112  
FXUS02 KWBC 271812  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
111 PM EST SUN FEB 27 2022  
 
VALID 12Z WED MAR 2 2022 - 12Z SUN MAR 6 2022  
 
18Z UPDATE: THE 12Z DETERMINISTIC GUIDANCE IS GENERALLY IN ABOVE  
AVERAGE AGREEMENT ON THE LARGE SCALE PATTERN THROUGH THE END OF  
THE WEEK, WITH THE HIGHEST LEVEL OF CONFIDENCE IN THE SOUTHERN  
STREAM AND THE BUILDING UPPER TROUGH OVER THE INTERMOUNTAIN WEST  
BY THE WEEKEND. INITIALLY THE GFS/GEFS IS A BIT STRONGER WITH A  
SHORTWAVE CROSSING THE SOUTH-CENTRAL U.S. FOR THE MIDDLE OF THE  
WEEK, BUT DIFFERENCES AT THE SURFACE ARE LESS NOTICEABLE AND THUS  
STILL COMPARABLE TO THE OTHER GUIDANCE. THE 12Z GFS IS ALSO MORE  
PROGRESSIVE WITH AN EJECTING SHORTWAVE AND SURFACE LOW ACROSS THE  
CENTRAL PLAINS AND MIDWEST BY SATURDAY, AND AHEAD OF ITS ENSEMBLE  
MEAN. THERE IS MORE SPREAD IN THE GUIDANCE ACROSS SOUTHERN CANADA  
FOR THE WEEKEND, AND THE GFS IS MORE OUT OF PHASE WITH THE  
CMC/ECMWF ACROSS EASTERN CANADA. THIS WILL TEND TO INTRODUCE MORE  
UNCERTAINTIES IN THE FORECAST FOR DAYS 6 AND 7. THE WPC FORECAST  
WAS PRIMARILY BASED ON A MULTI-DETERMINISTIC BLEND, INCLUDING THE  
6Z GFS, THROUGH EARLY FRIDAY, AND THEN GRADUALLY INCREASING  
PERCENTAGES OF THE GEFS/ECENS WHILST STILL MAINTAINING SOME OF THE  
00Z ECMWF AND CMC. /HAMRICK  
 
   
..OVERVIEW
 
 
EXPECT A SIGNIFICANT CHANGE IN THE UPPER LEVEL PATTERN OVER THE  
COURSE OF THE PERIOD, WITH A WESTERN U.S. RIDGE/BROAD EASTERN  
TROUGH AS OF WEDNESDAY TRANSITIONING TOWARD AN AMPLIFIED NORTHERN  
PLAINS THROUGH WESTERN U.S. TROUGH/EASTERN RIDGE CONFIGURATION BY  
NEXT WEEKEND. AS THIS EVOLUTION OCCURS, PRECIPITATION OVER THE  
PACIFIC NORTHWEST AND NORTHERN ROCKIES WILL SPREAD ACROSS MORE OF  
THE WEST, TO BE FOLLOWED BY A BROAD AREA OF VARIOUS PRECIPITATION  
TYPES DEVELOPING OVER THE CENTRAL U.S. AS LOW PRESSURE TRACKS  
THROUGH THE PLAINS AND UPPER GREAT LAKES. EARLY IN THE PERIOD A  
NORTHERN TIER WAVE MAY SPREAD SOME SNOW ACROSS AREAS FROM THE  
UPPER MIDWEST INTO THE NORTHEAST. WESTERN/CENTRAL STATES WILL SEE  
A PRONOUNCED COOLER TREND IN TEMPERATURES, FROM WELL ABOVE NORMAL  
TO BELOW NORMAL, WHILE ABOVE NORMAL TEMPERATURES OVER THE SOUTHERN  
HALF OR SO OF THE EAST SHOULD EXPAND NORTHWARD NEXT WEEKEND. FAR  
NORTHERN TIER AREAS WILL TEND TO BE COLDER THAN NORMAL ON MOST  
DAYS.  
   
