EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1106 AM EST FRI FEB 17 2017 VALID 12Z MON FEB 20 2017 - 12Z FRI FEB 24 2017 ...PATTERN OVERVIEW/MODEL EVALUATION/PREFERENCES... AN ACTIVE PATTERN WILL CONTINUE WITH LARGE-SCALE AMPLIFICATION EVIDENT IN THE 500-MB HEIGHT FIELDS. MODELS AGREE ON SPLIT FLOW WITH A POTENT SOUTHERN STREAM CLOSED LOW BARRELING THROUGH THE GULF OF MX DURING THE TUESDAY THROUGH THURSDAY TIMEFRAME. GIVEN THE ANOMALOUS NATURE OF THE PATTERN...WELL ESTABLISHED ANOMALIES ARE SUGGESTED IN THE GUIDANCE. MORE SPECIFICALLY...SUCH VALUES RANGE FROM 2 TO 2.5 SIGMA ABOVE AVERAGE FOR BOTH THE CLOSED LOW AS WELL AS THE DOWNSTREAM RIDGING WHICH EXTENDS UP INTO EASTERN CANADA. ACROSS THE WESTERN U.S...AN EXPANSIVE LONGWAVE TROUGH WILL CARRY A SERIES OF SHORTWAVES INTO NORTHERN/CENTRAL CA WHICH CARRIES A THREAT FOR ADDITIONAL HEAVY PRECIPITATION TO THE REGION. THIS INITIAL SURGE SHOULD GRADUALLY DAMPEN AS THE PERTURBATIONS IN THE FLOW FLATTEN DOWNSTREAM. HOWEVER...ANOTHER MORE IMPRESSIVE BAND OF HEIGHT FALLS DIG INTO THE SOUTHWESTERN U.S. BY THE MIDDLE OF NEXT WEEK. THERE ARE STRONG INDICATIONS THIS SYSTEM WILL CONTINUE ADVANCING EASTWARD WITH A RATHER POTENT UPPER LOW SPINNING ACROSS THE CENTRAL PLAINS/MIDDLE MS VALLEY BY 24/1200Z. ONE NOTABLE TREND IN THE GUIDANCE HAS BEEN TO SPEED UP WITH THE CLOSED LOW EMERGING OUT OF EASTERN MX. WHILE IN RECENT DAYS THE TREND HAD BEEN TO SLOW THE SYSTEM DOWN...THERE HAS BEEN A MOVE TOWARD MORE AMPLIFICATION IN THE NORTHERN STREAM WHICH HELPS USHER THE GULF OF MX FEATURE MORE QUICKLY TOWARD THE EAST. INTERESTINGLY...THE PREVIOUS QUICKER CMC SUITE MOVED TOWARD A MUCH SLOWER SOLUTION WHICH MIMICS WHAT HAD BEEN SEEN BY THE GFS/ECMWF CAMPS IN RECENT DAYS. GIVEN ENSEMBLE SPAGHETTI PLOTS HAVE SHOWN MORE CONFIDENCE IN MORE AMPLIFIED FLOW ACROSS THE NORTHERN STREAM...THINKING THE SLIGHTLY QUICKER PROGRESSION LOOKS MORE REASONABLE AT THIS TIME. A COUPLE OF SOLUTIONS STARTED TO LOOK A LITTLE OUTLYING TOWARD THE LATTER HALF OF THE MEDIUM RANGE PERIOD. IN PARTICULAR...THE 00Z ECMWF TAKES THE CLOSED LOW INTO WESTERN CUBA ON THURSDAY MORNING WHICH IS WELL SOUTH OF ALL ENSEMBLE MEMBERS DEPICTED IN THE 570-DM SPAGHETTI PLOT. LIKEWISE...THE 06Z GFS IS ONE OF THE QUICKEST SOLUTIONS AND SHOWED A 1000-MB SURFACE LOW MOVING INTO THE FL KEYS. LOOKING TOWARD THE END OF