362  
FXUS02 KWBC 250700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT THU OCT 25 2018  
 
VALID 12Z SUN OCT 28 2018 - 12Z THU NOV 01 2018  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT AND PREFERENCES
 
 
AMPLIFIED FLOW WILL REMAIN FIXED OVER THE CONTINENTAL U.S.  
ACCOMPANIED BY BROAD LONGWAVE TROUGHING FROM THE MISSISSIPPI RIVER  
EASTWARD. WITHIN THIS NEGATIVE HEIGHT ANOMALY, A LEAD SHORTWAVE  
SHOULD BE IN THE PROCESS OF WEAKENING WHILE LIFTING THROUGH THE  
NEW ENGLAND COAST. IN ITS WAKE, SHARP HEIGHT FALLS ARE FORECAST TO  
SWEEP THROUGH THE MID-SOUTH ON SUNDAY NIGHT SPAWNING AN ADDITIONAL  
AREA OF LOW PRESSURE OVER THE DELMARVA PENINSULA BY THE FOLLOWING  
MORNING. MEAN TROUGHING WILL REMAIN OVER THE NORTHEASTERN U.S.  
UNTIL TUESDAY BEFORE MID-LEVEL SOUTHWESTERLY FLOW ENSUES AHEAD OF  
THE NEXT TROUGH TO CONCLUDE THE PERIOD. SHIFTING FOCUS TO UPSTREAM  
LOCATIONS, PROGRESSIVE MID-LATITUDE FLOW WILL USHER IN LOWERING  
HEIGHTS TOWARD THE PACIFIC NORTHWEST/BRITISH COLUMBIA COAST ON  
SUNDAY. A FULL-LATITUDE TROUGH SHOULD CONTINUE TO MAKES ITS WAY  
EASTWARD TOWARD THE CENTRAL U.S. BY MID-WEEK WHILE A CLOSED LOW  
MAY PINCH OFF OVER THE FOUR CORNERS REGION. BY DAY 7/NOVEMBER 1,  
THE ULTIMATE SYNOPTIC CONFIGURATION WILL FAVOR RIDGES OVER THE  
EASTERN PACIFIC AND WESTERN ATLANTIC WITH BROAD LONGWAVE TROUGHING  
SANDWICHED IN BETWEEN.  
 
REGARDING THE MODEL GUIDANCE, A GENERAL QUICKER TREND IS EVIDENT  
VIA MULTI-CYCLE ENSEMBLE SPAGHETTI PLOT COMPARISONS. REGARDING THE  
EVOLVING WAVE WITH THE SECONDARY HEIGHT FALLS TRACKING ACROSS THE  
MID-SOUTH, THERE ARE LESS SURFACE LOW STAMPS OVER THE DELMARVA  
PENINSULA REGION ON MONDAY MORNING SUGGESTING A DELAY IN SURFACE  
DEVELOPMENT. BY TUESDAY MORNING, MANY OPERATIONAL MODELS SUPPORT  
THE WAVE CROSSING VERY NEAR THE 40N/70W BENCHMARK, ALBEIT IN A  
SOMEWHAT FRACTURED STATE. IN ITS WAKE, GLOBAL MODELS AGREE ON  
ESTABLISHING HIGH PRESSURE OVER THE EASTERN U.S. BY MID-WEEK WHILE  
A SLOW MOVING FRONTAL ZONE TRACKS THROUGH THE CENTRAL STATES.  
INTERMITTENTLY SOLUTIONS WILL SHOW A MORE AMPED UP WAVE TRACKING  
ACROSS THE MIDDLE OF THE COUNTRY, MOST NOTABLY THE 12Z GFS.  
HOWEVER, THESE PARTICULAR SCENARIOS DO NOT SHOW UP VERY OFTEN AS  
THE BETTER FORCING IS EXPECTED TO STAY CLOSER TO THE INTERNATIONAL  
BORDER WITH CANADA. THERE IS DEFINITELY INCREASING CONFIDENCE OF  
AN UPPER LOW PINCHING OFF NEAR THE FOUR CORNERS WITH THIS TREND  
SHOWING UP A FEW RUNS AGO IN THE ECMWF ENSEMBLES. LOOKING BACK  
TOWARD THE EASTERN PACIFIC, STRONG ENSEMBLE CLUSTERING EXISTS WITH  
THE MEAN RIDGE SETTING UP INTO THE START OF NOVEMBER.  
 
