793  
FXUS02 KWBC 011552  
PMDEPD  
 
EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1052 AM EST THU FEB 01 2018  
 
VALID 12Z SUN FEB 04 2018 - 12Z THU FEB 08 2018  
   
..PATTERN OVERVIEW
 
 
LITTLE CHANGE IN THE LONGWAVE PATTERN IS EXPECTED DURING THE  
PERIOD SPANNING FEBRUARY 4-8 AS DEEP CYCLONIC FLOW REMAINS  
ENTRENCHED ACROSS THE CENTRAL/EASTERN U.S. WHILE THE CORE OF LOWER  
HEIGHTS SHOULD REMAIN FIXED NORTH OF THE INTERNATIONAL BORDER...A  
SERIES OF EMBEDDED SHORTWAVES WILL BE FOCI FOR WAVES OF LOW  
PRESSURE WITH ASSOCIATED PRECIPITATION THREATS. MORE  
SPECIFICALLY...AN EXPECTED DUAL LOW STRUCTURE SHOULD BE EXITING  
OFFSHORE OF NEW ENGLAND ON 05/1200Z WHILE AN ADDITIONAL SYSTEM IS  
FORECAST TO CROSS THE CENTRAL APPALACHIANS BY THE MIDDLE OF NEXT  
WEEK. ACROSS THE EASTERN PACIFIC AND INTO THE WESTERN U.S...AN  
EXPANSIVE UPPER RIDGE SHOULD DRIFT EASTWARD IN TIME WITH A MEAN  
POSITION JUST EAST OF 130W BY 08/1200Z. WHILE A POSITIVE HEIGHT  
ANOMALY APPEARS TO BE A MAINSTAY FEATURE OF INTEREST...A PAIR OF  
MODEST SHORTWAVES SHOULD PUSH THROUGH THE PACIFIC NORTHWEST/UPPER  
INTERMOUNTAIN ON FEBRUARY 5 AND 8...RESPECTIVELY.  
 
   
..MODEL GUIDANCE/UNCERTAINTY ASSESSMENT/PREFERENCES
 
 
OVERALL...THERE IS REMARKABLE MODEL AGREEMENT THROUGHOUT THE  
PERIOD ALTHOUGH SOME MOVEMENT IN THE SOLUTIONS IS LIKELY TO COME  
IN THE DAYS AHEAD. REGARDING THE SHARPENING SHORTWAVE BECOMING  
NEGATIVELY TILTED OVER THE NORTHEASTERN U.S...A PAIR OF SURFACE  
CYCLONES ARE LIKELY TO EVOLVE OVER INTERIOR NEW ENGLAND AND THE  
COASTAL MID-ATLANTIC. EXCEPT FOR THE 06Z/00Z GFS SOLUTIONS...TWO  
WAVES SHOULD DEVELOP WITH THE NORTHERN STREAM ONE BECOMING MORE  
DOMINANT. ENSEMBLE LOW PLOTS STILL DEPICT QUITE A BIT OF  
NORTH/SOUTH SPREAD OVER THE WESTERN ATLANTIC AND INTO NEW  
BRUNSWICK. WHILE THIS SYSTEM STRENGTHENS CONSIDERABLY OVER THE  
HIGHER LATITUDES...THE FOCUS SHIFTS TOWARD PROGRESSIVE HEIGHT  
FALLS SWINGING THROUGH THE UPPER INTERMOUNTAIN WEST/CENTRAL GREAT  
BASIN ON MONDAY MORNING. THIS AXIS OF AMPLIFIED FLOW CARVES OUT A  
MODEST TROUGH ACROSS THE SOUTHERN/CENTRAL PLAINS ON TUESDAY AS A  
WAVE OF LOW PRESSURE TRACKS DOWN THE ADJACENT HIGH PLAINS AND  
ACROSS THE RED RIVER. THE PREVIOUS THREE RUNS OF THE GFS AS WELL  
AS THE 00Z ECMWF HAVE SHIFTED TOWARD A MORE AGGRESSIVE SOLUTION AS  
A CYCLONE PUSHES TOWARD THE OH RIVER VALLEY/CENTRAL APPALACHIANS  
ON 07/1200Z. THE 00Z GFS BECOMES A DEEPER OUTLIER BY MIDDAY  
WEDNESDAY WITH A SURFACE PRESSURE OF 993-MB ACROSS NORTHERN NY.  
THE 00Z ENSEMBLE LOW PLOT PACKAGE SHOWS A VAST MAJORITY OF THE  
SOLUTIONS TAKING A TRACK ALONG OR WEST OF THE APPALACHIAN CHAIN  
ALTHOUGH PREVIOUS CYCLES WERE WEAKER OR MORE SPREAD OUT.  
THUS...WOULD EXPECT FUTURE CHANGES IN THE MODELS IN ADDITIONAL  
RUNS. AT THIS TIME...AN UPPER RIDGE REMAINS PARKED OVER THE  
EASTERN PACIFIC AND INTO THE SOUTHWESTERN STATES. SOME  
PERTURBATION IN THE NORTHWESTERLY FLOW TO THE NORTH COULD USHER  
WEAK HEIGHT FALLS INTO SOUTHERN BRITISH COLUMBIA/ALBERTA BY DAY  
7/FEBRUARY 8.  
 
