836  
FXUS02 KWBC 021915  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
315 PM EDT SAT NOV 2 2024  
 
VALID 12Z TUE NOV 05 2024 - 12Z SAT NOV 09 2024  
   
..OVERVIEW  
 
THE MAJORITY OF GUIDANCE SHOWS STRONG UPPER RIDGING OVER PARTS OF  
THE SOUTHEASTERN U.S. AND WESTERN ATLANTIC WHILE STRONGLY DIGGING  
WESTERN U.S. TROUGH ENERGY LIKELY CLOSES OFF A LOW THAT DRIFTS OVER  
THE FOUR CORNERS BEFORE EMERGING INTO THE PLAINS BY LATE WEEK OR  
EARLY WEEKEND. THE UPPER LOW SHOULD PRODUCE AN AREA OF POTENTIALLY  
SIGNIFICANT SNOWFALL OVER PARTS OF THE ROCKIES AROUND MIDWEEK AND  
THEN SPREAD RAIN OVER THE PLAINS LATER IN THE WEEK. TO THE SOUTH OF  
THE UPPER RIDGE, GUIDANCE CONTINUES TO SHOW POSSIBLE CARIBBEAN  
INTO GULF OF MEXICO TROPICAL DEVELOPMENT (BEING MONITORED BY THE  
NATIONAL HURRICANE CENTER) WITH A LOT OF GUIDANCE SPREAD FOR WHERE  
THE SURFACE SYSTEM ITSELF MAY TRACK, AS WELL AS FOR THE PATH OF  
MOISTURE TO ITS NORTH/EAST. A WAVY FRONT PUSHING INTO THE  
MISSISSIPPI VALLEY BY TUESDAY MAY PRODUCE SOME ENHANCED RAINFALL  
OVER THAT REGION. NORTHERN STREAM FLOW WILL SEE MODERATE  
PROGRESSION, WITH A RIDGE BUILDING INTO WESTERN CANADA AND MEAN  
TROUGHING SETTING UP FARTHER EAST. A PACIFIC TROUGH MAY APPROACH  
THE NORTHWEST BY NEXT SATURDAY.  
   
..GUIDANCE/PREDICTABILITY ASSESSMENT  
 
UPDATED 00Z/06Z GUIDANCE IS IN GOOD AGREEMENT DURING THE EARLY  
PART OF THE MEDIUM-RANGE PERIOD (TUESDAY NOV 5 - SATURDAY NOV 9),  
DEPICTING A LEAD SOUTHERN STREAM WAVE LIFTING NORTHWARD AHEAD OF A  
BROAD AREA OF HIGH PRESSURE OVER THE EAST COAST WHILE MEAN  
TROUGHING REMAINS OVER THE WEST IN AN AMPLIFIED PATTERN. THIS WILL  
LEAD TO A WEAKENING WAVY FRONTAL BOUNDARY THROUGH THE  
MIDWEST/MISSISSIPPI VALLEY AS THE LEAD ENERGY LIFTS NORTHWARD AHEAD  
OF ADDITIONAL ENERGIES FROM THE WEST. GUIDANCE DIFFERS ON THE  
TIMING OF NORTHERN STREAM SHORTWAVES AND ACCOMPANYING FRONTAL  
SYSTEMS IN THE MID- TO LATE PERIOD ALONG THE NORTHERN TIER OF THE  
COUNTRY, THOUGH WITH LITTLE APPARENT IMPACTS ON SENSIBLE WEATHER.  
ATTENTION TURNS WEST AS A SHORTWAVE HELPS REINFORCE MEAN TROUGHING,  
WITH ALL THE DETERMINISTIC GUIDANCE AND GEFS/ECENS MEANS DEPICTING  
THE DEVELOPMENT OF A CLOSED LOW OVER THE SOUTHWEST. EASTWARD  
PROGRESSION OF THE LOW IS FASTEST IN THE UKMET FOLLOWED BY THE GFS.  
THE ECMWF IS THE SLOWEST WITH THE CMC MOST SIMILAR. THE ECENS MEAN  
AND GEFS MEAN GENERALLY FOLLOW THEIR RESPECTIVE DETERMINISTIC  
COUNTERPARTS. THE EC AI SUITE OF MODELS SHOW VARIOUS SOLUTIONS  
WITHIN THE RANGE OF GUIDANCE, INDICATING INCREASING UNCERTAINTY  
DURING THIS TIMEFRAME. THE 12Z GFS CAME IN AHEAD OF THE ECMWF/CMC  
SIMILAR TO THE 06Z RUN.  
 
