821  
FXUS02 KWBC 042026  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
325 PM EST MON MAR 04 2019  
 
VALID 12Z THU MAR 07 2019 - 12Z MON MAR 11 2019  
   
..WEATHER PATTERN OVERVIEW
 
 
EXPECT A FAIRLY PROGRESSIVE PATTERN ACROSS THE LOWER 48 WITH  
SYSTEMS EJECTING FROM A LONG-TERM EASTERN PACIFIC/WEST COAST MEAN  
TROUGH. A LEADING WEAK FEATURE MAY SPREAD SOME PRECIPITATION OVER  
PARTS OF THE CENTRAL/EASTERN STATES BUT WITH GREATER THAN AVERAGE  
UNCERTAINTY OVER COVERAGE AND AMOUNTS. FOLLOWING THIS WILL BE THE  
STRONGEST SYSTEM OF THE PERIOD, LIKELY MOVING INTO THE WEST BY FRI  
AND THEN TRACKING FROM THE CENTRAL HIGH PLAINS NORTHEASTWARD  
DURING THE WEEKEND. VARIOUS WEATHER THREATS WILL ACCOMPANY THIS  
STORM DURING ITS EXISTENCE. ANOTHER SYSTEM MAY APPROACH  
CALIFORNIA BY NEXT MON.  
 
   
..MODEL GUIDANCE EVALUATION AND PREFERENCES
 
 
EARLY IN THE PERIOD, THERE ARE ALREADY GUIDANCE DISCREPANCIES FOR  
THE STRENGTH OF THE WEAK WAVE CROSSING THE CENTRAL/EASTERN STATES.  
GFS RUNS ARE STRONGEST WITH THE SHORTWAVE ALOFT/SURFACE WAVE  
WHILE OTHER SOLUTIONS ARE WEAKER TO VARYING DEGREES, WITH  
CORRESPONDING EFFECTS ON PRECIPITATION COVERAGE/INTENSITY.  
RELATIVELY LOW PREDICTABILITY OF SUCH A SMALL SCALE FEATURE FAVORS  
AN INTERMEDIATE/BLENDED APPROACH.  
 
AT LEAST IN RELATIVE TERMS THERE IS DECENT CLUSTERING FOR THE  
SYSTEM REACHING THE WEST ON FRI AND TRACKING NORTHEASTWARD FROM  
THE PLAINS. TWO SIGNIFICANT UNKNOWNS WILL BE ITS INTERACTION WITH  
ENERGY WITHIN/AROUND THE UPPER LOW INITIALLY OVER VANCOUVER ISLAND  
AND THEN POSSIBLE INFLUENCE FROM SHORTWAVE ENERGY THAT MAY DROP  
SOUTHEASTWARD THROUGH CANADA. AS THE SYSTEM REACHES THE  
MIDWEST/NORTHWESTERN GREAT LAKES THE GFS IS ON THE STRONGER SIDE  
OF THE SPREAD AND COULD BE A LITTLE OVERDONE CONSIDERING IT HAS  
THE GREATEST INFLUENCE AMONG GUIDANCE OF THE CANADIAN SHORTWAVE  
ENERGY. HOWEVER IT SEEMS LIKELY THAT THE SYSTEM WILL BE STRONGER  
THAN AT LEAST THE ECMWF/CMC ENSEMBLE MEANS. THUS A MODEL/MEAN  
COMPROMISE PROVIDES A REASONABLE ACCOUNT FOR DETAIL AND  
UNCERTAINTY. BY LATE IN THE PERIOD THE MODELS/ENSEMBLES DEVELOP  
CONSIDERABLE SPREAD REGARDING THE AMPLITUDE OF UPPER TROUGHING  
REACHING THE EAST--GFS/GEFS MEMBERS THE MOST AMPLIFIED,  
ECMWF/ECMWF MEMBERS THE FLATTEST, AND CMC-BASED GUIDANCE  
IN-BETWEEN. THE MEAN TROUGHING NEAR THE WEST COAST SUGGESTS THAT  
THE EASTERN TROUGH SHOULD BE WEAKER THAN FORECAST BY THE GFS TO  
SOME DEGREE. AT THE SURFACE THERE IS A NOTABLE TREND IN THE GEFS  
MEAN TOWARD A MORE INLAND SURFACE LOW TRACK LATE IN THE PERIOD,  
TOWARD THE ECMWF MEAN.  
 