THE FORECAST PREFERENCE WAS FOCUSED HEAVILY ON THE 18Z GFS/12Z  
ECMWF SOLUTIONS AS WELL AS THEIR ENSEMBLES (INCLUDING THE 12Z  
NAEFS MEAN). LINEARLY REDUCED OPERATIONAL COMPONENTS OF THE BLEND  
EACH DAY AS THE SPREAD INCREASED IN TIME. AND DID SELECT THE 18Z  
GFS CYCLE OVER ITS PREVIOUS RUN BECAUSE OF THE OVERLY DEVELOPED  
CENTRAL U.S. WAVE NEXT WEEK.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
REGARDING PRECIPITATION, THE MOST ACTIVE AREA WILL BE OVER THE  
PACIFIC NORTHWEST GIVEN THE SEMI-PERMANENT ONSHORE FLOW REGIME  
SETTING UP. THIS WILL OF COURSE BE AUGMENTED DURING THE PASSAGE OF  
ANY NOTABLE SHORTWAVES, ESPECIALLY THE ONE ARRIVING LATE THIS  
WEEKEND. SEVERAL INCHES OF RAINFALL ARE LIKELY ACROSS THE OLYMPICS  
AND CASCADES GIVEN FAVORABLE UPSLOPE TRAJECTORIES WITH SNOW  
EXPECTED OVER THE HIGHER ELEVATIONS EXTENDING INTO THE INTERIOR  
MOUNTAINOUS TERRAIN. ACROSS THE NORTHEASTERN U.S., IT WILL BE  
INTERMITTENTLY WET OVER THE REGION WITH SNOW POSSIBLE BACK OVER  
THE APPALACHIANS. A HEAVY STRIPE OF PRECIPITATION WILL BE EXITING  
NORTHERN MAINE ON SUNDAY MORNING AS A WAVE EXITS THE REGION WHILE  
BROAD CYCLONIC FLOW AND ADDITIONAL FORCING KEEPS SHOWERS IN THE  
PICTURE INTO EARLY NEXT WEEK. REGARDING THAT NEXT TROUGH CROSSING  
THE CENTRAL U.S. BY MID-WEEK, POLEWARD MOISTURE RETURN SHOULD  
ALLOW RAINFALL TO BREAK OUT ALONG THE SLOW-MOVING FRONTAL ZONE.  
WHILE LIKELY FOCUSING OVER THE ARKLATEX REGION, UNCERTAINTY  
REMAINS RATHER GREAT AND WILL BE DRIVEN BY WHERE INSTABILITY IS  
MORE PREVALENT.  
 
IN TERMS OF TEMPERATURES, IT SHOULD REMAIN COOL OVER LARGE  
SECTIONS OF THE EASTERN U.S. GIVEN THE LOWER HEIGHTS TRAVERSING  
THE REGION. FORECAST ANOMALIES SHOULD BE AROUND TO 10 TO 15  
DEGREES BELOW CLIMATOLOGY, PARTICULARLY OVER THE OHIO VALLEY INTO  
THE NORTHEASTERN U.S. THROUGH EARLY NEXT WEEK. EVENTUALLY NUMBERS  
SHOULD RETURN CLOSER TO AVERAGE FOR LATE OCTOBER GIVEN  
MID-SOUTHWESTERLY FLOW BECOMING ESTABLISHED. OUT TO THE WESTERN  
U.S., TEMPERATURES WILL BE AROUND 10 TO 15 DEGREES ABOVE AVERAGE,  
PARTICULARLY OVER THE CENTRAL GREAT BASIN INTO THE ROCKIES GIVEN  
THE RIDGING ALOFT. AS HEIGHTS LOWER FROM TUESDAY ONWARD, A COOL  
DOWN IS EXPECTED TO SHIFT EASTWARD TOWARD THE CENTRAL U.S. FOR  
MUCH OF NEXT WEEK.  
 
THIS WILL BE MY FINAL DISCUSSION AFTER 12 YEARS AT WPC (FORMERLY  
HPC). MY ADVENTURES WILL TAKE ME TO SACRAMENTO, CALIFORNIA WHERE I  
WILL BE WORKING AT THEIR LOCAL FORECAST OFFICE STARTING IN  
MID-NOVEMBER!  
 
RUBIN-OSTER  
 
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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