231  
FXUS02 KWBC 290659  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
158 AM EST TUE JAN 29 2019  
 
VALID 12Z FRI FEB 01 2019 - 12Z TUE FEB 05 2019  
   
..OVERVIEW
 
 
THE DEPARTURE OF A DEEP UPPER LEVEL VORTEX OVER QUEBEC AT THE  
BEGINNING OF THE FORECAST PERIOD THURSDAY AND GRADUAL WEAKENING OF  
MEAN TROUGHING ALOFT OVER THE EASTERN U.S. LATE THIS WEEK AND THE  
WEEKEND WILL PROMOTE A SIGNIFICANT WARMING TREND OVER THE EASTERN  
U.S. AT THE SAME TIME THE SHORT-RANGE WEST COAST MEAN RIDGE ALOFT  
WILL GIVE WAY TO A SERIES OF PACIFIC SYSTEMS THAT WILL BRING A  
RETURN OF SIGNIFICANT PRECIPITATION TO PARTS OF THE WEST WITH  
MOISTURE THAT WILL THEN SPREAD FARTHER EASTWARD. BY THE LATTER  
HALF OF THE PERIOD, THE SYNOPTIC SCALE PATTERN SHOULD EVOLVE  
TOWARD A POSITIVELY TILTED MEAN TROUGH OVER THE WEST AND POSITIVE  
HEIGHT ANOMALIES WITH SOME DEGREE OF RIDGING OVER THE EAST.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
MODELS AND ENSEMBLE MEANS ARE IN RELATIVELY GOOD AGREEMENT AT THE  
BEGINNING OF THE FORECAST PERIOD ON FRIDAY WITH RESPECT TO THE  
SYNOPTIC SCALE PATTERN. BY DAY 4 ON SATURDAY, SPEED AND AMPLITUDE  
DIFFERENCES ARE APPARENT WITH THE LARGE SCALE TROUGH NEAR  
CALIFORNIA. THE 18Z FV3 GFS IS NOT QUITE AS AMPLIFIED AS THE  
OPERATIONAL GFS, AND CLOSER TO THE ECMWF AND EC MEAN SOLUTIONS,  
AND THIS REMAINS THE CASE GOING INTO SUNDAY AS THE DISTURBANCE  
APPROACHES THE PLAINS. WITH THAT CONSIDERATION IN MIND, THE WPC  
FORECAST FAVORED THE SLOWER SET OF SOLUTIONS FOR THIS REGION, BUT  
NOT TO THE DEGREE INDICATED BY THE UKMET GIVEN ITS LACK OF  
ENSEMBLE SUPPORT.  
 
IN THE NORTHERN STREAM, A NUMBER OF SOLUTIONS SUGGEST  
AMPLIFICATION OF A SHORTWAVE ACROSS THE CANADIAN PRAIRIES NEXT  
WEEKEND, WITH AN ASSOCIATED SURFACE LOW PASSING ALONG THE  
U.S./CANADA BORDER TOWARD THE GREAT LAKES. MODEL CONSENSUS WAS A  
BIT BETTER HERE AND ENSEMBLE MEMBERS SHOWED REASONABLE CLUSTERING  
WITH RESPECT TO THE SURFACE LOW TRACK, EVEN WITH SOME  
TIMING/INTENSITY VARIABILITY EVIDENT IN DETERMINISTIC SOLUTIONS.  
GIVEN THESE CONSIDERATIONS, THE FORECAST DURING THE SECOND HALF OF  
THE FORECAST PERIOD CONTINUED TO EMPHASIZE THE ECMWF/FV3 GFS WITH  
INCREASING USE OF THE ENSEMBLE MEANS BY LATE IN THE FORECAST  
PERIOD.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
A PRONOUNCED MODERATING TREND IS EXPECTED BY THIS WEEKEND AFTER  
THE RECORD SETTING COLD TEMPERATURES MID-WEEK ACROSS THE  
NORTH-CENTRAL STATES. IT WILL STILL BE VERY COLD FROM THE UPPER  
MIDWEST TO NEW ENGLAND ON FRIDAY, WITH DEPARTURES ON THE ORDER OF  
10 TO 20 DEGREES BELOW NORMAL FOR LATE JANUARY. THE COLD  
TEMPERATURES LINGER ACROSS THE NORTHEAST U.S. ON SATURDAY WHILST  
MODERATING SIGNIFICANTLY FROM THE OHIO VALLEY TO THE GREAT PLAINS.  
THE MAJORITY OF THE EASTERN U.S. SHOULD BE ABOVE NORMAL BY SUNDAY  
WITH LOCATIONS FROM TEXAS TO THE OHIO VALLEY ABOUT 10-15 DEGREES  
ABOVE NORMAL OWING TO THE BORAD UPPER LEVEL RIDGE AND WARMER  
SOUTHERLY FLOW. BY EARLY NEXT WEEK, THE NEXT SURGE OF ARCTIC AIR  
SURGES SOUTH ACROSS THE NORTHERN PLAINS, WITH INDICATIONS THAT IT  
WILL NOT BE THE SAME MAGNITUDE AS THE ONGOING ARCTIC INTRUSION.  
 
MULTIPLE PACIFIC SYSTEMS WILL WIDESPREAD VALLEY RAIN AND MOUNTAIN  
SNOW TO A LARGE PORTION OF THE WEST BY FRIDAY AND THEN TO MUCH OF  
THE INTERMOUNTAIN WEST AND THE ROCKIES FOR THE WEEKEND. THE  
WEEKEND STORM SYSTEM WILL FIRST SPREAD RAIN/SNOW ACROSS THE  
NORTHWEST AND GRADUALLY MOVE SOUTH/SOUTHEAST. THE HEAVIEST QPF IS  
EXPECTED OVER FAVORED TERRAIN IN CALIFORNIA, ARIZONA, AND SOUTHERN  
UTAH. DURING THE LATTER HALF OF THE PERIOD, A SURFACE LOW IS  
FORECAST TO DEVELOP ACROSS THE CENTRAL PLAINS, AND THIS MAY  
PRODUCE A BAND OF SIGNIFICANT SNOW FROM NEBRASKA TO THE UPPER  
MIDWEST AND RAIN IN THE WARM SECTOR. SHOWERS AND STORMS ARE  
LIKELY ACROSS THE GULF COAST REGION AS MOISTURE INCREASES ACROSS  
THIS REGION.  
 
HAMRICK  
 
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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