THE SYSTEM TRACKING TOWARD SOUTHERN CALIFORNIA BY DAY 7 MON SHOWS  
BETTER THAN AVERAGE AGREEMENT FOR A FORECAST THAT FAR OUT IN TIME.  
CURRENTLY A MODEL/ENSEMBLE MEAN COMPROMISE REPRESENTS CONSENSUS  
WELL. THE PRIMARY TREND OF NOTE OVER THE PAST 1-2 DAYS IS A  
FASTER ADJUSTMENT IN THE GEFS MEAN.  
 
GIVEN A GENERAL PREFERENCE FOR A BLEND/INTERMEDIATE APPROACH, THE  
UPDATED FORECAST STARTED WITH COMPONENTS OF THE 06Z GFS AND 00Z  
ECMWF/UKMET/CMC DAYS 3-4 THU-FRI. THE FORECAST REMOVED THE UKMET  
AFTER FRI DUE TO STRAYING FROM CONSENSUS OVER SOME AREAS WHILE  
INTRODUCING SOME INPUT FROM THE 06Z GEFS/00Z ECMWF MEANS, WITH A  
MODEL/MEAN BLEND CONTINUING THROUGH DAY 7.  
 
   
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
 
 
OVER THE WEST EXPECT SIGNIFICANT SNOWFALL FROM THE SIERRA NEVADA  
THROUGH THE INTERMOUNTAIN WEST AND ROCKIES LATE THIS WEEK WITH A  
COMBINATION OF ONGOING ACTIVITY AND THE SYSTEM TRACKING INTO THE  
WEST BY FRI. SOME RAIN WILL BE POSSIBLE OVER COASTAL/LOW  
ELEVATION AREAS. PRECIPITATION WILL BECOME LIGHTER AND MORE  
SCATTERED DURING THE WEEKEND. THE SOUTHERN HALF OF CALIFORNIA MAY  
SEE AN INCREASE OF MOISTURE ON MON WITH THE APPROACH OF ANOTHER  
SYSTEM.  
 
THE LATE WEEK SYSTEM EMERGING FROM THE WEST WILL LIKELY INTENSIFY  
AS IT TRACKS FROM THE CENTRAL HIGH PLAINS NORTHEASTWARD DURING THE  
WEEKEND. THE NORTHERN PLAINS REGION HAS THE HIGHEST POTENTIAL FOR  
SIGNIFICANT SNOWFALL AT THIS TIME WITH AREAS FARTHER EAST INTO THE  
UPPER GREAT LAKES MORE SENSITIVE TO EXACT STORM TRACK. WINDS  
COULD BECOME STRONG ENOUGH TO PRODUCE BLIZZARD CONDITIONS  
DEPENDING ON HOW INTENSE THE SYSTEM BECOMES. MEANWHILE STRONG LOW  
LEVEL GULF INFLOW AHEAD OF THE ADVANCING STRONG COLD FRONT WILL  
SPREAD WIDESPREAD RAIN WILL DEVELOP FROM THE GULF COAST TO THE  
OHIO VALLEY AND SOUTHERN APPALACHIANS. THE BEST SIGNAL FOR  
HEAVIEST RAINFALL EXTENDS ACROSS THE SOUTH-CENTRAL MISSISSIPPI  
VALLEY AND TENNESSEE RIVER VALLEY WITH SIGNIFICANT AMOUNTS ALSO  
POSSIBLE OVER OTHER PARTS OF THE EAST. THIS RAINFALL COMBINED  
WITH ALREADY WET GROUND MAY POSE SOME FLOODING ISSUES.  
STRONG/SEVERE CONVECTION WILL BE ANOTHER THREAT THAT WILL NEED TO  
BE MONITORED. CONSULT STORM PREDICTION CENTER PRODUCTS FOR THE  
LATEST INFORMATION AS SPECIFICS BECOME MORE CLEAR.  
 
DURING THU-FRI A WEAK SYSTEM MAY SPREAD SOME PRECIPITATION ACROSS  
PARTS OF THE CENTRAL/EASTERN STATES (SNOW NORTH/RAIN SOUTH) BUT  
WITH LOW CONFIDENCE IN COVERAGE AND AMOUNTS. THEN BY THE START OF  
NEXT WEEK THERE IS ALSO SIGNIFICANT UNCERTAINTY OVER PRECIPITATION  
COVERAGE/AMOUNTS ACROSS PARTS OF THE SOUTHERN TIER, DEPENDING ON  
AMPLITUDE OF FLOW ALOFT OVER THE EAST.  
 
