217  
FXUS02 KWBC 012019  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
318 PM EST FRI MAR 01 2019  
 
VALID 12Z MON MAR 04 2019 - 12Z FRI MAR 08 2019  
 
1500 UTC UPDATE...  
 
OVERALL MODEL/ENSEMBLE CONSENSUS REMAINS ABOVE AVERAGE THROUGH  
MUCH OF THE MEDIUM RANGE, WITH GENERAL AGREEMENT AT THE LARGE  
SCALE EVEN THROUGH DAY 7. CLUSTERING OF SOLUTIONS WAS SUFFICIENT  
BOTH WITH RESPECT TO THE LOW PRESSURE SYSTEM OFF NEW ENGLAND ON  
DAY 3 (MON) AND A LOW PRESSURE SYSTEM APPROACHING CALIFORNIA ON  
DAY 5 (WED) THAT A MULTI-MODEL DETERMINISTIC BLEND (INCLUDING THE  
ECMWF/UKMET/CMC/GFS/FV3) SERVED AS A GOOD FORECAST STARTING POINT.  
DIFFERENCES EMERGE AFTER DAY 5 WITH RESPECT TO HOW THIS WEST COAST  
SYSTEM EVOLVES AS IT MOVES INLAND, WITH THE GFS (AND CMC) KEEPING  
A MUCH MORE AMPLIFIED SHORTWAVE ACROSS THE ROCKIES AND CENTRAL  
U.S. DAYS 6-7 (THU-FRI) RELATIVE TO THE ECMWF/FV3 WHICH QUICKLY  
WEAKEN THE ENERGY AS IT MOVES INTO BROAD ANTICYCLONIC FLOW. AT  
THIS TIME ENSEMBLE MEANS ALL SUPPORT THE EXISTENCE OF THIS BROAD  
ANTICYCLONIC FLOW OVER THE ROCKIES BY THAT TIME, SO SUPPORT FOR  
THE GFS SOLUTIONS SEEMS LIMITED. THUS, CHOSE TO WITH A SOLUTION  
FOR DAYS 6-7 BASED ON A BLEND OF THE ECMWF AND MAJORITY ENSEMBLE  
MEANS (ECENS AND GEFS). FOR THE MOST PART, ADJUSTMENTS TO  
CONTINUITY WERE RELATIVELY SMALL. THE PREVIOUS DISCUSSION FROM  
OVERNIGHT FOLLOWS BELOW.  
 
RYAN  
 
PREVIOUS DISCUSSION (ISSUED AT 0643 UTC)...  
   
..OVERVIEW
 
 
A RETURN TO A MORE AMPLIFIED UPPER LEVEL FLOW PATTERN IS EXPECTED  
ACROSS THE CONTINENTAL U.S. FOR NEXT WEEK. THE PASSAGE OF A  
STRONG COLD FRONT ACROSS THE EASTERN U.S. BY MONDAY MORNING 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. AN UNSETTLED WEATHER PATTERN IS EXPECTED TO  
RETURN ACROSS THE WEST COAST REGION AS MULTIPLE PACIFIC  
DISTURBANCES MOVE INLAND.  
 
   
..MODEL GUIDANCE EVALUATION AND PREFERENCES
 
 
WITH THE TRANSITION TO A MORE AMPLIFIED PATTERN OVER THE  
CONTINENTAL U.S. COMPARED TO THE QUASI-ZONAL PATTERN IN THE SHORT  
RANGE PERIOD, THERE HAS BEEN AN IMPROVEMENT IN MODEL AGREEMENT  
OVER THE PAST FEW MODEL CYCLES REGARDING THE MEDIUM RANGE FORECAST  
PERIOD NEXT WEEK. THIS PARTICULARLY PERTAINS TO THE LARGE SCALE  
UPPER LEVEL TROUGH ANCHORED OVER THE EASTERN HALF OF THE NATION  
THROUGH THURSDAY, ALTHOUGH THE 12Z ECMWF INDICATES A FASTER  
SHORTWAVE PROGRESSION ACROSS THE EASTERN U.S. ON TUESDAY COMPARED  
TO THE OTHER GUIDANCE.  
 
THE MAIN FORECAST CHALLENGE RESIDES OVER THE WEST COAST REGION  
BEGINNING ON WEDNESDAY WITH THE APPROACH OF A STRONG PACIFIC STORM  
SYSTEM TOWARDS CALIFORNIA. THE 12Z ECMWF AND THE EC MEAN ARE  
SUGGESTING A MORE NORTHERN TRACK WITH THE SURFACE LOW, AND THE GFS  
AND CMC ARE INDICATING A SOUTHERLY TRACK, WITH THE GEFS MEAN CLOSE  
TO THE MODEL CONSENSUS. THERE ARE INDICATIONS IN THE  
DETERMINISTIC GUIDANCE AND MANY ENSEMBLE MEMBERS THAT A REX BLOCK  
MAY TRY TO DEVELOP OVER THE NORTHEAST PACIFIC AND WESTERN CANADA  
AS AN UPPER RIDGE TRIES TO BUILD NORTH OF THE WEST COAST UPPER  
TROUGH. THIS IS WHERE THE GREATEST MODEL DIFFERENCES CURRENTLY  
EXIST DURING THE SECOND HALF OF THE FORECAST PERIOD, AND THE  
ENSEMBLE MEANS PROVIDE A MORE REASONABLE IDEA ON PLACEMENT OF MAIN  
WEATHER FEATURES.  
 
