222  
FXUS02 KWBC 310659  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
158 AM EST THU JAN 31 2019  
 
VALID 12Z SUN FEB 3 2019 - 12Z THU FEB 7 2019  
   
..OVERVIEW
 
 
AFTER THE RECENT AMPLIFIED PATTERN ACROSS MUCH OF THE CONTINENTAL  
U.S. THIS WEEK, A RETURN TO A MORE QUASI-ZONAL FLOW PATTERN  
APPEARS LIKELY BY THE BEGINNING OF THE MEDIUM RANGE PERIOD THIS  
WEEKEND. THE STORM SYSTEM THAT WILL BE CROSSING THE DESERT  
SOUTHWEST LATE THIS WEEK SHOULD BE PRESENT AS AN OPEN WAVE ACROSS  
THE SOUTHEAST U.S. BY SUNDAY AS A SOUTHERN STREAM DISTURBANCE.  
THE PATTERN CHANGE CONTINUES GOING INTO THE FIRST PART OF NEXT  
WEEK AS THE LARGE SCALE PACIFIC TROUGH WORKS ITS WAY INLAND AND  
SUPPORTS SURFACE LOW DEVELOPMENT ACROSS THE GREAT PLAINS AND UPPER  
MIDWEST. THE RESPONSE TO THIS WILL LIKELY BE A BROAD UPPER TROUGH  
BECOMING ESTABLISHED OVER THE WESTERN U.S. BY TUESDAY WITH A  
WARMER WEATHER PATTERN FOR THE EASTERN U.S. BY THE END OF THE  
FORECAST PERIOD WEDNESDAY.  
 
   
..GUIDANCE EVALUATION/PREFERENCES
 
 
MODELS AND ENSEMBLE MEANS ARE IN RELATIVELY GOOD AGREEMENT ON  
SUNDAY WITH A COUPLE OF SHORTWAVE PERTURBATIONS OVER THE WESTERN  
U.S. AND A SOUTHERN STREAM SHORTWAVE ACROSS THE SOUTHEAST U.S.  
THE UKMET INDICATES LESS OF A SURFACE HIGH PRESSURE RIDGE BUILDING  
SOUTHWARD OUT OF CANADA AND SLOWER WITH THE PACIFIC DISTURBANCE  
APPROACHING CALIFORNIA ON MONDAY COMPARED TO THE MODEL CONSENSUS.  
THE CMC CONTINUES TO BE STRONGER WITH A SURFACE LOW DEVELOPING OFF  
THE SOUTHEAST COAST EARLY IN THE FORECAST PERIOD WHEREAS THE  
MAJORITY OF MODEL SOLUTIONS SUPPORT MORE OF AN INVERTED TROUGH  
FEATURE. MODEL AGREEMENT HAS IMPROVED WITH THE SURFACE LOW  
TRACKING ACROSS THE GREAT LAKES MONDAY NIGHT, ALTHOUGH THE ECMWF  
IS SLOWER WITH THE PASSAGE OF THE TRAILING COLD FRONT ACROSS THE  
PLAINS. BY WEDNESDAY, A SECOND SURFACE LOW IS PROGGED TO DEVELOP  
ALONG THIS SAME BOUNDARY AND LIKELY TRACK A BIT FARTHER TO THE  
SOUTHEAST ACROSS THE OHIO VALLEY REGION AND EVENTUALLY THE  
NORTHEAST U.S. BY THURSDAY, WITH THE EC MEAN PROVIDING A GOOD IDEA  
ON PLACEMENT FOR THE FRONT WITH THIS SYSTEM. ABOVE AVERAGE  
AGREEMENT EXISTS FOR THE CANADIAN HIGH PRESSURE SETTLING SOUTHWARD  
ACROSS THE NORTH-CENTRAL U.S. LATE IN THE FORECAST PERIOD. THE  
WPC FORECAST WAS BASED MAINLY ON A GFS/ECMWF BLEND WITH SOME UKMET  
ON SUNDAY, AND THEN MAINLY GFS/ECMWF WITH INCREASING USE OF THE  
ENSEMBLE MEANS TOWARDS THE END OF THE FORECAST PERIOD.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
A MUCH MILDER WEATHER PATTERN WILL BE PREVALENT ACROSS THE  
MAJORITY OF THE CENTRAL AND EASTERN U.S. BY THIS WEEKEND WITH HIGH  
TEMPERATURES RUNNING ABOUT 10 TO 20 DEGREES ABOVE CLIMATOLOGICAL  
AVERAGES, AND MILD OVERNIGHT LOWS ACROSS THE MIDWEST AND OHIO  
VALLEY AS FLOW FROM THE GULF OF MEXICO ADVECTS HIGHER HUMIDITY  
OVER THE REGION. A COUPLE OF WELL DEFINED LOW PRESSURE SYSTEMS  
ARE EXPECTED TO TRACK ACROSS THE GREAT PLAINS AND MIDWEST OVER THE  
COURSE OF THE MEDIUM RANGE PERIOD, WITH THE POTENTIAL FOR  
SIGNIFICANT SNOW TO THE NORTHWEST OF THE SURFACE LOWS THAT DEVELOP  
ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST, AND ARCTIC AIRMASSES  
WILL LIKELY SETTLE SOUTHWARD ACROSS THE DAKOTAS AND MONTANA.  
BASED ON CURRENT PROJECTIONS, THE SEVERITY OF THE COLD WILL BE  
LESS THAN THE ONGOING ARCTIC INTRUSION NOW.  
 
HEAVY RAIN AND MOUNTAIN SNOW IS EXPECTED ACROSS MUCH OF CALIFORNIA  
AND THE TERRAIN OF THE INTERMOUNTAIN WEST THIS WEEKEND AS A STRONG  
PACIFIC DISTURBANCE MOVES INLAND. SHOWERS AND STORMS ARE LIKELY  
TO DEVELOP FROM THE GULF COAST TO THE MIDWEST IN THE WARM SECTORS  
OF THE TWO SURFACE LOWS. SOME OF THIS RAINFALL MAY BE LOCALLY  
HEAVY, WITH THE HIGHEST LIKELIHOOD FOR THIS BECOMING REALIZED OVER  
THE SOUTHEAST U.S. FOR NEXT WEDNESDAY AND THURSDAY.  
 
HAMRICK/KONG  
 
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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