682  
FXUS02 KWBC 121600  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1100 AM EST FRI JAN 12 2018  
 
VALID 12Z MON JAN 15 2018 - 12Z FRI JAN 19 2018  
   
..OVERVIEW
 
 
IT REMAINS THE CASE THAT THE MEDIUM RANGE PERIOD BEGINS ALOFT WITH  
A WESTERN RIDGE AND A LARGE CENTRAL AND EASTERN U.S. TROUGH THAT  
WILL GENERALLY TRANSLATE EASTWARD OVER THE COURSE OF NEXT WEEK AS  
A LARGE SCALE TROUGH BECOMES ESTABLISHED OVER THE WEST COAST. THE  
RIDGE SHOULD GENERALLY BECOME LESS AMPLIFIED ONCE IT REACHES THE  
CENTRAL U.S. WITH A COUPLE OF SHORT WAVE IMPULSES EMBEDDED WITHIN  
IT. THE PREDOMINANT SYSTEMS THAT MERIT ATTENTION WILL BE A STRONG  
CLIPPER SYSTEM THAT WILL CROSS THE GREAT LAKES/NERN U.S....AN  
ARCTIC INTRUSION ACROSS THE NORTH-CENTRAL U.S...AND HEAVY NWRN  
US/NRN CA PRECIPITATION WITH THE DELIVERY OF SEVERAL STORMS.  
 
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
MODELS AND ENSEMBLES ARE WELL CLUSTERED AND UNCERTAINTY IS BELOW  
AVERAGE INTO TUESDAY ACROSS MUCH OF THE NATION. A BLEND OF THE 00  
UTC GFS/ECMWF AND THEIR ENSEMBLES SEEM TO REPRESENT WELL MOST  
FEATURES. FORECAST CLUSTERING AND PREDICTABILITY WANES SOME IN THE  
WED-NEXT FRI TIMEFRAME JUST A SEVERAL POTENTIAL STORMS EFFECT THE  
NWRN US AND WELL DOWNSTREAM FROM THE GREAT LAKES TO JUST OFFSHORE  
THE MID-ATLANTIC AND NEW ENGLAND. A BLEND OF 00 UTC GEFS/ECMWF  
ENSEMBLE MEANS SEEM TO BEST RESPRESENT THE MORE PREDICTABLE  
WEATHER FEATURES IN THIS TIME FRAME INCLUDING AN INCREASING THREAT  
FOR ACTIVE STORMY WEATHER ON BOTH COASTS...BUT ALSO INCLUDED MINOR  
WEIGHTING TO THE MORE VARIED 00 UTC GFS/ECMWF TO ADD A BIT MORE  
DETAIL.  
 
OVERALL...THERE REMAINS A STRONG SIGNAL FOR THE UPCOMING  
STORMY/WET PATTERN TO EFFECT THE NWRN US/NRN CA WITH DEEP STORM  
TRACKS LEADING TO A SIGNIFICANT WIND/SEA/PCPN THREAT. THERE IS  
ALSO A GOOD SIGNAL FOR ONE OR MORE COASTAL LOWS TO PRIMARILY  
EFFECT THE NERN US...BUT UNCERTAINTY REMAINS WITH THE PROXIMITY OF  
THE COASTAL TRACK AND INLAND EXTENT OF HEAVY WRAPBACK SNOWS AS  
ENERGY ROTATES THROUGH THE AMPLIFIED SUPPORTING MID-UPPER LEVEL  
MEAN TROUGH POSIITON.  
 
   
..WEATHER/THREATS HIGHLIGHTS
 
 
A WELL DEVELOPED CLIPPER SYSTEM IS FORECAST TO DELIVER ANOTHER  
ROUND OF SNOWFALL TO THE GREAT LAKES...FOLLOWED BY A FRESH SURGE  
OF ARCTIC AIR BEHIND THE TRAILING COLD FRONT. FRIGID CONDITIONS  
ARE EXPECTED FROM ERN MT TO THE UPPER MIDWEST INTO TUESDAY WITH  
SOME HIGHS FAILING TO REACH ZERO. OVERNIGHT LOWS COULD REACH THE  
MINUS 20S ACROSS PARTS OF ND/MN AND VICINITY...WITH SOME MINUS 30S  
POSSIBLE. THESE FRIGID TEMPS WOULD BE 20-30 DEGREES BELOW NORMAL.  
IT WILL ALSO BECOME QUITE COLD WELL SOUTHWARD THROUGH THE REST OF  
THE CENTRAL AND ERN US DURING THE PERIOD GIVEN THE MAGNITUDE OF  
THE SURFACE HIGH THAT FOLLOWS BEHIND THE CLIPPER SYSTEM. SOME  
RECORD LOW TEMPERATURES WILL BE POSSIBLE WHERE RADIATIONAL COOLING  
IS MAXIMIZED.  
 
ABOVE AVERAGE TEMPERATURES ARE EXPECTED NEXT WEEK FOR THE SWRN  
U.S. AND EXTENDING INTO THE GREAT BASIN. PRECIPITATION INCREASES  
AGAIN OVER THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA MONDAY  
WITH MULTIPLE ROUNDS OF UNSETTLED CONDITIONS FOR THE COAST THROUGH  
FRIDAY. THERE SHOULD MORE OF AN INTERLUDE BETWEEN THE FIRST AND  
SECOND SYSTEMS FURTHER INLAND. THE SYSTEM TOWARDS THE END OF THE  
WEEK ADVECTS MORE MOISTURE INTO THE REGION WITH SOME LOCATIONS  
POSSIBLY RECEIVING SEVERAL INCHES OF RAIN AND OVER A FOOT OF  
MOUNTAIN SNOW.  
 
SCHICHTEL  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page