917  
FXUS02 KWBC 051600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST SAT JAN 05 2019  
 
VALID 12Z TUE JAN 08 2019 - 12Z SAT JAN 12 2019  
   
..OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES
 
 
BROADLY SPEAKING THE GUIDANCE IS FAIRLY CONSISTENT AND AGREEABLE  
REGARDING THE PATTERN OF PROGRESSIVE PACIFIC SYSTEMS WITH AN  
INCREASING TENDENCY TOWARD WESTERN NORTH AMERICA MEAN RIDGING BY  
FRI/SAT, PERHAPS SOMEWHAT MORE PRONOUNCED OVER CANADA AND ALASKA.  
THIS DEVELOPING MEAN RIDGE IS CONSISTENT WITH TELECONNECTIONS  
RELATIVE TO NORTHERN ATLANTIC POSITIVE HEIGHT ANOMALIES AND  
NORTHERN PACIFIC NEGATIVE HEIGHT ANOMALIES IN RECENT D+8 MEAN  
CHARTS. BY NEXT WEEKEND GUIDANCE ALSO APPEARS TO BE HEADING  
TOWARD THE TELECONNECTION-FAVORED EASTERN NORTH AMERICA MEAN  
TROUGHING.  
 
FOR DAYS 3-5 TUE-THU A GENERAL MODEL BLEND REPRESENTS MOST ASPECTS  
OF SIGNIFICANT FEATURES WELL. THE 06Z GFS RUN PROVIDES THE GFS  
INPUT AS THE 00Z CYCLE BROUGHT A SHORTWAVE RIDGE INTO THE PACIFIC  
NORTHWEST/SOUTHWESTERN CANADA AROUND THU WHEREAS CONSENSUS SHOWS  
MORE OF A SHORTWAVE, ALBEIT A WEAK ONE. ALSO OF NOTE THE 00Z  
ECMWF BECOMES SLOWER/MORE AMPLIFIED THAN ABOUT 80 PERCENT OF ECMWF  
ENSEMBLES WITH THE UPPER TROUGH NEAR THE EAST COAST. THERE IS  
GOOD CONTINUITY WITH LOW PRESSURE EXPECTED TO BE NEAR THE NEW  
ENGLAND COAST AS OF 12Z WED. ONE NOTABLE TREND OVER THE PAST 1-2  
DAYS IS EVIDENT UPSTREAM AS BY THU GUIDANCE SHOWS MORE SPLITTING  
OF SHORTWAVE ENERGY MOVING INLAND FROM THE WEST COAST.  
 
