOMING MORE  
PRONOUNCED OVER THE EAST, WILL CONTAIN READINGS THAT ARE 10-25F  
ABOVE NORMAL WITH LOCALIZED HIGHER ANOMALIES POSSIBLE FOR MORNING  
LOWS. NUMEROUS LOCATIONS OVER THE SOUTHEAST MAY CHALLENGE DAILY  
RECORD HIGHS FROM THE WEEKEND INTO EARLY NEXT WEEK, WHILE RECORD  
WARM LOWS MAY EXTEND FARTHER NORTHWARD.  
 
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, 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  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page