142  
FXUS02 KWBC 251934  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
234 PM EST MON FEB 25 2019  
 
VALID 12Z THU FEB 28 2019 - 12Z MON MAR 04 2019  
   
..PATTERN OVERVIEW
 
 
EXPECT PROGRESSIVE AND BROADLY CYCLONIC MEAN FLOW ALOFT OVER THE  
LOWER 48. AS AN UPPER RIDGE INITIALLY EXTENDING FROM THE GULF OF  
ALASKA INTO THE ARCTIC DRIFTS INTO NORTHWESTERN CANADA, A DEEP  
SOUTH-CENTRAL CANADA UPPER LOW WILL DESCEND TOWARD THE UPPER GREAT  
LAKES REGION THIS WEEKEND AND CONTINUE RAPIDLY EASTWARD. FLOW  
AROUND THIS LOW MAY INTERACT WITH ENERGY FROM A PACIFIC NORTHWEST  
COAST UPPER LOW THAT OPENS UP AS IT EJECTS INLAND. THE COMBINATION  
OF THESE FEATURES STILL OFFERS SOME POTENTIAL TO PRODUCE AN OHIO  
VALLEY/GREAT LAKES INTO NORTHEAST STORM SYSTEM FRI INTO THE  
WEEKEND, BUT GUIDANCE HAS BECOME MORE UNCERTAIN WITH THIS FEATURE  
AND LATEST WPC PROGS HAVE BACKED OFF ON SYSTEM STRENGTH. MEANWHILE  
ANOTHER PACIFIC SYSTEM WILL LIKELY REACH THE WEST COAST BY THE  
WEEKEND. ANTICIPATE HIGHEST PRECIPITATION TOTALS OVER FAVORED  
TERRAIN FROM CA TO THE CENTRAL ROCKIES AND WITH LESS CERTAINTY FOR  
THE EASTERN THIRD OF THE NATION, WHILE MUCH BELOW NORMAL  
TEMPERATURES PERSIST OVER THE N-CENTRAL U.S.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
MODELS AND ENSEMBLES OFFER REASONABLE FORECAST CLUSTERING FOR  
MID-LARGER SCALE SYSTEMS EFFECTING THE NATION, WITH A NOTICABLE  
EXCEPTION MAINLY OVER THE EASTERN THIRD OF THE COUNTRY. GUIDANCE  
HAS INCREASINGLY BROKEN INTO TWO FORECAST CAMPS FRIDAY INTO THE  
WEEKEND WITH THE GFS/FV3 AND GEFS MEMBERS SHOWING SUBSTANTIALLY  
MORE STORM THREAT OVER THE EASTERN THIRD OF COUNTRY THAN THE  
ECMWF/UKMET/CANADIAN OR ECMWF ENSEMBLES. RECENT STORM HISTORY, WPC  
CONTINUITY, AND CONSISTENT RUN-RUN GFS/FV3/GEFS GUIDANCE HAS  
BECOME MORE SUSPECT CONSIDERING EXPECTED PATTERN  
TRANSITION/DEAMPLIFICATION AND ECMWF/UKMET/CANADIAN OR ECMWF  
ENSEMBLES GUIDANCE THAT HAS STRONGLY TRENDED AWAY FROM HAVING  
SHORT RANGE CLOSED LOW ENERGY EJECT SO BODILY DOWNSTREAM. GIVEN  
UNCERTAINTY, WPC PROGS HAVE BACKED AWAY SOMEWHAT FROM SYSTEM  
DEVELOPMENT AND ASSOCIATED HEAVIER SNOW/RAIN THREATS.  
 
OVERALL, OPTED TP COMPOSITE BLEND THE 06 UTC GEFS MEAN WITH THE 00  
UTC ECMWF ENSEMBLE MEAN TO CREATE THE WPC SURFACE FRONTS/PRESSURES  
AND 500MB PROGS FOR THE WHOLE DOMAIN.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
DURING THU-FRI THE INITIAL FLOW OF MOISTURE OVER THE WEST WILL  
BRING AREAS OF RAIN AND HIGHER ELEVATION SNOW TO ABOUT THE  
NORTHERN 2/3 OF THE REGION WITH A BRIEF DRYING TREND PROGRESSING  
FROM WEST TO EAST. THE NEXT PACIFIC SYSTEM SHOULD START TO BRING  
MOISTURE INTO CALIFORNIA BY THE START OF THE WEEKEND WITH  
RAIN/MOUNTAIN SNOW THEN SPREADING EASTWARD INTO THE ROCKIES. FOR  
THE 5-DAY PERIOD EXPECT AN AREA OF ENHANCED PRECIPITATION FROM  
N-CENTRAL CALIFORNIA/SOUTHWEST OREGON TO THE NORTH-CENTRAL/CENTRAL  
ROCKIES WITH HIGHEST TOTALS LIKELY OVER WINDWARD TERRAIN OF THE  
SIERRA NEVADA RANGE.  
 
