063  
FXUS02 KWBC 151510  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1009 AM EST FRI FEB 15 2019  
 
VALID 12Z MON FEB 18 2019 - 12Z FRI FEB 22 2019  
 
...MULTI-DAY HEAVY RAIN THREAT FOR THE SOUTHEAST AND  
SOUTHERN/CENTRAL APPALACHIANS...  
 
...OVERVIEW AND GUIDANCE/PREDICTABILITY ASSESSMENT AND  
PREFERENCES...  
 
THE MODELS AND ENSEMBLES CONTINUE TO SHOW A PATTERN WHERE  
WAVES/UPPER TROUGHS PROGRESS OVER THE TOP OF THE NORTHEAST PACIFIC  
RIDGE AND REINFORCE THE PERSISTENT WESTERN US TROUGH. DEEP LAYER  
SOUTHWEST FLOW OVER THE EAST REINFORCES THE SOUTHEAST RIDGE, WITH  
THE MAJORITY OF MODELS/ENSEMBLES SHOWING A STRONG/PERSISTENT  
ANTICYCLONE OFF THE SOUTHEAST COAST WITH HEIGHTS NEAR 2 STANDARD  
DEVIATIONS ABOVE NORMAL. THIS PATTERN FAVORS WET CONDITIONS IN  
THE SOUTHEAST US AND AS DISCUSSED BELOW, POTENTIAL REMAINS HIGH  
FOR WAVES OF HEAVY RAIN IN PORTIONS OF THE SOUTHEAST US.  
 
THE 00Z ECMWF/CANADIAN/00Z ECMWF ENSEMBLE MEAN/06 UTC GFS/GEFS  
WERE EQUALLY WEIGHTED DAYS 3-6 FOR MON-THU. MODELS SHOW A FRONTAL  
WAVE CROSSING THE EASTERN U.S. DURING THAT TIME FRAME, WITH  
VARIATIONS AS TO HOW QUICKLY ENERGY TRANSFERS FROM A LOW OVER THE  
SOUTHERN/CENTRAL APPALACHIANS TO A SECOND LOW OFF THE MID-ATLANTIC  
COAST.  
 
TOWARDS THE END OF NEXT THU (DAY 6) THROUGH FRI 22 FEB (DAY 7),  
GUIDANCE CONTINUES TO SHOW RELATIVELY GOOD AGREEMENT WITH THE BIG  
PICTURE, BUT DIFFERENCES DEVELOP REGARDING HOW QUICKLY A SPOT OR  
CLOSED LOW IN THE SOUTHWEST US EJECTS TO THE EAST/NORTHEAST. THE  
FORECASTS SWITCHED TO GIVE LESS WEIGHT TO THE SLIGHTLY MORE  
PROGRESSIVE GFS AND MORE WEIGHT TO THE 00Z ECMWF ENSEMBLE MEAN AND  
06Z GEFS MEAN.  
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
MULTIPLE WAVES TRAVERSING THE SOUTHEAST FRONT COMBINE WITH THE  
ENHANCED PRECIPITABLE WATER AND LIFT TO BRING SEVERAL ROUNDS OF  
WIDESPREAD AND LIKELY HEAVY RAIN. MODEL/ENSEMBLE GUIDANCE SHOW THE  
STRONGEST SIGNAL FOR HEAVY RAINS  
OVER THE SOUTHEAST/SOUTHERN APPALACHIANS/EASTERN GULF COAST.  
THERE IS A THREAT OF MULTI-INCH RAINFALL TOTALS IN THE SOUTHEAST  
NEXT WEEK AS THE BLOCKING RIDGING CHANNELS SURGES OF MOISTURE AND  
LIFT ALONG THE SAME AXIS.  
 
THE ENSEMBLE SITUATIONAL AWARENESS TABLE HIGHLIGHTED THIS AREA  
WITH "MAX" VALUES PER THE GEFS QPF RELATIVE TO THE REFORECAST  
DATABASE, SIGNALING THE RARITY OF THE GEFS ENSEMBLES TO BE THIS  
WET THIS FAR OUT THIS TIME OF YEAR (JAN/FEB/MAR). COLDER AIR  
SETTLED IN PLACE ON THE NORTHERN PERIPHERY OF THESE LOW PRESSURE  
SYSTEMS OFFERS THREATS OF SNOW/ICE FOR THE GREAT LAKES, PORTIONS  
OF THE OHIO VALLEY, NORTHERN APPALACHIANS, AND NEW YORK/NEW  
ENGLAND.  
 
AS THE MAIN UPPER TROUGH AXIS MOVES INLAND, SNOWS WILL FOCUS  
ACROSS THE SOUTHWEST/SOUTHERN ROCKIES TERRAIN. HEAVY SNOWS ARE  
POSSIBLE IN THE RANGES OF AZ, INCLUDING THE MOGOLLON RIM.  
RAIN/MOUNTAIN SNOWS MAY RETURN TO THE PACIFIC NORTHWEST BY MIDWEEK  
AS A MORE SIGNIFICANT SHORTWAVE APPROACHES AND DIVES SOUTH ALONG  
THE COAST INTO THE WINTRY GREAT BASIN THEN ROCKIES/N-CENTRAL U.S.  
 
WELL-BELOW AVERAGE TEMPERATURES WILL PERSIST ACROSS MUCH OF THE  
WESTERN/CENTRAL U.S. DURING THE NEXT WEEK AS THE UPPER TROUGH AXIS  
MOVES INLAND. TEMPERATURES AS COLD AS 15 TO 25 DEG F BELOW AVERAGE  
WILL INITIALLY BE CONCENTRATED ACROSS THE NORTHERN/CENTRAL HIGH  
PLAINS SUN, IN THE SOUTHWEST TO CENTRAL PLAINS MON, SOUTHWEST TUE  
AND WED. OTHERWISE THE WESTERN US TEMPERATURES TO THE PLAINS  
STATES REMAIN BELOW NORMAL. RECORD COLD MAXIMUM TEMPERATURE ARE  
QUITE POSSIBLE OVER PORTIONS OF THE SOUTHWEST/SOUTHERN CALIFORNIA  
THROUGH THE PERIOD. FARTHER EAST NEAR THE UPPER RIDGE, RECORD HIGH  
TEMPERATURES WILL BE POSSIBLE ALONG THE GULF COAST INTO FLORIDA.  
 
PETERSEN/SCHICHTEL  
 
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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