BY DAYS 6-7 FRI-SAT LEANS MORE TOWARD THE ENSEMBLE MEANS, WITH  
MORE 00Z ECMWF MEAN WEIGHT RELATIVE TO THE 06Z GEFS. LINGERING  
OPERATIONAL MODEL WEIGHT ALSO SIDED A LITTLE MORE WITH THE 00Z  
ECMWF ESPECIALLY ALONG THE WEST COAST. CONTINUING FROM MID-PERIOD  
THE 00Z ECMWF MAY STILL BE TOO SLOW WITH THE UPPER TROUGH  
DEPARTING FROM THE EAST COAST. THE SPLIT NATURE OF ENERGY  
PROGRESSING FROM THE WESTERN U.S. LEADS TO A SOMEWHAT MORE DIFFUSE  
APPEARANCE OF CENTRAL U.S. LOW PRESSURE BY THE LATTER PART OF NEXT  
WEEK. BEST CONSENSUS NOW SUGGESTS A SUPPRESSED SOUTHERN PLAINS  
INTO GULF OF MEXICO WAVE ASSOCIATED WITH SOUTHERN STREAM SHORTWAVE  
ENERGY WHILE A NORTHERN STREAM COOL PUSH BECOMES BETTER DEFINED BY  
NEXT SAT AS UPPER TROUGHING AMPLIFIES IN RESPONSE TO THE WESTERN  
NORTH AMERICA RIDGE. THE 06Z GFS MAY BECOME A LITTLE TOO  
AMPLIFIED WITH THE SOUTHEAST SIDE OF THIS EASTERN TROUGH ALOFT  
LATE IN THE PERIOD. MEANWHILE ECMWF MEANS HAVE HAD THE EARLIER  
LEAD TIME VERSUS GEFS MEANS ON DEFINING THE UPPER TROUGH  
NEARING/REACHING THE WEST COAST NEXT FRI-SAT. THUS FAR THE  
OPERATIONAL GFS IDEA OF CLOSING OFF A FAIRLY DEEP SOUTHERN STREAM  
LOW IS IN THE MINORITY THOUGH SOME GEFS MEMBERS AND A FEW ECMWF  
MEMBERS OFFER THAT AS A POSSIBLE SOLUTION. FORECAST HISTORY OF  
PRECEDING SYSTEMS IN THIS PROGRESSIVE PATTERN HAS NOT FAVORED THE  
SLOW SIDE OF THE TIMING SPREAD (WHICH IS CURRENTLY REPRESENTED BY  
THE 00Z GFS AND LATEST GEFS MEANS). THESE CONSIDERATIONS FAVOR  
LEANING MORE IN THE ECMWF/ECMWF MEAN DIRECTION FOR THIS PART OF  
THE FORECAST.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE SYSTEM AFFECTING THE NORTHEAST THROUGH MIDWEEK MAY PRODUCE  
SOME HEAVY SNOW OVER NORTHERN NEW ENGLAND AND LAKE EFFECT SNOW  
WILL LINGER FOR A TIME AFTER DEPARTURE OF THE SYSTEM. A TIGHT  
GRADIENT BETWEEN THIS SYSTEM AND TRAILING HIGH PRESSURE WILL  
LIKELY PRODUCE A COUPLE DAYS OF BRISK WINDS OVER THE EASTERN  
STATES. MEANWHILE A STRONG SYSTEM OFF THE WEST COAST AS OF EARLY  
TUE SHOULD TRACK NORTHWARD AND REMAIN OFFSHORE BUT LEADING FLOW  
WILL BRING ANOTHER EPISODE OF HEAVY RAIN/MOUNTAIN SNOW TO THE WEST  
COAST STATES WITH NORTHERN CALIFORNIA AND PARTS OF THE PACIFIC  
NORTHWEST LIKELY TO SEE THE HIGHEST TOTALS. WINDS MAY ALSO BE  
STRONG AT TIMES. EXPECT SOME OF THIS MOISTURE TO REACH THE  
NORTHERN ROCKIES THROUGH MIDWEEK. ASSOCIATED SHORTWAVE ENERGY  
PROGRESSING INLAND SHOULD PROMOTE AN INCREASE IN RAINFALL  
COVERAGE/INTENSITY OVER TEXAS AND POSSIBLY SOME AREAS TO THE  
EAST/NORTHEAST DEPENDING ON SPECIFICS OF FLOW ALOFT. ANY MOISTURE  
THAT REACHES CENTRAL LATITUDES BY NEXT WEEKEND COULD BE IN THE  
FORM OF SNOW. THERE MAY BE A SEPARATE AREA OF MOSTLY LIGHT SNOW  
ACROSS EXTREME NORTHERN AREAS EXTENDING INTO THE GREAT LAKES. THE  
NEXT PACIFIC SYSTEM SHOULD BRING ANOTHER AREA OF MOISTURE TO THE  
WEST COAST AROUND FRI-SAT. BEST PRECIPITATION POTENTIAL MAY  
EXTEND FARTHER SOUTH THROUGH CALIFORNIA THAN WITH THE PREVIOUS  
SYSTEM.  
 
TUE INTO WED WILL BE QUITE WARM VERSUS AVERAGE OVER THE EASTERN  
HALF OF THE U.S. WITH MORNING LOWS 10-25F ABOVE NORMAL AND TUE  
HIGHS GENERALLY 10-20F ABOVE NORMAL. HIGHS OVER THE EAST WILL  
THEN TREND TO NEAR OR A LITTLE BELOW NORMAL WHILE LOWS SHOULD BE A  
TAD MORE MODERATE. UPSTREAM PROGRESSION WILL BRING ANOTHER AREA  
OF WARMTH ACROSS THE CENTRAL U.S. MID-LATE WEEK WITH HIGHEST  
ANOMALIES OVER NORTHERN LOCATIONS. TEMPERATURES OVER THE  
PLAINS/MISSISSIPPI VALLEY SHOULD BEGIN TO TREND COOLER NEXT SAT  
AFTER COLD FRONTAL PASSAGE. OVER THE WEST THE ACTIVE PATTERN WILL  
TEND TO KEEP HIGHS NEAR TO BELOW NORMAL, WITH LOWS ABOVE NORMAL  
ESPECIALLY TUE-THU.  
 
RAUSCH  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES ARE FOUND 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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