204  
FXUS02 KWBC 090638  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
137 AM EST SAT FEB 09 2019  
 
VALID 12Z TUE FEB 12 2019 - 12Z SAT FEB 16 2019  
   
..OVERVIEW
 
 
A PERSISTENT UPPER RIDGE AXIS EXTENDING FROM THE NORTH PACIFIC  
ACROSS ALASKA WILL CONTINUE TO BE A DOMINANT INFLUENCE ON THE  
WEATHER PATTERN ACROSS THE CONUS. TELECONNECTIONS ASSOCIATED WITH  
THE STRONGEST POSITIVE HEIGHT ANOMALIES IN THE RIDGE SUPPORT A  
DOWNSTREAM POSITIVELY-TILTED MEAN TROUGH NEAR/OFF THE PACIFIC  
NORTHWEST AND ABOVE AVERAGE HEIGHTS FROM THE SOUTHERN PLAINS TO  
THE EASTERN SEABOARD ON THE NORTHENR PERIPHERY OF A RELATIVELY  
STRONG SUBTROPICAL RIDGE. A STRONG THERMAL GRADIENT IN BETWEEN  
THESE DOMINANT FEATURES, FROM THE CENTRAL PLAINS TO THE GREAT  
LAKES, WILL LARGELY DENOTE THE PREVAILING STORM TRACK THROUGH THE  
FORECAST PERIOD, WITH PACIFIC SHORTWAVE ENERGY SPAWNING  
INTENSIFYING SURFACE CYCLONES AS THEY REACH THE REGION OF  
INCREASED BAROCLINICITY AND BROAD CYCLONIC FLOW ACROSS THE CENTRAL  
U.S.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT AND PREFERENCES
 
 
MODELS CONTINUE TO VARY WITH RESPECT TO THE INTENSITY OF A  
SHORTWAVE/SURFACE CYCLONE INITIALLY ACROSS THE MIDWEST ON DAY 3  
(TUE), BUT MODEL/ENSEMBLE SOLUTIONS ARE QUITE WELL CLUSTERED ON  
THE TRACK OF THE SYSTEM AS IT MOVES INTO THE GREAT LAKES BY DAY 4  
(WED). THE SAME HOLDS TRUE FOR A TRIPLE POINT COASTAL LOW EXPECTED  
TO DEVELOP ALONG THE NEW ENGLAND COAST TUE NIGHT/WED MORNING.  
WHILE DETERMINISTIC SOLUTIONS SHOW SOME RELATIVELY SMALL TIMING  
DIFFERENCES, SOLUTIONS ARE GENERALLY WELL-CLUSTERED. FINALLY,  
SHORTWAVE ENERGY REACHING THE NORTHWEST TUE-WED HAS SHOWN IMPROVED  
CONSENSUS AMONG THE GUIDANCE RELATIVE TO THIS TIME LAST NIGHT.  
MODELS HAVE TRENDED TOWARD EJECTING THIS ENERGY INLAND WED AS  
OPPOSED TO KEEPING A MORE CONSOLIDATED/ELONGATED UPPER TROUGH JUST  
OFFSHORE (AS A SIGNIFICANT QUANTITY OF GUIDANCE WAS SUGGESTING  
THIS TIME LAST NIGHT). OVERALL, THE ECMWF (12Z FRI) AND GFS/FV3  
(18Z FRI) SOLUTIONS SHOWED THE BEST CONSENSUS ACROSS THE BOARD  
DURING DAYS 3-5, AND THUS THIS FORECAST FOR THIS TIME PERIOD WAS  
BASED ON A MULTI-MODEL BLEND OF THESE SOLUTIONS.  
 