EYES WILL ALSO BE ON THE TROPICS AS THE NATIONAL HURRICANE CENTER  
MONITORS A SYSTEM IN THE SOUTHWESTERN CARIBBEAN, CURRENTLY  
INDICATING AN 80% CHANCE OF TROPICAL SYSTEM FORMATION IN THE NEXT 7  
DAYS. THE GFS/ECMWF AS WELL AS THE ENSEMBLE MEANS INDICATE AN AREA  
OF LOW PRESSURE LIFTING NORTHWARD TOWARDS THE EASTERN GULF OF  
MEXICO BEFORE TAKING VARIOUS PATHS FURTHER NORTH OR WEST, WITH THE  
GFS FURTHER TO THE NORTH AND INTO THE CENTRAL GULF AND THE ECMWF TO  
THE WEST. THE GFS PATH IS FURTHER EAST COMPARED TO PRIOR RUNS. THE  
CMC HAS BEEN AN OUTLIER WITH A MUCH FASTER, EASTERN PATH THROUGH  
THE GULF AND INTO THE SOUTHEASTERN U.S. THE UPDATED NHC/WPC  
COORDINATED FORECAST BRINGS AN AREA OF LOW PRESSURE INTO THE GULF  
JUST TO THE WEST OF THE GFS PATH, SHOWING A MORE EASTWARD TREND  
THAN THE PRIOR FORECAST BUT STILL INCORPORATING THE POTENTIAL FOR  
MORE WESTWARD MOVEMENT AS INDICATED BY THE ECMWF.  
 
THE UPDATED WPC FORECAST USES A COMPOSITE BLEND OF THE  
DETERMINISTIC GUIDANCE WITH GOOD OVERALL AGREEMENT IN THE EARLY  
PERIOD. THE UKMET IS REMOVED IN THE MID-PERIOD GIVEN ITS MUCH  
FASTER PROGRESSION OF THE SOUTHWESTERN CLOSED LOW, AND THE CMC IS  
REMOVED GIVEN THE MORE AGGRESSIVE NORTHEASTWARD TRACK OF THE  
CARIBBEAN LOW PRESSURE SYSTEM. THE ECMWF IS EMPHASIZED OVER THE GFS  
FOR THE END OF THE PERIOD FAVORING MORE DETAIL OF THE WESTERN  
POSITION OF THE CLOSED LOW GIVEN SOME AGREEMENT FROM THE CMC IN  
THIS AREA, WITH A CONTRIBUTION FROM BOTH THE GEFS/ECENS MEANS TO  
HELP ACCOUNT FOR THE INCREASING UNCERTAINTY.  
 
THE QPF FORECAST REMAINS MORE DIFFICULT, WITH NOTABLY HIGH  
UNCERTAINTY FOR POTENTIAL RAINFALL OVER FLORIDA AND THE  
SOUTHEASTERN U.S. AS MOISTURE INCREASES AHEAD OF THE APPROACHING  
LOW, INCLUDING HIGH SPATIAL DISPARITY WITH THE ENSEMBLE MEANS.  
FAVORED THE NBM WHICH INDICATES HIGHER RAINFALL OVER CENTRAL/SOUTH  
FLORIDA, THOUGH WITH AMOUNTS MODERATED A BIT FOR NOW GIVEN THE  
UNCERTAINTY. LATER IN THE FORECAST TOWARD THE END OF THE WEEK,  
HIGHER RAINFALL AMOUNTS ARE INDICATED WITH MORE MODERATE SPATIAL  
DIFFERENCES LATE THURSDAY/EARLY FRIDAY AS THE CLOSED LOW OVER THE  
SOUTHWEST BEGINS TO EMERGE OVER THE PLAINS. SPATIAL DIFFERENCES  
INCREASE ONCE AGAIN LATER FRIDAY/EARLY SATURDAY WITH THE GFS  
FAVORING A FASTER NORTHEASTWARD PROGRESSION TOWARDS THE MIDWEST  
WHILE THE ECMWF FAVORS AREAS FURTHER WEST OVER THE PLAINS. THE  
DETERMINISTIC GUIDANCE WAS USED TO INCREASE TOTALS GIVEN THE SIGNAL  
FOR HEAVIER PRECIPITATION THROUGH EARLY FRIDAY BEFORE SWITCHING TO  
HIGHER CONTRIBUTIONS FROM THE MEANS GIVEN THE SPATIAL DISPARITY.  
 
   
..WEATHER/HAZARDS HIGHLIGHTS  
 
 
A SLOW WAVY FRONT SHOULD APPROACH/REACH THE MISSISSIPPI VALLEY AND  
WESTERN GULF COAST BY TUESDAY-TUESDAY NIGHT, WITH CONTINUED  
POTENTIAL FOR SOME TRAINING OF MODERATE TO HEAVY RAINFALL BUT  
LIKELY TO A LESS PRONOUNCED DEGREE THAN EXPECTED JUST TO THE WEST  
IN THE SHORT RANGE. THE DAY 4 EXCESSIVE RAINFALL OUTLOOK MAINTAINS  
A MARGINAL RISK AREA FROM THE LOWER OHIO VALLEY SOUTHWESTWARD, NOW  
EXTENDING TO THE NORTHERN HALF OF THE TEXAS COAST. THERE HAS BEEN  
SOME IMPROVEMENT FOR GUIDANCE CLUSTERING REGARDING WHERE THE  
RELATIVE MAXIMUM OF RAINFALL SHOULD BE WITHIN THIS REGION (ALONG  
AND JUST EAST OF AN AREA FROM EASTERN ARKANSAS INTO FAR SOUTHERN  
ILLINOIS). HOWEVER GROUND CONDITIONS ARE GENERALLY NEUTRAL TO DRY  
AND THE GFS/ECMWF DO NOT SUGGEST TOO MUCH INSTABILITY REACHING THAT  
FAR NORTH. THUS FOR NOW WILL MAINTAIN JUST THE MARGINAL RISK AREA  
WHILE MONITORING FOR SIGNALS OF ANY HEAVIER BANDS THAT COULD FAVOR  
AN UPGRADE.  
 
