309  
FXUS02 KWBC 161606  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1105 AM EST SAT FEB 16 2019  
 
VALID 12Z TUE FEB 19 2019 - 12Z SAT FEB 23 2019  
 
...MULTI-DAY THREAT OF HEAVY RAIN FOR THE TENNESSEE VALLEY TO  
SOUTHERN/CENTRAL APPALACHIANS, WITH WINTRY PRECIPITATION LIKELY ON  
THE NORTHERN EDGE IN THE MID-MISSISSIPPI/OHIO  
VALLEY/MID-ATLANTIC...  
 
...COLD WEATHER WILL PERSIST IN THE WESTERN TO CENTRAL U.S., WITH  
UNSETTLED WEATHER COMING INTO THE SOUTHWEST...  
 
   
..OVERVIEW
 
 
TROUGHING IN THE WESTERN U.S. WILL BE PERSISTENT DURING THE MEDIUM  
RANGE PERIOD, REINFORCED BY SHOTS OF RENEWED ENERGY. THIS FEATURE  
PLUS THE UNYIELDING UPPER HIGH IN THE WESTERN ATLANTIC WILL CREATE  
A FAVORABLE PATTERN FOR HEAVY PRECIPITATION IN THE SOUTHEASTERN  
U.S.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT AND PREFERENCES
 
 
MODEL GUIDANCE IS GENERALLY RATHER AGREEABLE IN THE LARGE SCALE  
PATTERN OF POTENT UPPER TROUGHS/HEIGHT FALLS PROGRESSING OVERTOP A  
NORTHEAST PACIFIC RIDGE THAT THEN DIG SHARPLY SOUTHWARD TO  
REINFORCE A WESTERN U.S. MEAN TROUGH. ANOTHER MID/UPPER-LEVEL  
TROUGH WILL EJECT FROM THE SOUTHWEST TO NORTHEAST TUE-THU, WHICH  
GUIDANCE ALSO SEEMS TO HANDLE WELL. THE MEDIUM RANGE SUITE WAS  
DERIVED FROM A MULTI-MODEL BLEND OF THE OPERATIONAL 00Z AND 06Z  
GFS, THE 00Z ECMWF, AND THE 00Z EC ENSEMBLE AND GEFS MEANS, WITH  
MORE OF A DETERMINISTIC COMPONENT THAN NORMAL BY DAY 6-7 DUE TO  
THE GOOD MODEL AGREEMENT AND TO MAINTAIN DETAILS OF STRENGTH. THE  
CMC WAS EXCLUDED FROM THE BLEND, HOWEVER, AS BY DAY 4-5 A TROUGH  
IN THE GULF OF ALASKA BECAME MORE PROGRESSIVE THAN OTHER MODELS,  
WHICH NEGATIVELY AFFECTED THE DOWNSTREAM FEATURES ACROSS THE  
CONUS.  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
HEAVY PRECIPITATION IN THE SOUTHEASTERN U.S. WILL BE THE MAIN  
STORY ACROSS THE CONUS NEXT WEEK. LEAD DEEP LAYERED AND  
ANOMALOUSLY MOIST SOUTHWEST FLOW CHANNELED FROM THE SOUTHERN  
PLAINS TO THE EAST WILL ACT TO SUSTAIN A SOUTHEAST RIDGE AND FUEL  
MULTI-DAY THREATS OF HEAVY RAIN/TRAINING FROM THE LOWER  
MISSISSIPPI/TENNESSEE VALLEYS TO THE SOUTHERN/CENTRAL  
APPALACHIANS. ON THE NORTHERN EDGE, A COLD SURFACE HIGH AND COLD  
AIR DAMMING IN THE MID-ATLANTIC REGION IS EXPECTED, LEADING TO  
FROZEN PRECIPITATION. POTENTIALLY HEAVY SNOW AND ICE IS A  
POSSIBILITY FROM THE MIDDLE MISSISSIPPI VALLEY TO OHIO VALLEY AND  
NORTHERN MID-ATLANTIC REGION.  
 
WITH ANOMALOUSLY LOW HEIGHTS IN THE WESTERN U.S., MUCH BELOW  
AVERAGE TEMPERATURES WILL PREVAIL FOR THE WESTERN AND CENTRAL U.S.  
A SURFACE LOW IS PROGGED TO MAKE ITS WAY INTO CALIFORNIA ON DAY 5  
(THU) AND MOVE THROUGHOUT THE SOUTHWEST THE NEXT COUPLE OF DAYS,  
WHICH WILL LEAD TO ENHANCED PRECIPITATION FOR THE SOUTHWEST,  
INCLUDING HIGHER ELEVATION SNOW.  
 
TATE/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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