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
 
 
THE LATEST CYCLES OF GUIDANCE MAINTAIN THE RECENT THEME OF BETTER  
THAN AVERAGE AGREEMENT FOR THE LARGE-SCALE PATTERN EVOLUTION BUT  
CONTINUED DIFFERENCES FOR SOME DETAILS. SUBTLE DIFFERENCES IN  
EVOLUTION OF SOUTHERN CANADA ENERGY FLOWING INTO/THROUGH THE  
EASTERN NORTH AMERICA MEAN TROUGH CONTINUE TO PRODUCE GREATER THAN  
AVERAGE SPREAD FOR THE SPECIFICS OF A SURFACE WAVE THAT MAY TRACK  
FROM THE MIDWEST THROUGH THE NORTHEAST FROM WEDNESDAY INTO EARLY  
THURSDAY. CMC/UKMET RUNS HAVE CONSISTENTLY BEEN ON THE STRONGER  
AND NORTHERN SIDE OF THE MODEL SPREAD FOR THIS WAVE. THE NOTABLE  
CHANGE IN THE PAST DAY HAS BEEN WITH THE 00Z GFS/GEFS MEAN  
TRENDING TO A SLOWER/WEAKER VERSION OF THE CMC/UKMET SCENARIO,  
EXTENDING A MODEST TREND FROM THE 18Z CYCLE. THIS LEAVES THE 12Z  
ECMWF STILL THE NEW 00Z RUN ON THE WEAK AND SUPPRESSED SIDE OF THE  
SPREAD. THE PREFERRED SOLUTION ADJUSTED THE WAVE'S TRACK SOMEWHAT  
NORTHWARD FROM PREVIOUS CYCLE GIVEN RELATIVE SUPPORT FROM THE  
MEANS BUT MAINTAINED A FAIRLY WEAK DEPICTION DUE TO THE  
CONSIDERABLE SPREAD.  
 
MEANWHILE GUIDANCE IS STILL IN THE PROCESS OF REFINING THE  
FORECAST OF UPPER TROUGHING THAT MOVES INTO THE WEST. 00Z RUNS SO  
FAR ARE ADDING SUPPORT TO THE IDEA OF A SLIGHTLY SLOWER/SHARPER  
LEAD SHORTWAVE REACHING THE WEST COAST, LEAVING THE 12Z  
ECMWF/ECMWF MEAN A BIT ON THE FASTER SIDE. THE NEW 00Z ECMWF HAS  
ADJUSTED SLOWER. THIS ENERGY SHOULD ULTIMATELY CROSS THE WEST AND  
EJECT THROUGH THE PLAINS, SUPPORTING A PLAINS THROUGH UPPER GREAT  
LAKES SURFACE SYSTEM FROM LATE WEEK THROUGH THE WEEKEND.  
CONSISTENT WITH TRENDS SEEN FARTHER WEST, THIS SYSTEM HAS ADJUSTED  
A LITTLE SLOWER OVER THE PAST DAY. LOW-PREDICTABILITY TRAILING  
ENERGY DROPPING INTO THE MEAN TROUGH (AS EASTERN PACIFIC RIDGING  
STEADILY BUILDS) CONTINUES TO COMPLICATE THE FORECAST OF THE  
LEADING IMPULSE TO SOME DEGREE. STILL, THERE IS BETTER THAN  
AVERAGE AGREEMENT REGARDING THE FAIRLY DEEP TROUGH FORECAST TO BE  
OVER THE WEST AS OF DAY 7 SUNDAY.  
 
