774  
FXUS02 KWBC 020700  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
159 AM EST SAT MAR 2 2019  
 
VALID 12Z TUE MAR 5 2019 - 12Z SAT MAR 9 2019  
 
WEATHER PATTERN OVERVIEW  
~~~~~~~~~~~~~~~~~~~~~~~~  
 
A RETURN TO A MORE AMPLIFIED UPPER LEVEL FLOW PATTERN IS EXPECTED  
ACROSS THE CONTINENTAL U.S. FOR THE EARLY TO MIDDLE PART OF NEXT  
WEEK. THE PASSAGE OF A STRONG COLD FRONT ACROSS THE EASTERN U.S.  
BY MONDAY WILL HERALD A MUCH COLDER AIRMASS ACROSS THE CENTRAL AND  
EASTERN U.S., ACCOMPANIED BY A PRONOUNCED UPPER LEVEL TROUGH AND  
SPRAWLING SURFACE HIGH FROM CANADA. THE PRESENCE OF THE EASTERN  
U.S./CANADA TROUGH SUPPORTS A BROAD UPPER RIDGE ACROSS THE ROCKIES  
AND HIGH PLAINS BY MIDWEEK, WHICH GRADUALLY FLATTENS OUT TOWARDS  
THE END OF THE FORECAST PERIOD AS THE FLOW RETURNS MORE  
QUASI-ZONAL WITH SOME SHORTWAVE PERTURBATIONS PASSING THROUGH. AN  
UNSETTLED WEATHER PATTERN IS EXPECTED TO RETURN ACROSS THE WEST  
COAST REGION AS MULTIPLE PACIFIC DISTURBANCES MOVE INLAND, WITH A  
LARGE SCALE TROUGH EXPECTED ACROSS THE INTERMOUNTAIN WEST BY THE  
END OF THE WEEK.  
 
MODEL GUIDANCE EVALUATION AND PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
THE DETERMINISTIC MODEL GUIDANCE IS IN ABOVE AVERAGE AGREEMENT FOR  
THE TUESDAY AND EARLY WEDNESDAY TIME PERIOD OWING LARGELY TO THE  
AMPLIFIED FLOW. THIS ESPECIALLY HOLDS TRUE FOR THE LARGE SCALE  
UPPER LEVEL TROUGH ANCHORED OVER THE EASTERN HALF OF THE NATION  
THROUGH MIDWEEK. THE MAIN FORECAST CHALLENGE, SIMILAR TO  
YESTERDAY, RESIDES OVER THE WEST COAST REGION BEGINNING ON  
WEDNESDAY WITH THE DEVELOPMENT OF A REX BLOCK OVER THE NORTHEAST  
PACIFIC. THE UKMET IS INDICATING A TRACK NORTH OF THE MODEL  
CONSENSUS WITH THE NEXT STORM TO AFFECT CALIFORNIA, AND REASONABLY  
GOOD AGREEMENT AMONG THE OTHER GUIDANCE. MORE NOTICEABLE  
DIFFERENCES ARE EVIDENT AS THIS FEATURE CROSSES THE ROCKIES AND  
EMERGES OVER THE HIGH PLAINS ON FRIDAY, WITH THE OPERATIONAL GFS  
WELL TO THE NORTH OF THE MODEL CONSENSUS, SO MORE OF THE FV3 MODEL  
WAS INCORPORATED IN PLACE OF THE GFS.  
 
THE FORECAST WAS PRIMARILY DERIVED WITH A BLEND OF THE LATEST  
DETERMINISTIC SOLUTIONS (ECMWF/GFS/FV3/CMC) AS A STARTING POINT  
FOR THE TUESDAY THROUGH THURSDAY TIME PERIOD. FOR FRIDAY AND  
SATURDAY, THE GEFS AND EC MEANS ALONG WITH SMALLER PERCENTAGES OF  
THE FV3 AND ECMWF WERE INCORPORATED INTO THE FORECAST PROCESS. NO  
MAJOR CHANGES FROM PREVIOUS WPC CONTINUITY WERE WARRANTED.  
 
SENSIBLE WEATHER AND POTENTIAL HAZARDS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
MUCH COLDER WEATHER WILL BE MAKING HEADLINES AT THE BEGINNING OF  
THIS FORECAST PERIOD AFTER THE PASSAGE OF A STRONG COLD FRONT ON  
MONDAY. A MASSIVE ARCTIC SURFACE HIGH WILL ENCOMPASS ALL OF THE  
CENTRAL AND EASTERN U.S. THROUGH THE MIDDLE OF THE WEEK, AND  
REACHING WELL INTO EASTERN MEXICO. THE PROJECTED DEPARTURES FROM  
EARLY MARCH CLIMATOLOGY WILL BE IMPRESSIVE, WITH HIGH TEMPERATURES  
ON TUESDAY ON THE ORDER OF 20 TO 35 DEGREES BELOW NORMAL ACROSS  
MUCH OF THE PLAINS AND EXTENDING EASTWARD ACROSS THE MIDWEST AND  
OHIO VALLEY. THIS EQUATES TO WIDESPREAD SUBZERO AND SINGLE DIGIT  
LOW, AND HIGHS ONLY IN THE TEENS AND LOW 20S FOR MANY OF THOSE  
AREAS. THERE WILL LIKELY BE NUMEROUS DAILY RECORD LOWS TO BE  
ESTABLISHED WITH THIS ARCTIC AIRMASS, WITH THE GREATEST POTENTIAL  
FOR THIS ON TUESDAY MORNING. TEMPERATURES ONLY SLOWLY MODERATE  
THROUGH MIDWEEK WITH ANOMALIES OF 15 TO 30 DEGREES BELOW NORMAL,  
AND THIS WILL EXTEND EASTWARD TOWARDS THE MID-ATLANTIC AND  
NORTHEAST. ALTHOUGH THE MAGNITUDE OF THE COLD TEMPERATURES WILL  
ABATE SOME BY THE END OF THE WEEK, BELOW NORMAL TEMPERATURES WILL  
BE THE RULE FOR THE ENTIRE FORECAST PERIOD.  
 
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. THE  
SIERRA NEVADA WILL LIKELY GET HAMMERED BY VERY HEAVY SNOW, THUS  
ADDING TO ITS EXTENSIVE SNOW PACK. SIGNIFICANT SNOW IS FORECAST  
FOR THE CENTRAL AND NORTHERN ROCKIES BY WEDNESDAY AND THURSDAY AS  
THE MOISTURE PLUME ADVECTS INLAND, ALBEIT NOT TO THE SAME DEGREE  
AS CALIFORNIA. HEAVY RAINFALL ACROSS THE LOWER ELEVATIONS OF  
CALIFORNIA MAY LEAD TO SOME FLOODING PROBLEMS, AND FUTURE  
EXCESSIVE RAINFALL OUTLOOKS WILL HAVE ADDITIONAL INFORMATION AS  
THIS EVENT ENTERS THE SHORT RANGE FORECAST PERIOD.  
 
D. 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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