203  
FXUS02 KWBC 031558  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1058 AM EST SUN MAR 03 2019  
 
VALID 12Z WED MAR 06 2019 - 12Z SUN MAR 10 2019  
   
..OVERVIEW
 
 
THE FLOW ACROSS THE CONUS WILL BEGIN THE MEDIUM RANGE IN A RATHER  
AMPLIFIED SETUP, AND THEN GRADUALLY TREND MORE ZONAL AND  
PROGRESSIVE BY THE MID TO LATTER PORTION OF THE FORECAST PERIOD AS  
A BROAD UPPER TROUGH INITIALLY IN PLACE ACROSS THE GREAT  
LAKES/NORTHEAST LIFTS OUT.. SHORTWAVE ENERGY EJECTING FROM A MEAN  
UPPER TROUGH OFF THE WEST COAST WILL CROSS THE COUNTRY EVERY  
COUPLE DAYS. A MORE SIGNIFICANT SHORTWAVE APPEARS LIKELY TO  
GENERATE ANOTHER ENERGETIC LOW PRESSURE SYSTEM ACROSS THE CENTRAL  
U.S. BY NEXT WEEKEND.  
 
   
..MODEL GUIDANCE EVALUATION AND PREFERENCES
 
 
MODELS/ENSEMBLES CONTINUED TO SHOW GOOD CLUSTERING EARLY IN THE  
MEDIUM RANGE WITH RESPECT TO A MID/UPPER-LEVEL SHORTWAVE AND  
SURFACE LOW MOVING INTO CALIFORNIA ON WED. AS THE FEATURE MOVES  
INLAND THU-FRI, CONSENSUS HAS IMPROVED SOMEWHAT ON THE AMPLITUDE,  
WITH THE GFS SHOWING A SIGNIFICANT REDUCTION IN THE AMPLITUDE OF  
THE WAVE AS IT CROSSES THE ROCKIES AND MOVES INTO THE CENTRAL  
U.S., AND A MUCH MORE SUPPRESSED FRONTAL WAVE BY FRI COMPARED TO  
PREVIOUS RUNS. GIVEN THE IMPROVED CONSENSUS, A MULTI-MODEL  
DETERMINISTIC BLEND (00Z ECMWF/UKMET/CMC AND 06Z GFS) WAS  
PREFERRED FROM WED-FRI (DAYS 3-5). THERE IS GENERAL CONSENSUS NOW  
THAT THE DEVELOPMENT OF A MORE SIGNIFICANT WAVE OF LOW PRESSURE  
ACROSS THE CENTRAL U.S. SHOULD HOLD OFF UNTIL SAT WHEN THE NEXT  
SIGNIFICANT SHORTWAVE APPROACHES. THE ECMWF AND GFS SHOWED BETTER  
THAN AVERAGE CONSENSUS WITH RESPECT TO THIS NEXT WAVE AN THE  
RESULTANT SURFACE LOW, WHICH SHOULD DEVELOP IN THE CENTRAL HIGH  
PLAINS FRI NIGHT-SAT AND THEN LIFT NORTHEASTWARD INTO THE MIDWEST  
BY SAT NIGHT-SUN. ADDITIONALLY, SOME SEMBLANCE OF CLUSTERING OF  
ENSEMBLE MEMBERS WAS ALSO EVIDENT WITH THIS FEATURE THROUGH SUN.  
SPREAD IS HIGHER WITH RESPECT TO ANOTHER SHORTWAVE PERHAPS  
APPROACHING THE WEST COAST ON SUN, WITH SOME SOLUTIONS KEEPING THE  
FEATURE OFFSHORE AS A CLOSED LOW (GFS/CMC), WHILE THE ECMWF SHOWS  
A MORE OPEN WAVE. GIVEN THESE CONSIDERATIONS, WEIGHTING OF THE  
ECENS AND GEFS ENSEMBLE MEANS WAS INCREASED TO COMPRISE A MAJORITY  
OF THE FORECAST DURING DAYS 6-7 (SAT-SUN), WITH SOME CONTINUED  
MINOR EMPHASIS ON THE DETERMINISTIC ECMWF AND GFS SOLUTIONS.  
 
   
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
 
 
ALTHOUGH THE COLDEST TEMPERATURES WILL BE PRIOR TO THE START OF  
THIS FORECAST PERIOD, IT WILL STILL BE VERY COLD BY EARLY MARCH  
STANDARDS ACROSS MUCH OF THE CENTRAL AND EASTERN U.S. ON WEDNESDAY  
AND THURSDAY. A LARGE ARCTIC HIGH WILL ENCOMPASS MUCH OF THE U.S.  
EAST OF THE ROCKIES, AND TEMPERATURES ONLY SLOWLY MODERATE BY THE  
END OF THE WEEK WITH ANOMALIES OF 15 TO 30 DEGREES BELOW NORMAL  
THROUGH THURSDAY, AND A SECOND SURGE OF COLD TEMPERATURES IS  
EXPECTED FOR THE NORTHERN PLAINS AND UPPER MIDWEST THROUGH NEXT  
WEEKEND, KEEPING READINGS ABOUT 20 DEGREES BELOW NORMAL. HOWEVER,  
MUCH OF THE SOUTHERN AND EASTERN U.S. WARMS UP TO NEAR AVERAGE  
LEVELS BY THE WEEKEND AS A STORM SYSTEM GATHERS STRENGTH ACROSS  
THE PLAINS.  
 
HEAVY RAIN AND MOUNTAIN SNOW RETURN TO THE WESTERN U.S. BY TUESDAY  
NIGHT AS AN ATMOSPHERIC RIVER EVENT ACCOMPANIES A STRONG PACIFIC  
LOW HEADED TOWARDS CALIFORNIA. THE SIERRA NEVADA WILL LIKELY GET  
AN ADDITIONAL 1 TO 3 FEET OF SNOW, THUS ADDING TO ITS EXTENSIVE  
SNOW PACK. SIGNIFICANT SNOW IS FORECAST FOR THE CENTRAL AND  
NORTHERN ROCKIES ON WEDNESDAY AND THURSDAY AS THE MOISTURE PLUME  
ADVECTS INLAND, ALBEIT NOT TO THE SAME DEGREE AS CALIFORNIA.  
 
WITH A LARGE STORM SYSTEM POSSIBLY AFFECTING THE CENTRAL U.S. NEXT  
WEEKEND, WIDESPREAD RAIN IS EXPECTED TO DEVELOP FROM PORTIONS OF  
THE LOWER/MID-MISSISSIPPI VALLEY TO THE TENNESSEE VALLEY AND  
SOUTHERN APPALACHIANS AS A RICH SUPPLY OF GULF MOISTURE SURGES  
NORTHWARD. DEPENDING ON WHERE THE SURFACE LOW DEVELOPS, A BAND OF  
HEAVY SNOW AND WINDY CONDITIONS ARE POSSIBLE ACROSS PARTS OF THE  
NORTHERN PLAINS, UPPER MIDWEST, AND WESTERN GREAT LAKES REGION.  
 
RYAN/HAMRICK  
 
ADDITIONAL 3-7 DAY HAZARDS INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS 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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