490  
FXUS02 KWBC 111608  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1107 AM EST THU JAN 11 2018  
 
VALID 12Z SUN JAN 14 2018 - 12Z THU JAN 18 2018  
   
..STORMS TO THREATEN THE NWRN US AND NERN US NEXT WEEK
 
 
   
..OVERVIEW
 
 
A MORE BENIGN WEATHER PATTERN IS ON TAP SUN-MON OVER MOST OF THE  
LOWER 48 AS A CLIPPER SYSTEM DIVES THROUGH THE GREAT LAKES. THERE  
IS A THREAT TO SPIN UP A DEEPENED MID-ATLANTIC TO NEW ENGLAND  
COASTAL STORM BY TUE/WED WITH THIS AND/OR THE DIGGING OF UPSTREAM  
NRN STREAM SHORTWAVE ENERGY. THE WEST WILL BE BECOME MUCH MORE  
ACTIVE AS WELL AS THE UPPER RIDGE YIELDS COMPLETELY TO STRONG FLOW  
OUT OF THE NERN PACIFIC AND HEIGHT FALLS/FRONTS MOVE THROUGH  
WA/OR/NRN CA TUE-THU IN AN INCREASINGLY WET AND UNSETTLED PATTERN.  
 
   
..GUIDANCE ASSESSMENT/PREFERENCES
 
 
MODELS AND ENSEMBLES ARE WELL CLUSTERED AND UNCERTAINTY IS BELOW  
AVERAGE DAYS INTO MONDAY ACROSS MUCH OF THE NATION. A BLEND OF THE  
06 UTC GFS AND 00 UTC ECMWF SEEMS TO REPRESENT WELL. FORECAST  
CLUSTERING AND PREDICTABILITY WANES SOME IN THE TUE-THU TIMEFRAME  
JUST A SEVERAL POTENTIAL STORMS WORK TOWARD THE NWRN US AND WELL  
DOWNSTREAM FROM THE GREAT LAKES TO JUST OFFSHORE THE MID-ATLANTIC  
AND NEW ENGLAND. A BLEND OF THE 06 UTC GEFS AND 00 UTC ECMWF SEEMS  
TO BEST RESPRESENT THE MORE PREDICTABLE WEATHER FEATURES IN THIS  
TIME FRAME INCLUDING AN INCREASING THREAT FOR ACTIVE STORMY  
WEATHER ON BOTH COASTS. THERE IS A GOOD SIGNAL FOR ONE OR MORE  
SUCH COASTAL LOWS TO SIGNNIFICANTLY EFFECT THE NERN US AND  
POSSIBLY THE COASTAL MID-ATLANTIC IF A SOLUTION CLOSE TO THE  
OUTLIER ECMWF IS CLOSE TO CORRECT WITH THE EXTENT OF SUPPORTING  
MID-UPPER LEVEL TROUGH AMPLIFICATION. FOR NOW...WPC PROGS ONLY  
ADJUSTED THE OVERNIGHT LOW POSITION CONTINUITY SLIGHTLY SOUTHWARD  
OFF THE NORTHEAST MIDWEEK TO ACCOUNT FOR LATEST OVERALL GUIDANCE  
TRENDS/CLUSTERING. THE 06 UTC GFS AND 00 UTC ECMWF NOW DO OFFER A  
DEEPER TROUGH ALOFT...BUT MUCH UNCERTAINTY REMAINS AS MUCH OF  
ASSOCIATED ENERGY TO DIG INTO THIS FEATURE IS CURRENTLY WAY UP IN  
THE ARCTIC.  
 
   
..WEATHER HIGHLIGHTS
 
 
A WELL DEVELOPED CLIPPER SYSTEM WILL BRING LIGHT TO MODERATE SNOWS  
TO THE GREAT LAKES (WITH LOCAL ENHANCEMENT) AND ANOTHER PUSH OF  
COLDER AIR (SUB-ZERO HIGHS FOR MUCH OF THE DAKOTAS AND MINNESOTA  
ON MONDAY. TEMPERATURES 10-25 DEGREES BELOW AVERAGE WILL LINGER IN  
THE CENTRAL AND ERN US NEXT WEEK AS A SERIES OF COLD HIGH PRESSURE  
CELLS DIG FAR SOUTHWARD IN THE WAKE OF THE LOWS. UNCERTAINTY  
ABOUNDS WITH HOW THE CLIPPER SYSTEM TURN THE CORNER NEAR THE  
NORTHEAST AND THE EXTENT OF MIDWEEK ERN US MID-UPPER LEVEL TROUGH  
AMPLITUDE AND THREAT OF HEAVY SNOW WITH POTENTIAL MID-ATLANTIC/NEW  
ENGLAND COASTAL LOWS.  
 
ABOVE AVERAGE TEMPERATURES WILL RULE FOR NEXT WEEK IN THE WEST  
EVEN AFTER THE FIRST FRONT/HEIGHT FALLS WORKS THROUGH.  
PRECIPITATION RAMPS UP OVER THE PAC NW/NRN CA MONDAY AND CONTINUES  
WITH FEW BREAKS FOR THE COAST THROUGH THURSDAY. EAST OF THE  
CASCADES...THERE SHOULD BE AT LEAST SOME RESPITE BETWEEN THE FIRST  
AND SECOND SYSTEM. A SECOND DEEP SYSTEM APPROACH ALLOWS MORE  
MOISTURE TO FEED INTO THE REGION AND THIS IS REFLECTED IN THE  
HIGHER ENSEMBLE PROBABILITIES OF AT LEAST AN INCH OF QPF AND HIGH  
IVT RELATIVE TO CLIMATOLOGY.  
 
SCHICHTEL  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page