062  
FXUS02 KWBC 030700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT SAT NOV 03 2018  
 
VALID 12Z TUE NOV 06 2018 - 12Z SAT NOV 10 2018  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT
 
 
RECENT MODELS AND ENSEMBLES OFFER REASONABLY GOOD SOLUTION  
CLUSTERING DAYS 3-5, BUT DIFFERENCES AND RUN-RUN VARIANCE BECOMES  
PROBLEMATIC INTO DAYS 6/7 AT MID-SMALLER SCALES. ACCORDINGLY, THE  
WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A  
COMPOSITE MODEL AND ENSEMBLE BLEND DAYS 3-5 BEFORE QUICKLY  
TRANSITIONING TO MAINLY AN ENSEMBLE MEAN BLEND BY DAYS 6/7  
CONSISTENT WITH INCREASING FORECAST SPREAD/UNCERTAINTY.  
   
..PATTERN OVERVIEW/WEATHER THREATS
 
 
BROAD CYCLONIC FLOW/UPPER-LEVEL TROUGHING SPREADS OVER MUCH OF THE  
LOWER 48 NEXT WEEK BETWEEN UPPER RIDGES THAT HOLD OVER THE EASTERN  
PACIFIC AND WESTERN ATLANTIC. THE MEAN TROUGH WILL BE REINFORCED  
BY A SERIES OF SHORTWAVES ORIGINATING IN THE NORTH PACIFIC THAT  
POTENTIALLY INTERACT/AMPLIFY OVER THE PLAINS WITH ADDITION OF  
SHORTWAVE ENERGY OF POLAR/ARCTIC ORIGIN. THERE IS AMPLE THREAT FOR  
DEEPENING LOW PRESSURE TO LIFT INTO THE MIDWEST/GREAT LAKES BY  
TUESDAY TO TRACK OVER EASTERN CANADA MID-LATER WEEK. THIS  
WILL FORCE A PRECIPITATION FOCUSING FRONTAL SYSTEM ACROSS THE  
CENTRAL THEN EASTERN STATES. COLDER CANADIAN AIR TO DIG INTO LOWER  
48 IN THE WAKE OF SYSTEM PASSAGE SUPPORTS ORGANIZED SNOW ON THE  
NORTHWEST SYSTEM PERIPHERY, MAINLY OVER THE UPPER MIDWEST. STREAM  
PHASING/SEPARATION SPECIFICS ARE MUCH MORE UNCERTAIN LATER PERIOD  
AND INDIVIDUAL MODEL RUNS ARE VARIED WITH SUBSEQUENT SURFACE  
LOW/ORGANIZED PRECIPITATION DEVELOPMENT, BUT THE POTENTIAL AS  
ENERGY DIGS INTO THE MEAN TROUGH IS CERTAINLY THERE EVEN AS WPC  
PROGS CURRENTLY OFFER A MORE CONSERVATIVE DETERMINISTIC SOLUTION.  
 
IN THIS PATTERN MUCH OF THE EAST-CENTRAL U.S. WILL SEE WIDESPREAD  
PRECIPITATION EARLY-MIDWEEK AS DYNAMIC SUPPORT ALOFT COMBINES WITH  
INCREASINGLY FAVORAVBLE RETURN THETAE ADVECTION WITH STORM/FRONTAL  
ADVANCE AND DEEPENING. AN EXPANDING AREAS OF RAIN  
WILL SPREAD NORTHEASTWARD AHEAD OF THE SYSTEM. OVER THE EAST, A  
LINGERING FRONT MAY BRING LEAD POTENTIAL FOR PRECIPITATION BACK TO  
THE I-95 CORRIDOR FROM THE SOUTHEAST ALL THE WAY NORTHWARD TO NEW  
ENGLAND. LATER WEEK MORE MODEST PRECIPITATION MAY RENEW OVER THE  
S-CENTRAL/SOUTHERN U.S./GULF OF MEXICO AS ADDITIONAL SHORTWAVE  
ENERGIES DIG INTO THE BASE OF THE LONGWAVE TROUGH ALOFT AND FEED  
UPON MOISTURE POOLED ALONG A STALLED WAVY/TRAILING FRONT. THE  
EXTENT THAT A WAVE ALONG THIS FRONT WILL DEVELOP AND LIFT  
NORTHWARD OVER THE EAST-CENTRAL TO EASTERN U.S. FRI-NEXT SATURDAY  
IS UNCERTAIN.  
 
MEANWHILE, PERIODS OF MODERATE RAINS AND HIGHER ELEVATION SNOWS  
WILL BE POSSIBLE FOR THE PACIFIC NORTHWEST EARLY-LATER NEXT WEEK,  
WITH SNOWS SPREADING TO THE ROCKIES AS UPPER SHORTWAVES AND  
SURFACE FRONTS TRAVERSE THE REGION TO THE LEE OF THE EASTERN  
PACIFIC UPPER RIDGE.  
 
TEMPERATURES WILL BE BELOW AVERAGE FROM THE NORTHERN ROCKIES  
THROUGH THE PLAINS INTO THE GREAT LAKES AND OHIO VALLEY AS  
REINFORCING COLD FRONTS DRAG COOL/COLD CANADIAN AIR THROUGH THE  
REGION. THE WEST WILL SEE NEAR TO ABOVE AVERAGE TEMPERATURES  
THANKS TO UPPER RIDGING WHILE THE EAST WILL BE A BIT VARIABLE --  
WARMING UP AHEAD OF THE GREAT LAKES SYSTEM TUE/WED THEN COOLING  
OFF AFTER THE FRONT PASSES. SOME RECORDS HIGHS MAY BE POSSIBLE  
AHEAD OF THE FRONT ACROSS THE SOUTHEAST/FLORIDA TUE/WED.  
 
SCHICHTEL  
 
WPC MEDIUM RANGE 500 MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDEXES 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  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
 

 
 
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