THE FORECAST WAS PRIMARILY DERIVED WITH A BLEND OF THE LATEST  
DETERMINISTIC SOLUTIONS (ECMWF/GFS/CMC/UKMET) AS A STARTING POINT  
FOR THE MONDAY THROUGH WEDNESDAY TIME PERIOD. FOR THURSDAY AND  
FRIDAY, THE GEFS AND EC MEANS ALONG WITH SMALLER PERCENTAGES OF  
THE AFOREMENTIONED DETERMINISTIC MODEL WERE INCORPORATED INTO THE  
FORECAST PROCESS. NO MAJOR CHANGES FROM PREVIOUS WPC CONTINUITY  
WERE WARRANTED.  
 
   
..SENSIBLE WEATHER AND POTENTIAL HAZARDS
 
 
THE WINTER STORM ACROSS THE EAST COAST MONDAY MORNING WILL BE  
INTENSIFYING AS IT CONTINUES TRACKING TOWARDS THE NORTHEAST AND  
EXITING NEW ENGLAND LATER THAT DAY. HEAVY SNOW IS LIKELY TO BE  
ONGOING ACROSS INTERIOR PORTIONS OF NEW ENGLAND AND RAIN FOR  
COASTAL AREAS, WITH MOST OF THE PRECIPITATION ENDING PRIOR TO 12Z  
MONDAY. BEHIND THIS NOR'EASTER WILL BE A STRONG COLD FRONT THAT  
WILL USHER IN AN ANOMALOUSLY COLD AIR MASS BY EARLY MARCH  
STANDARDS. A HUGE ARCTIC SURFACE HIGH WILL ENCOMPASS ALL OF THE  
CENTRAL AND EASTERN U.S. THROUGH THE MIDDLE OF THE WEEK, AND  
REACHING WELL INTO MEXICO. THE PROJECTED DEPARTURES FROM EARLY  
MARCH CLIMATOLOGY ARE ASTOUNDING, WITH HIGH TEMPERATURES ON MONDAY  
ON THE ORDER OF 35 TO 40 DEGREES BELOW NORMAL ACROSS MUCH OF THE  
CENTRAL AND NORTHERN PLAINS, AND EXTENDING EASTWARD ACROSS THE  
UPPER MIDWEST! THIS EQUATES TO SUBZERO LOWS FROM MONTANA TO LAKE  
MICHIGAN, AND HIGHS IN THE SINGLE DIGITS AND LOW TEENS. THERE  
WILL BE A HIGH LIKELIHOOD FOR NUMEROUS DAILY RECORD LOWS TO BE  
ESTABLISHED WITH THIS ARCTIC AIRMASS. TEMPERATURES ONLY SLOWLY  
MODERATE THROUGH TUESDAY AND WEDNESDAY WITH ANOMALIES OF 20 TO 30  
DEGREES BELOW NORMAL, AND THIS WILL EXTEND EASTWARD TOWARDS THE  
APPALACHIANS. COLD WEATHER WILL CONTINUE THROUGH THE REMAINDER OF  
THE WEEK ACROSS THESE AREAS.  
 
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  
 
HAZARDS:  
- HEAVY RAIN ACROSS PORTIONS OF CALIFORNIA, TUE-WED, MAR 5-MAR 6.  
- HEAVY SNOW FOR THE SIERRA NEVADA, TUE-THU, MAR 5-MAR 7.  
- HEAVY SNOW ACROSS PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES,  
WED-THU, MAR 6-MAR 7.  
- HEAVY SNOW ACROSS PORTIONS OF THE CENTRAL AND SOUTHERN ROCKIES,  
WED-FRI, MAR 6-MAR 8.  
- HEAVY SNOW ACROSS PORTIONS OF NORTHERN NEW ENGLAND, MON, MAR 4.  
- FLOODING POSSIBLE ACROSS PORTIONS OF THE MID-ATLANTIC.  
- 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.  
- MUCH BELOW NORMAL TEMPERATURES FROM PORTIONS OF THE NORTHWEST TO  
THE GREAT LAKES AND THE NORTHEAST, MON-FRI, MAR 4-MAR 8.  
- MUCH BELOW NORMAL TEMPERATURES FROM THE CENTRAL AND SOUTHERN  
PLAINS TO THE OHIO VALLEY AND THE SOUTHEAST, MON-WED, MAR 4-MAR 6.  
- HIGH WINDS ACROSS PORTIONS OF WESTERN ALASKA AND THE ALASKAN  
PENINSULA, MON-WED, MAR 4-MAR 6.  
- HIGH WINDS ACROSS PORTIONS OF THE ALEUTIANS, WED-FRI, MAR 6-MAR  
8.  
- HIGH SIGNIFICANT WAVE HEIGHTS FOR COASTAL PORTIONS OF MAINLAND  
ALASKA, MON-TUE, MAR 4-MAR 5.  
- HIGH SIGNIFICANT WAVE HEIGHTS FOR COASTAL PORTIONS OF THE  
ALEUTIANS, WED-FRI, MAR 6-MAR 8.  
 
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  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page