BY THU THE AFORMENTIONED PACIFIC SHORTWAVE SHOULD BE CROSSING THE  
GREAT BASIN/ROCKIES, AND MODELS CONTINUE TO SHOW IMPROVED  
CONSENSUS. BY THE TIME THE ENERGY REACHES THE CENTRAL U.S. AND  
BEGINS TO INTENSIFY ALONG WITH THE SURFACE CYCLONE, DIFFERENCES  
EMERGE AMONG THE GUIDANCE, ESPECIALLY WITH RESPECT TO THE DEGREE  
OF DEEPENING AND ANY POTENTIAL INTERACTIONS WITH NORTHERN STREAM  
SHORTWAVE ENERGY. ENSEMBLE SCATTERPLOTS SHOW RATHER POOR  
CLUSTERING AMONG SOLUTIONS BY FRI AND CONTINUING INTO SAT AS THE  
SYSTEM REACHES THE GREAT LAKES. FARTHER WEST, MODELS AGREE THAT  
YET ANOTHER SHORTWAVE SHOULD REACH THE PACIFIC NORTHWEST LATE THU  
INTO FRI, WITH MOST SOLUTIONS SHOWING THE ENERGY SLOWLY SAGGING  
SOUTHWARD ALONG THE COAST THROUGH SAT. ENSEMBLE MEANS HAVE SHOWN A  
BIT MORE STABILITY FROM RUN TO RUN RELATIVE TO DETERMINISTIC  
GUIDANCE DURING DAYS 6-7 (FRI-SAT). THUS, MAJORITY WEIGHT WAS  
SHIFTED TOWARD THE ECENS/GEFS ENSEMBLE MEANS FOR THE FORECAST  
DURING THIS TIME PERIOD.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
THE LOW PRESSURE SYSTEM CROSSING THE MIDWEST/GREAT LAKES TUE-WED  
WILL BRING POTENTIALLY MODERATE TO HEAVY SNOWFALL TO AREAS NORTH  
OF THE LOW TRACK. A BROAD AREA OF OVERRUNNING MOISTURE NORTH OF  
THE WARM FRONT MAY ALSO BRING WINTRY PRECIPITATION TO PORTIONS OF  
THE MID-ATLANTIC AND NORTHEAST, WITH THE POTENTIAL FOR HEAVIER  
SNOW ACROSS PORTIONS OF NEW ENGLAND AS THE LOW DEVELOPS ALONG THE  
COAST TUE NIGHT/EARLY WED. THE SAME AREAS MAY SEE WINTER WEATHER  
POTENTIAL AGAIN THU-FRI AS THE NEXT LOW PRESSURE SYSTEM FOLLOWS A  
VERY SIMILAR TRACK EVOLUTION. MEANWHILE, THE MEAN TROUGH AXIS OFF  
THE WEST COAST WITH FREQUENT INCOMING SHORTWAVES WILL KEEP  
PRECIPITATION RATHER WIDESPREAD FROM CALIFORNIA TO THE PACIFIC  
NORTHWEST. EXPECT CONTINUED POTENTIAL FOR HEAVY MOUNTAIN SNOW AND  
LOWER ELEVATION RAIN. PERSISTENT COLD AIR NORTH OF AN ARCTIC  
FRONTAL BOUNDARY MAY ALSO BRING SNOWFALL POTENTIAL TO LOWER  
ELEVATIONS IN THE PACIFIC NORTHWEST.  
 
TEMPERATURES ARE FORECAST TO BE WELL BELOW AVERAGE FROM THE  
PACIFIC NORTHWEST TO THE NORTHERN HIGH PLAINS THROUGH THE FORECAST  
PERIOD, WITH TEMPERATURES 15 TO 30 DEG F BELOW AVERAGE ACROSS A  
BROAD AREA. FARTHER EAST, MANY AREAS WILL EXPERIENCE ABOVE AVERAGE  
TEMPERATURES. HIGH TEMPERATURES COULD REACH 10 TO 20 DEG F ABOVE  
AVERAGE ACROSS PORTIONS OF THE OHIO VALLEY AND SOUTHEAST TUE IN  
THE WARM SECTOR OF THE LOW PRESSURE SYSTEM. OTHERWISE, NEAR TO  
SLIGHLY ABOVE AVERAGE TEMPERATURES ARE EXPECTED TO PERSIST FROM  
THE SOUTHERN PLAINS TO THE SOUTHEAST/MID-ATLANTIC FROM WED ONWARD.  
 
RYAN  
 
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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