GIVEN ABOVE AVERAGE CONFIDENCE IN THE PATTERN THROUGH DAY  
4/FEBRUARY 5....TOOK A COMPLETE OPERATIONAL MODEL APPROACH  
UTILIZING A COMBINATION OF THE 06Z GFS AND 00Z ECMWF/CMC.  
GRADUALLY INCORPORATED SOME OF THE 06Z GEFS/00Z ECMWF ENSEMBLE  
MEANS IN PLACE OF THE 00Z CMC BEYOND THIS PERIOD GIVEN A SLIGHT  
INCREASE IN MODEL SPREAD. MAINTAINED AT LEAST 40 PERCENT OF AN  
OPERATIONAL COMPONENT THROUGH NEXT WEEK WITH A BIT MORE 00Z ECMWF  
ENSEMBLE MEAN USED GIVEN A DEEPER SURFACE REFLECTION OVER THE OH  
RIVER VALLEY ON WEDNESDAY.  
 
   
..WEATHER HIGHLIGHTS/THREATS
 
 
ABOVE AVERAGE TEMPERATURES WILL BE THE BIG STORY FROM THE ROCKIES  
WESTWARD AS AN ARCTIC BOUNDARY REMAINS BANKED UP AGAINST THE  
MOUNTAINS. GENERALLY SPEAKING...DEPARTURES FROM CLIMATOLOGY SHOULD  
BE ON THE ORDER OF 10 TO 20 DEGREES THROUGHOUT THE PERIOD WITH  
EVEN SOME OVERNIGHT WARMTH BREAKING SOME DAILY RECORDS OVER THE  
WESTERN STATES ON SUNDAY/MONDAY. MEANWHILE...MULTIPLE ARCTIC  
SURGES SHOULD REINFORCE THE COLDER TEMPERATURES INHABITING THE  
CENTRAL/NORTHERN U.S. THE NORTH-CENTRAL STATES CAN EXPECT MORE OF  
THE PERSISTENT COLD WEATHER AS HIGHS WILL BE AROUND 10 TO 20  
DEGREES BELOW AVERAGE. ON SUNDAY...HIGH TEMPERATURES SHOULD  
STRUGGLE TO ESCAPE THE SINGLE DIGITS FROM THE DAKOTAS INTO THE  
UPPER MIDWEST. COOLER WEATHER WILL EXPAND EASTWARD IN TIME BUT  
MODIFY WITH ANOMALIES BEING LESS SIGNIFICANT. ALONG THE EAST  
COAST...A PERIOD OF WARMTH IS LIKELY ON TUESDAY/WEDNESDAY AS  
HEIGHTS BUILD IN ADVANCE OF THE UPSTREAM SYSTEM. THEN A RETURN TO  
TEMPERATURES IN THE 20S AND 30S ARE EXPECTED FROM THE CENTRAL  
APPALACHIANS/MID-ATLANTIC NORTHWARD.  
 
TOWARD THE END OF THE WEEKEND...MODERATE TO LOCALLY HEAVY RAINFALL  
IS POSSIBLE ACROSS THE SOUTHERN/SOUTHEASTERN STATES WITH 24-HOUR  
AMOUNTS AROUND 1 TO 2 INCHES THROUGH 05/0000Z. ANOTHER MAXIMA SETS  
UP OVER UPPER NEW ENGLAND AS THE SURFACE LOW BEGINS TO WIND UP AND  
THE 850-700 MB MOISTURE FLUX ANOMALIES EXCEED 4 SIGMA BY 05/1200Z.  
A SNOWFALL THREAT WILL EXIST WEST OF THE I-95 CORRIDOR WITH A  
GENERAL FOCUS FROM THE UPPER OH VALLEY/CENTRAL APPALACHIANS INTO  
THE LOWER GREAT LAKES AND INTERIOR NEW ENGLAND. CONDITIONS QUIET  
BRIEFLY BEFORE THE NEXT SYSTEM DEEPENS OVER THE SOUTHERN PLAINS.  
BY TUESDAY/WEDNESDAY...HEAVY RAINFALL BREAKS OUT ACROSS THE LOWER  
MS VALLEY INTO THE OZARKS AND MID-SOUTH WITH THE 06Z GFS SHOWING  
THE POTENTIAL FOR 24-HOUR AMOUNTS REACHING THE 2 TO 4 INCH RANGE.  
LIGHTER AMOUNTS ARE EXPECTED DOWNSTREAM WHILE ANOTHER SNOWFALL  
THREAT EXISTS OVER SIMILAR LOCATIONS FROM THE PREVIOUS STORM. THE  
PAIR OF SYSTEMS COULD LEAVE A DECENT SNOWPACK WHEN IT IS ALL SAID  
AND DONE BUT A LOT OF DETAILS CAN CHANGE IN THE UPCOMING DAYS.  
ELSEWHERE...A STRIPE OF PRECIPITATION SHOULD STRETCH FROM THE  
PACIFIC NORTHWEST INTO THE UPPER INTERMOUNTAIN WEST ON  
SUNDAY/MONDAY AS AN EARLIER MENTIONED SHORTWAVE PUSHES THROUGH.  
OROGRAPHICALLY FAVORED LOCATIONS WILL LIKELY SEE THE BETTER QPF  
AMOUNTS WITH SNOW OVER THE HIGHER ELEVATIONS. BEYOND THIS  
PERIOD...LIGHTER AMOUNTS ARE BEING FORECAST...GENERALLY ALONG THE  
QUASI-STATIONARY ARCTIC BOUNDARY STRETCHING FROM THE  
CENTRAL/NORTHERN ROCKIES BACK INTO THE UPPER INTERMOUNTAIN WEST.  
AS A WHOLE...CONDITIONS SHOULD GRADUALLY BECOME DRIER AS HEIGHTS  
BUILD OVERHEAD.  
 
RUBIN-OSTER  
 

 
 
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