ESPECIALLY BY WEDNESDAY, GUIDANCE DIVERGES CONSIDERABLY REGARDING  
THE DETAILS OF ANOMALOUS MOISTURE/HEAVIER RAINFALL THAT MAY  
OVERSPREAD PARTS OF THE SOUTHEAST/FLORIDA TO THE NORTH OF THE  
POSSIBLE CARIBBEAN INTO GULF TROPICAL DEVELOPMENT. THIS WILL DEPEND  
ON FINER SCALE DETAILS OF UPPER RIDGING WHOSE WESTERN SIDE WILL  
DETERMINE HOW MUCH MOISTURE/SHORTWAVE ENERGY MAY LIFT NORTHWARD.  
THE MOST COMMON THEME IS FOR SIGNIFICANT PRECIPITABLE WATER  
ANOMALIES TO REACH PORTIONS OF THE FLORIDA PENINSULA AT THE VERY  
LEAST, SO THE DAY 5 ERO STARTS OUT WITH A MARGINAL RISK AREA OVER  
THE SOUTHERN TWO-THIRDS OF FLORIDA. OTHER PARTS OF THE SOUTHEAST  
MAY ULTIMATELY BE INCLUDED DEPENDING ON GUIDANCE TRENDS. GUIDANCE  
SPREAD FOR WHAT HAPPENS WITH THIS MOISTURE AND THE POSSIBLE GULF  
FEATURE AFTER THURSDAY IS STILL VERY WIDE, KEEPING CONFIDENCE LOW.  
 
UPPER TROUGH DYNAMICS LIKELY CLOSING OFF AN UPPER LOW AROUND THE  
FOUR CORNERS SHOULD PUSH AN AREA OF MOUNTAIN SNOW SOUTHWARD THROUGH  
THE ROCKIES, WITH HIGHEST TOTALS LIKELY TO BE OVER SOUTHERN  
COLORADO/NORTHERN NEW MEXICO BASED ON THE CURRENT FORECAST PATH OF  
THE UPPER LOW. GUIDANCE TRENDS HAVE INDICATED MORE CONFIDENCE THAT  
SOME SNOW COULD ALSO OCCUR OVER PORTIONS OF THE HIGH PLAINS. EXPECT  
RAINFALL OVER THE PLAINS TO INCREASE IN COVERAGE AND INTENSITY  
AFTER MIDWEEK AS THE FOUR CORNERS UPPER LOW BEGINS TO DRIFT  
EASTWARD. THERE IS STILL UNCERTAINTY FOR THE DETAILS, BUT GRADUALLY  
INCREASING CONFIDENCE IN SOME AREAS OF HEAVIER RAINFALL.  
 
A LARGE PORTION OF THE EASTERN U.S. WILL SEE WELL ABOVE NORMAL  
TEMPERATURES, ESPECIALLY FROM TUESDAY INTO THURSDAY MORNING WHEN  
SOME AREAS WILL SEE PLUS 20F OR GREATER ANOMALIES (MORE FOR MORNING  
LOWS VERSUS DAYTIME HIGHS) ALONG WITH POTENTIAL FOR DAILY RECORDS  
FOR HIGHS/WARM LOWS. FRONTAL PROGRESSION WILL TEMPER THE MOST  
EXTREME ANOMALIES BUT PERSISTENT SOUTHEAST UPPER RIDGING SHOULD  
KEEP THE SOUTHERN TWO-THIRDS OF THE EAST ABOVE NORMAL THROUGH  
FRIDAY-SATURDAY. IN CONTRAST, THE UPPER TROUGH/LOW LIKELY AFFECTING  
THE WEST/ROCKIES FOR MULTIPLE DAYS SHOULD PRODUCE CHILLY  
TEMPERATURES FOR MOST OF NEXT WEEK WITH HIGHS OF 10-20F BELOW  
NORMAL MOST COMMON WEDNESDAY-FRIDAY.  
 
PUTNAM/RAUSCH  
 
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC MEDIUM  
RANGE HAZARDS OUTLOOK CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHPSCHICHTEL/HAMRICK  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL  
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT  
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:  
 
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/#PAGE=ERO  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW  
 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.
The Nexlab HPC Page
Main Text Page