856  
FXUS10 KWNH 221850  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
150 PM 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 FINAL 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 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. THE CMC HAS TRENDED CLOSER TO THE MODEL CONSENSUS  
REGARDING THE SPEED OF THE TROUGH AXIS, AND CAN BE CONSIDERED PART  
OF THE BLEND. 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, BUT IS OTHERWISE IN VERY  
GOOD AGREEMENT MASS FIELD WISE.  
 
...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  
GFS/ECMWF COMPROMISE  
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 AND ROCKY  
MOUNTAINS. THE MODELS ARE IN GOOD AGREEMENT WITH THEIR MASS FIELD  
TIMING AND DEPTH THROUGH ABOUT 12Z WEDNESDAY. THEREAFTER, THE  
UKMET AND CMC BECOME LESS AMPLIFIED THAN THE MODEL CONSENSUS AND  
THE CMC IS SLIGHTLY FASTER. 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 ENHANCE 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  
 
A LARGE LOW PRESSURE GYRE IS FORECAST TO DEVELOP ABOUT 500 MILES  
WEST OF 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 SMALLER DETAIL DIFFERENCES WITH THE  
STRENGTH AND POSITION OF SHORTWAVE ENERGY ROTATING AROUND IT .  
THE GFS INITIALLY 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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