805  
FXUS02 KWBC 211532  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1032 AM EST THU FEB 21 2019  
 
VALID 12Z SUN FEB 24 2019 - 12Z THU FEB 28 2019  
 
...MAJOR UPPER MIDWEST/GREAT LAKES/INTERIOR NEW ENGLAND WINTER  
STORM SUNDAY/MONDAY...  
 
...PATTERN OVERVIEW.  
 
THE REX BLOCK PATTERN ACROSS THE CENTRAL/NORTH PACIFIC EXTENDING  
FROM NEAR HAWAII TO ALASKA WILL PERSIST OR EVEN STRENGTHEN DURING  
THE MEDIUM RANGE. THE STRONGEST POSITIVE HEIGHT ANOMALY CENTER  
WILL SHIFT NORTHWARD INTO THE ARCTIC BY THE EARLY TO MIDDLE  
PORTION OF NEXT WEEK. TELECONNECTIONS RELATIVE TO THIS SHIFT IN  
THE ANOMALY SUPPORT AN EASTWARD SHIFT OF THE MEAN TROUGH ACROSS  
THE CONUS/CANADA, FROM A POSITION WHICH AS BEEN ACROSS THE WESTERN  
U.S. TO A MEAN POSITION FROM HUDSON BAY TO THE UPPER MIDWEST BY  
THE MIDDLE OF NEXT WEEK. A SHIFT TO A MORE ZONAL FLOW REGIME  
ACROSS THE CONUS SOUTHERN TIER WILL ALSO BE A CONSEQUENCE OF THIS  
MODULATION ACROSS THE PACIFIC, AS SHORTWAVE ENERGY TAKE A MORE  
NORTHERN TRACK AND REINFORCES THE MEAN TROUGH/UPPER LOW.  
 
   
..GUIDANCE/PREDICTABILITY ASSESSMENT AND PREFERENCES
 
 
GUIDANCE WAS QUITE WELL CLUSTERED EARLY IN THE MEDIUM RANGE AT THE  
MID AND LARGER SCALES, AND A BLEND OF THE LATEST ECMWF/GFS/UKMET  
OFFERED A REASONABLE STARTING POINT FOR THE FORECAST DURING DAYS  
3-4 (SUN-MON). ONE ISSUE THAT EMERGES BY MON-TUE IS EXACTLY WHAT  
HAPPENS AS SHORTWAVE ENERGY INITIALLY ACROSS THE PACIFIC NORTHWEST  
SHEARS APART, WITH SOLUTIONS DIFFERING ON JUST HOW MUCH ENERGY  
MOVES EAST ACROSS THE CONUS AND CANADA VERSUS WESTWARD INTO THE  
PACIFIC UNDERNEATH THE RIDGE. AT THIS TIME, CONFIDENCE IS LOW IN  
THIS ASPECT OF THE FORECAST, AND THE OUTCOME DOES HAVE DOWNSTREAM  
IMPLICATIONS SUCH AS THE AMPLITUDE OF EASTERN U.S. TROUGHING BY  
NEXT TUE-WED. DESPITE THESE DISAGREEMENTS, MODEL/ENSEMBLE  
SOLUTIONS DO ALL SHOW A CONSISTENT PICTURE AT THE LARGER SCALES  
EVEN THROUGH DAY 7 AS ENERGY CONSOLIDATES INTO AN UPPER NEAR/SOUTH  
OF HUDSON BAY, WITH SHORTWAVES TRAVERSING THE SOUTHERN PERIPHERY  
THROUGH BROAD CYCLONIC FLOW FROM THE MIDWEST TO THE NORTHEAST.  
GIVEN THE INCREASED UNCERTAINTY AT MID/SMALL SCALES, WEIGHTING OF  
ECENS/GEFS ENSEMBLE MEANS WAS GRADUALLY INCREASED DURING DAYS 5-7  
(TUE-THU).  
 
   
..WEATHER HIGHLIGHTS/HAZARDS
 
 
A THREAT FOR SIGNIFICANT SNOWS/SOME ICING EXISTS AROUND A DEEP  
SURFACE LOW. THE RAPIDLY DEEPENING SYSTEM (CENTRAL PRESSURE FALL  
OF ABOUT 20MB/24 HRS BETWEEN SAT AND SUN MORNING) LIFTS INTO THE  
GREAT LAKES AND THEN EXITS OUT THE ST. LAWRENCE VALLEY SUNDAY INTO  
MONDAY. THIS SYSTEM HAS THE POTENTIAL TO DEEPEN INTO THE UPPER  
970S MB WHICH MAY BE CLOSE TO MONTHLY RECORD LOW PRESSURE VALUES  
FOR PORTIONS OF LOWER MICHIGAN SUNDAY. EXPECT STRONG/GUSTY WINDS  
AND POTENTIAL BLIZZARD CONDITIONS OVER THE UPPER MIDWEST/GREAT  
LAKES AND INTO CANADA SUNDAY-MONDAY. MILD AIR WILL SURGE NORTHWARD  
EAST OF A TRAILING COLD FRONT WITH A BRIEF SPIKE IN TEMPS TO THE  
60/70S AS FAR NORTH AS THE MID-ATLANTIC. FARTHER SOUTH, A  
PROLONGED HEAVY RAIN PATTERN WILL FINALLY END WITH COLD FRONTAL  
PASSAGE, WITH LEAD RECORD WARM TEMPS POSSIBLE OVER FLORIDA.  
 
A LONG-STANDING AND WINTRY MEAN UPPER TROUGH OVER THE WEST  
DEAMPLIFIES NEXT WEEK, BUT WILL STILL BE REINFORCED OVER THE  
NORTHWEST INTO SUN-MON AS ENERGY UNDERCUTS AND DIGS TO THE LEE OF  
A BLOCKING ALASKA-CENTERED CLOSING UPPER HIGH. THIS WILL BRING  
UNSETTLED WEATHER ACROSS THE NORTHWEST/NORTHERN CA AND THE  
NORTH-CENTRAL INTERMOUNTAIN WEST/ROCKIES. THE BEST CHANCE FOR  
HEAVY SNOW WILL BE FROM THE CASCADES TO ESPECIALLY NORTHERN CA  
WITH EMERGENCE OF UNCERTAIN PACIFIC FLOW UNDERCUTTING THE NORTHERN  
STREAM.  
 
FLATTER FLOW DOWNSTREAM OVER CENTRAL AND EASTERN U.S. NEXT WEEK  
REDUCES POTENTIAL FOR BIG STORMS, BUT A SERIES OF SMALLER/LESS  
PREDICTABLE SYSTEMS WILL PROGRESS OVER THE REGION. THIS WILL STILL  
FAVOR COLD AIR SURGES/ANOMALOUSLY COLD TEMPS THROUGH THE N-CENTRAL  
U.S. AND SNOW SWATHS OVER THE NORTHERN TIER STATES. RAINFALL ALSO  
REDEVELOPS ACROSS THE GULF COAST/FL WITH THE FRONTS, BUT GUIDANCE  
HAS BACKED OFF WITH AMOUNTS.  
 
RYAN/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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