761  
FXUS02 KWBC 022116  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION...CORRECTION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
415 PM EST SAT MAR 02 2019  
 
CORRECTION DUE TO TYPOS IN THE SECOND SECTION  
 
VALID 12Z TUE MAR 05 2019 - 12Z SAT MAR 09 2019  
   
..OVERVIEW
 
 
THE FLOW ACROSS THE CONUS WILL BEGIN THE MEDIUM RANGE IN A RATHER  
AMPLIFIED SETUP, AND THEN GRADUALLY TREND MORE ZONAL AND  
PROGRESSIVE BY THE MID TO LATTER PORTION OF THE FORECAST PERIOD.  
SHORTWAVE ENERGY EJECTING FROM A MEAN UPPER TROUGH OFF THE WEST  
COAST WILL CROSS THE COUNTRY EVERY COUPLE DAYS. MEANWHILE, A BROAD  
UPPER TROUGH INITIALLY IN PLACE ACROSS THE GREAT LAKES/NORTHEAST  
SHOULD GRADUALLY LIFT OUT BY THE MIDDLE TO END OF THE NEXT WORK  
WEEK.  
 
   
..MODEL GUIDANCE EVALUATION AND PREFERENCES
 
 
MODELS/ENSEMBLES CONTINUE TO SHOW GOOD CLUSTERING WITH RESPECT TO  
AN ENERGETIC UPPER SHORTWAVE AND LOW PRESSURE SYSTEM APPROACHING  
THE WEST COAST TUE NIGHT-WED, SUCH THAT A MULTI-MODEL CONSENSUS  
FORECAST WAS PREFERRED. AS THIS FEATURE MOVES INTO THE CENTRAL  
ROCKIES BY THU, THE SAME MODEL DIFFERENCES AS YESTERDAY CONTINUE  
TO PLAGUE THIS FEATURE. THE GFS CONTINUES TO KEEP A MORE AMPLIFIED  
SHORTWAVE ACROSS THE ROCKIES AND INTO THE CENTRAL U.S., WHILE THE  
CONSENSUS OF OTHER GUIDANCE CONTINUES TO WEAKEN THE WAVE AS IT  
ENCOUNTERS BROAD WEAKLY ANTICYCLONIC UPPER FLOW. THE DIFFERENCES  
INCREASE FURTHER BY THU NIGHT-FRI WITH THE GFS SPINNING UP A DEEP  
CYCLONE ACROSS THE CENTRAL PLAINS/MIDWEST, WHILE THE CONSENSUS OF  
OTHER GUIDANCE KEEP A WEAKER AND MORE SUPPRESSED SURFACE LOW  
ACROSS THE SOUTHERN PLAINS. ENSEMBLE MEANS CONTINUE TO PROVIDE  
LITTLE IN THE WAY OF SUPPORT FOR THE GFS SOLUTION AND IT WAS THUS  
REJECTED STARTING THU NIGHT-FRI. FLOW IN THE NORTHEAST PACIFIC  
BECOMES A BIT MORE CHAOTIC BY LATE IN THE FORECAST PERIOD, WITH  
THE ECMWF/CMC SHOWING SOME DEGREE OF SHORTWAVE ENERGY UNDERCUTTING  
THE NORTH PACIFIC/GULF OF ALASKA RIDGE, AND THE GFS KEEPING A  
STRONGER RIDGE INTACT. THERE IS SOME CONSENSUS, HOWEVER, THAT AN  
ADDITIONAL SHORTWAVE SHOULD MOVE INTO THE WESTERN U.S. ON FRI AND  
THEN REACH THE CENTRAL ROCKIES BY SAT. THE ECMWF AND CMC SOLUTIONS  
SHOWED THE BEST AGREEMENT WITH THE ENSEMBLE CONSENSUS ON THIS  
FEATURE.  
 
GIVEN THESE CONSIDERATIONS, THE FORECAST WAS INITIALLY BASED ON A  
MULTI-MODEL DETERMINISTIC BLEND (00Z ECMWF/UKMET/CMC AND 06Z GFS)  
DURING DAYS 3-5 (TUE-THU). FOR DAYS 6-7 (FRI-SAT), THE FORECAST  
WAS SHIFTED TO HEAVIER ENSEMBLE MEAN (ECENS AND NAEFS) WEIGHTING,  
WITH SOME CONTINUED EMPHASIS ON THE 00Z ECMWF/CMC SOLUTIONS AS  
WELL.  
 
   
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
 
 
COLD TEMPERATURES WILL CONTINUE TO MAKE HEADLINES AT THE BEGINNING  
OF THIS FORECAST PERIOD, WITH A STRONG ARCTIC SURFACE HIGH IN  
PLACE ACROSS THE CENTRAL/EASTERN U.S. HIGH TEMPERATURES ON TUESDAY  
OF 20 TO 35 DEGREES BELOW AVERAGE ARE EXPECTED ACROSS MUCH OF THE  
PLAINS EASTWARD ACROSS THE MIDWEST AND OHIO VALLEY. THIS EQUATES  
TO WIDESPREAD SUBZERO AND SINGLE DIGIT LOW TEMPERATURES, AND HIGHS  
ONLY IN THE TEENS AND LOW 20S FOR MANY OF THOSE AREAS.  
TEMPERATURES WILL ONLY SLOWLY MODERATE THROUGH MIDWEEK WITH  
TEMPERATURES 15 TO 30 DEGREES BELOW NORMAL ALSO EXTENDING EASTWARD  
TOWARDS THE MID-ATLANTIC AND NORTHEAST. THE MAGNITUDE AND COVERAGE  
OF THE COLD TEMPERATURES WILL ABATE SOME BY THE END OF THE WEEK,  
BUT BELOW NORMAL TEMPERATURES WILL CONTINUE FOR MANY AREAS THROUGH  
THE END OF NEXT WEEK.  
 
HEAVY RAIN AND MOUNTAIN SNOW ARE EXPECTED TO MAKE A RETURN TO THE  
WESTERN U.S. BY TUESDAY NIGHT AS AN ATMOSPHERIC RIVER EVENT  
ACCOMPANIES A STRONG PACIFIC LOW HEADED TOWARDS CALIFORNIA. HEAVY  
RAINFALL ACROSS THE LOWER ELEVATIONS OF CALIFORNIA MAY LEAD TO  
SOME FLOODING PROBLEMS, AND HEAVY SNOW IN THE SIERRA NEVADA WILL  
ADD TO THE ALREADY EXTENSIVE SNOW PACK. SIGNIFICANT SNOW IS  
FORECAST FOR THE CENTRAL AND NORTHERN ROCKIES BY WEDNESDAY AND  
THURSDAY AS THE MOISTURE PLUME SPREADS INLAND, ALBEIT NOT TO THE  
SAME DEGREE AS CALIFORNIA. RAIN IS EXPECTED TO BECOME BECOME  
WIDESPREAD FROM PORTIONS OF THE LOWER/MID-MISSISSIPPI VALLEY TO  
THE TENNESSEE VALLEY BY FRI INTO SAT AS A WARM FRONT SETS UP AHEAD  
OF A DEVELOPING CENTRAL U.S. LOW PRESSURE SYSTEM.  
 
RYAN/HAMRICK  
 
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  
 
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  
 

 
 
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