312  
FXUS10 KWNH 221650  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1149 AM EST MON JAN 22 2018  
 
VALID JAN 22/1200 UTC THRU JAN 26/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z INITIAL MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST  
CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..DEEP LAYER CYCLONE OVER THE MIDWEST REGION TODAY
 
   
..SURFACE LOW CROSSING THE GREAT LAKES REGION THROUGH TUESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND THROUGH 6Z WEDNESDAY, THEN  
ECMWF/GFS COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS ARE OVERALL IN VERY GOOD AGREEMENT WITH THE DETAILS OF  
THE DEEP CLOSED LOW AND ITS ACCOMPANYING SURFACE LOW OVER THE  
UPPER MIDWEST AND THE GREAT LAKES REGION THROUGH 6Z WEDNESDAY.  
THERE IS A GOOD SIGNAL IN THE PMSL GUIDANCE THAT A TRIPLE POINT  
LOW COULD FORM ONCE THE STORM SYSTEM APPROACHES NEW ENGLAND  
TUESDAY NIGHT. BY 12Z WEDNESDAY, THE CMC APPEARS TO BE SLIGHTLY  
SLOWER IN LIFTING OUT THE UPPER TROUGH OVER NEW ENGLAND AND MORE  
PRONOUNCED WITH THE SURFACE COLD FRONT AS IT EXITS THE EAST COAST.  
THE NAM IS INDICATING A DUAL 700MB LOW STRUCTURE OVER SOUTHERN  
QUEBEC AT 12Z WEDNESDAY THAT THE OTHER GUIDANCE IS NOT ON BOARD  
WITH AT THE PRESENT TIME.  
 
...SHORTWAVE ENERGY DIGGING ACROSS THE NORTHERN PLAINS BY  
TUESDAY...   
..EASTERN U.S UPPER LEVEL TROUGH BY WEDNESDAY NIGHT
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND THROUGH 12Z WEDNESDAY, THEN  
NON-UKMET CONSENSUS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
A NORTHERN STREAM UPPER LEVEL TROUGH INITIALLY OVER ALBERTA TODAY  
IS FORECAST TO DIG TOWARDS THE SOUTHEAST THROUGH THE MIDDLE OF THE  
WEEK ACROSS THE NORTHERN PLAINS AND MIDWEST STATES, IN RESPONSE TO  
THE UPSTREAM RIDGING OVER THE INTERMOUNTAIN WEST. THE MODELS ARE  
IN GOOD AGREEMENT WITH THEIR MASS FIELD TIMING AND DEPTH THROUGH  
ABOUT 12Z WEDNESDAY. THEREAFTER, THE UKMET BECOMES LESS AMPLIFIED  
THAN THE MODEL CONSENSUS AND IS SLIGHTLY SLOWER. THE GFS IS NOW  
CLOSER TO THE MODEL CONSENSUS AND NOT AS PROGRESSIVE AS EARLIER  
MODEL RUNS.  
 
   
..SHORTWAVE IMPACTING THE PACIFIC NORTHWEST ON TUESDAY
 
   
..ATTENDANT SURFACE LOW LIFTING UP OFFSHORE BRITISH COLUMBIA
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS SHOW A SHORTWAVE ARRIVING ACROSS WESTERN WASHINGTON AND  
OREGON ON TUESDAY WITH THE SYSTEM THEN WEAKENING AS IT ENCOUNTERS  
A DEVELOPING RIDGE OVER THE GREAT BASIN AND CANADIAN ROCKIES. THIS  
WILL DRIVE A FOCUS OF STRONGER SOUTH/SOUTHWEST FLOW UP ALONG THE  
COASTAL RANGES OUT AHEAD OF A STRONG AREA OF LOW PRESSURE THAT  
LIFTS UP OFFSHORE BRITISH COLUMBIA. THE MODELS ARE IN GOOD  
AGREEMENT WITH THIS SYSTEM AS IT ARRIVES AND SO A GENERAL MODEL  
BLEND WILL BE PREFERRED.  
 
...DEEP UPPER TROUGH AND SURFACE LOW OFFSHORE THE WEST COAST BY  
WEDNESDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS ALLOW A LOW PRESSURE GYRE TO DEVELOP OFFSHORE THE  
BRITISH COLUMBIA AND PACIFIC NORTHWEST COAST FOR THE MIDDLE OF THE  
WEEK WITH STRONG SOUTHWEST ONSHORE FLOW SETTING UP ACROSS THE  
PACIFIC NORTHWEST. THIS WOULD BE SOUTH OF AN APPROACHING SURFACE  
LOW WHICH WILL BE NEAR VANCOUVER ISLAND BY THURSDAY MORNING.  
ALTHOUGH THERE IS GOOD OVERALL SYNOPTIC SCALE AGREEMENT, THERE ARE  
SOME DETAIL DIFFERENCES WITH THE STRENGTH AND POSITION OF THE  
UPPER LOW. THE GFS KEEPS THE LOW MORE TO THE NORTHWEST, WHEREAS  
THE ECMWF IS FARTHER SOUTH. BY THE END OF THE FORECAST PERIOD,  
THE GFS PIVOTS THE SURFACE LOW SOUTH OF THE MODEL CONSENSUS.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
HAMRICK  
 

 
 
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