THE NORTHERN-CENTRAL PLAINS WILL LIKELY CONTINUE TO SEE BELOW  
NORMAL TEMPERATURES MOST DAYS WITH HIGHS TENDING TO BE 10-20F  
BELOW NORMAL WITH LOCALLY MORE EXTREME ANOMALIES ONE OR MORE DAYS.  
THE WEST WILL TEND TO SEE BELOW NORMAL HIGHS FOR MUCH OF THE  
PERIOD BUT MORNING LOWS SHOULD BE ABOVE NORMAL LATE THIS WEEK.  
THE SOUTH/EAST WILL SEE A BRIEF SURGE OF WARMTH AHEAD OF THE FRONT  
ASSOCIATED WITH THE PLAINS/GREAT LAKES STORM DURING THE WEEKEND.  
 
RAUSCH  
 
ADDITIONAL 3-7 DAY HAZARDS INFORMATION CAN BE FOUND ON THE WPC  
MEDIUM RANGE HAZARDS CHART AT:  
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP  
 
HAZARDS:  
- HEAVY PRECIPITATION ACROSS PORTIONS OF CALIFORNIA, MON, MAR 11.  
- HEAVY PRECIPITATION ACROSS PORTIONS OF THE MID-ATLANTIC, THE  
NORTHEAST, AND THE GREAT LAKES, SUN, MAR 10.  
- HEAVY RAIN ACROSS PORTIONS OF THE CENTRAL PLAINS, THE LOWER  
MISSISSIPPI VALLEY, THE TENNESSEE VALLEY, THE GREAT LAKES, THE  
MIDDLE MISSISSIPPI VALLEY, THE MID-ATLANTIC, THE SOUTHERN  
APPALACHIANS, THE UPPER MISSISSIPPI VALLEY, THE SOUTHEAST, THE  
SOUTHERN PLAINS, AND THE OHIO VALLEY, SAT-SUN, MAR 9-MAR 10.  
- HEAVY RAIN ACROSS PORTIONS OF THE MID-ATLANTIC, THE NORTHEAST,  
AND THE CENTRAL APPALACHIANS, SUN-MON, MAR 10-MAR 11.  
- HEAVY RAIN ACROSS PORTIONS OF THE SOUTHWEST, MON, MAR 11.  
- HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL GREAT BASIN,  
CALIFORNIA, AND THE SOUTHWEST, THU-FRI, MAR 7-MAR 8.  
- HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE  
MISSISSIPPI VALLEY, THE GREAT LAKES, THE UPPER MISSISSIPPI VALLEY,  
AND THE NORTHERN PLAINS, SAT-SUN, MAR 9-MAR 10.  
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE LOWER  
MISSISSIPPI VALLEY, THE TENNESSEE VALLEY, THE MIDDLE MISSISSIPPI  
VALLEY, THE MID-ATLANTIC, THE SOUTHEAST, AND THE OHIO VALLEY.  
- FLOODING LIKELY ACROSS PORTIONS OF THE CENTRAL PLAINS AND THE  
SOUTHEAST.  
- MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE CENTRAL  
PLAINS, THE MIDDLE MISSISSIPPI VALLEY, THE SOUTHERN PLAINS, THE  
UPPER MISSISSIPPI VALLEY, AND THE NORTHERN PLAINS, THU-MON, MAR  
7-MAR 11.  
- MUCH BELOW NORMAL TEMPERATURES ACROSS PORTIONS OF THE NORTHEAST,  
THE CENTRAL APPALACHIANS, THE MID-ATLANTIC, THE SOUTHERN  
APPALACHIANS, THE GREAT LAKES, AND THE OHIO VALLEY, THU-FRI, MAR  
7-MAR 8.  
- ENHANCED WILDFIRE RISK ACROSS PORTIONS OF THE THE SOUTHERN  
ROCKIES, THE SOUTHERN PLAINS, AND THE SOUTHWEST, THU, MAR 7.  
 
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,  
QUANTITATIVE PRECIPITATION, WINTER WEATHER OUTLOOK PROBABILITIES  
AND HEAT INDICES ARE 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  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page