LATE THIS WEEK DIFFUSE SHORTWAVE ENERGY MAY ASSIST IN PRODUCING  
RAINFALL OF VARYING INTENSITY OVER THE SOUTHERN HALF OF THE EAST  
WHILE THE NORTHERN FRINGE OF THE MOISTURE SHIELD COULD CONTAIN A  
LITTLE LIGHT SNOW FROM THE MID MISSISSIPPI VALLEY INTO THE  
NORTHERN MID-ATLANTIC. THE POTENTIAL DEVELOPMENT OF A ORGANIZED  
LOW REACHING THE NORTHEAST THIS WEEKEND WOULD INITIALLY SPREAD  
SNOW ACROSS PARTS OF THE NORTHERN PLAINS LATE THIS WEEK WITH  
PRECIPITATION COVERAGE THEN EXPANDING OVER THE EASTERN STATES, BUT  
CONFIDENCE IN THIS SYSTEM IS REDUCED AS GUIDANCE FORECAST SPREAD  
INCREASES. IF DEEPER DEVELOPMENT OCCURS, BEST SNOWFALL POTENTIAL  
WOULD EXTEND FROM THE MIDWEST THROUGH THE GREAT LAKES TO NEW  
ENGLAND. POCKETS OF LOCALLY MODERATE-HEAVY RAINFALL MAY BE  
POSSIBLE OVER THE SOUTH, BUT THUS FAR WITH NO COHERENT SIGNAL IN  
THE GUIDANCE FOR PRECISE LOCATION/MAGNITUDE. THIS SYSTEM MAY  
PRODUCE STRONG WINDS OVER SOME AREAS, BUT NOT TO THE MAGNITUDE OF  
THE SYSTEM CURRENTLY AFFECTING THE GREAT LAKES/NORTHEAST. EXPECT A  
PERIOD OF LAKE EFFECT SNOW IN THE WAKE OF THIS SYSTEM WHILE  
LINGERING MOISTURE ALONG SOUTHERN LATITUDES MAY PRODUCE SOME RAIN  
NEAR THE GULF COAST INTO EARLY NEXT WEEK. IN THE WAKE OF THIS  
SYSTEM, A STRONG SURGE OF VERY COLD AIR WILL SPREAD SOUTH AND EAST  
ACROSS THE CENTRAL/EASTERN U.S. FROM LATE WEEK ONWARD, WITH THE  
COLDEST ANOMALIES SPREADING OUT FROM THE NORTHERN PLAINS. EXPECT  
BEST POTENTIAL FOR DAILY RECORDS TO BE FOR COLD DAYTIME HIGHS OVER  
THE NORTHERN-CENTRAL PLAINS AND MIDWEST DURING THE WEEKEND.  
 
BULLET POINTS FROM MEDIUM RANGE HAZARDS CHART:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
HEAVY PRECIPITATION ACROSS PORTIONS OF CALIFORNIA AND THE  
SOUTHWEST, SAT-SUN, MAR 2-MAR 3.  
HEAVY RAIN ACROSS PORTIONS OF THE SOUTHEAST AND THE LOWER  
MISSISSIPPI VALLEY, MON, MAR 4.  
HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL PLAINS, THE CENTRAL  
ROCKIES, THE CENTRAL GREAT BASIN, THE SOUTHERN PLAINS, THE  
NORTHERN GREAT BASIN, THE SOUTHERN ROCKIES, CALIFORNIA, THE  
PACIFIC NORTHWEST, AND THE SOUTHWEST, SAT-MON, MAR 2-MAR 4.  
HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL PLAINS, THE CENTRAL  
GREAT BASIN, THE NORTHERN PLAINS, THE NORTHERN ROCKIES, THE  
CENTRAL ROCKIES, AND THE NORTHERN GREAT BASIN, THU-FRI, FEB 28-MAR  
1.  
HEAVY SNOW ACROSS PORTIONS OF THE NORTHEAST AND THE GREAT LAKES,  
SAT-SUN, MAR 2-MAR 3.  
FLOODING POSSIBLE ACROSS PORTIONS OF THE TENNESSEE VALLEY, THE  
MIDDLE MISSISSIPPI VALLEY, THE MID-ATLANTIC, THE SOUTHERN  
APPALACHIANS, THE SOUTHEAST, AND THE OHIO VALLEY.  
FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE LOWER  
MISSISSIPPI VALLEY, THE TENNESSEE VALLEY, THE MIDDLE MISSISSIPPI  
VALLEY, THE MID-ATLANTIC, THE SOUTHERN APPALACHIANS, THE  
SOUTHEAST, THE PACIFIC NORTHWEST, AND THE OHIO VALLEY.  
FLOODING LIKELY ACROSS PORTIONS OF THE TENNESSEE VALLEY, THE  
MIDDLE MISSISSIPPI VALLEY, THE MID-ATLANTIC, THE SOUTHERN  
APPALACHIANS, THE SOUTHEAST, AND THE OHIO VALLEY.  
MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL  
PLAINS, THE GREAT LAKES, THE LOWER MISSISSIPPI VALLEY, THE CENTRAL  
APPALACHIANS, THE NORTHERN PLAINS, THE TENNESSEE VALLEY, THE  
PACIFIC NORTHWEST, THE NORTHERN ROCKIES, THE CENTRAL ROCKIES, THE  
MIDDLE MISSISSIPPI VALLEY, THE NORTHEAST, THE SOUTHERN  
APPALACHIANS, THE NORTHERN GREAT BASIN, THE UPPER MISSISSIPPI  
VALLEY, THE MID-ATLANTIC, THE SOUTHERN PLAINS, AND THE OHIO  
VALLEY, THU-MON, FEB 28-MAR 4.  
 
SCHICHTEL  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION AND WINTER WEATHER OUTLOOK  
PROBABILITIES 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  
 

 
 
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