THE 12Z/18Z OPERATIONAL MODEL BLEND USED FOR THE FIRST HALF OF THE  
PERIOD PROVIDED THE DESIRED ADJUSTMENT FOR THE EASTERN U.S. WAVE  
WHILE REPRESENTING AN INTERMEDIATE SOLUTION FOR THE SHORTWAVE  
ENTERING THE WEST. THEN A TREND TOWARD MORE EVEN WEIGHT OF MODELS  
AND ENSEMBLE MEANS LATER IN THE PERIOD ACCOUNTED FOR THE GOOD  
PATTERN AGREEMENT BUT UNCERTAINTY IN SOME OF THE DETAILS.  
   
..WEATHER HIGHLIGHTS/THREATS
 
 
RAIN AND HIGH ELEVATION SNOW FROM THE PACIFIC NORTHWEST/NORTHERN  
CALIFORNIA INTO NORTHERN ROCKIES AS OF MIDWEEK WILL SPREAD ACROSS  
MORE OF THE WEST LATER IN THE WEEK, WHILE TRENDING LIGHTER ALONG  
THE WEST COAST, AS AN UPPER TROUGH MOVES INTO AND THROUGH THE  
REGION. CONTINUED PROGRESSION OF THIS ENERGY SHOULD SUPPORT A  
CENTRAL PLAINS INTO UPPER GREAT LAKES SURFACE LOW AND FRONTAL  
SYSTEM LATE WEEK INTO THE WEEKEND, WITH A CORRESPONDING BROAD AREA  
OF PRECIPITATION OVER THE CENTRAL U.S. BEST POTENTIAL FOR WINTRY  
PRECIPITATION TYPES WILL EXTEND FROM THE NORTHERN HALF OF THE HIGH  
PLAINS INTO THE UPPER GREAT LAKES AND EVENTUALLY NEW ENGLAND, WITH  
A BAND OF SIGNIFICANT SNOW POSSIBLE TO THE NORTHWEST OF THE  
SURFACE LOW TRACK. RAINFALL OF VARYING INTENSITY WILL BE POSSIBLE  
OVER THE REST OF THE CENTRAL/EAST-CENTRAL U.S. WELL AHEAD OF THIS  
SYSTEM, A NORTHERN TIER WAVE MAY SPREAD SNOW ACROSS AN AREA FROM  
THE UPPER MIDWEST INTO NEW ENGLAND FROM WEDNESDAY INTO THURSDAY.  
THUS FAR GUIDANCE HAS NOT BEEN AGREEABLE WITH DETAILS OF THE  
SURFACE WAVE SO COVERAGE AND AMOUNTS OF SNOW HAVE LOWER THAN  
AVERAGE CONFIDENCE. A LOWER-PROBABILITY SCENARIO COULD LEAD TO A  
SOMEWHAT FARTHER SOUTHWARD AXIS.  
 
A MAJORITY OF THE LOWER 48 WILL SEE ABOVE NORMAL TEMPERATURES ON  
WEDNESDAY, WITH AREAS ALONG THE CENTRAL/EASTERN CANADIAN BORDER AS  
WELL AS THE WESTERN GULF COAST BEING THE MAIN EXCEPTIONS. THEN  
THE WEST AND NORTHERN-CENTRAL PLAINS WILL TREND STEADILY COOLER  
WITH TIME WHILE ABOVE NORMAL READINGS OVER THE SOUTHERN HALF OF  
THE EAST EXPAND NORTHWARD BY NEXT WEEKEND. EXPECT THE WARMEST  
ANOMALIES OF PLUS 20-25F OR SO FOR HIGHS TO BE OVER THE CENTRAL  
PLAINS WEDNESDAY THROUGH THURSDAY OR FRIDAY. OTHER WARM AREAS MAY  
SEE PLUS 10-20F ANOMALIES WITH SOME LOCALLY HIGHER READINGS  
POSSIBLE. NORTHERN PLAINS INTO ROCKIES LOCATIONS MAY SEE HIGHS  
10-15F BELOW NORMAL BY NEXT SUNDAY.  
 
RAUSCH/HAMRICK  
 
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  
 

 
 

 
 
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