FORECAST...THE SIGNAL FOR RAPID CYCLOGENESIS OFF THE LEE OF THE ROCKIES AND INTO THE CENTRAL PLAINS IS QUITE STRONG. FOR A DAY 7 FORECAST...ENSEMBLE SCATTER LOW PLOTS GENERALLY CLUSTER AROUND THE NE/KS/IA/MO BORDER. FORECAST 500-MB HEIGHT ANOMALIES ARE AROUND THE 2 TO 2.5 SIGMA BELOW CLIMATOLOGY RANGE WHICH SUGGESTS A PRETTY SIGNIFICANT STORM IS LIKELY TO AFFECT THIS REGION LATE IN THE WORK WEEK. AS MENTIONED EARLIER...CHOSE TO NOT INCLUDE THE 06Z GFS NOR THE 00Z ECMWF GIVEN THE ISSUES WITH THE HANDLING OF THE CLOSED LOW CROSSING THE GULF OF MX. INSTEAD...PREFERRED TO STICK CLOSER TO THE 00Z GFS/GEFS MEAN AS WELL AS THE PREVIOUS 12Z ECMWF/MORE RECENT 00Z ECMWF ENSEMBLE MEAN. LIKED THE 00Z CYCLE OF THE ECMWF ENSEMBLES AS IT GAVE THE DEFINITION NECESSARY ON DAY 7 TO ACCOUNT FOR THE DEEP SURFACE CYCLONE EXITING THE GREAT PLAINS. GENERALLY FOLLOWED A COMBINATION OF THESE SOLUTIONS WITH DECREASING AMOUNTS OF DETERMINISTIC INFLUENCE TOWARD THE DAY 6/7 TIMEFRAME. FURTHER...DID INCORPORATE THE OVERNIGHT CONTINUITY INTO THE MIX...PARTICULARLY AS IT AGREED WITH THE THINKING THIS MORNING. ...WEATHER HIGHLIGHTS/THREATS... INITIALLY...THE BIGGEST PRECIPITATION THREATS WILL BE ALONG THE CENTRAL/EASTERN GULF COAST...PERHAPS EXTENDING NORTHWARD AWAY FROM THE COAST AS WELL AS ACROSS THE WESTERN STATES. THIS IS ESPECIALLY THE CASE ACROSS NORTHERN/CENTRAL CA WHICH HAS SEEN PLENTY OF RAIN/SNOW DURING THIS WINTER SEASON. EVENTUALLY THE FORMER SYSTEM EXITING THE GULF COAST MAY BRING A THREAT FOR HEAVY RAINFALL ALONG THE CAROLINA COAST DEPENDING ON THE EVENTUAL TRACK OF THE UPPER LOW. ELSEWHERE...EXPECT AN UPTICK IN PRECIPITATION ACROSS THE CENTRAL TO NORTHERN PLAINS AND INTO THE MIDDLE/UPPER MS VALLEYS GIVEN THE INTENSIFYING SURFACE LOW. OF COURSE WINTRY PRECIPITATION IS LIKELY GIVEN HOW DYNAMIC THIS SYSTEM WILL BE. EXCEPT FOR THE WESTERN U.S. AND EVENTUALLY THE CENTRAL/NORTHERN PLAINS ON DAY 7...MUCH OF THE REGION CAN EXPECT WELL ABOVE NORMAL TEMPERATURES TO DOMINATE. IN FACT...PLENTY OF DAILY TEMPERATURE RECORDS MAY BE BROKEN...BOTH FOR HIGHS AS WELL AS THE WARM OVERNIGHT LOWS. THE CURRENT FORECAST SUGGESTS HIGHS WELL INTO THE 60S ON MONDAY ACROSS IA WITH UPPER 50S AS FAR NORTH AS THE MINNEAPOLIS/ST. PAUL AREA. MEANWHILE...OVERNIGHT LOWS ON MONDAY/TUESDAY SHOULD BE IN THE 40S ACROSS MUCH OF THE NORTH-CENTRAL U.S. WHICH EQUATES TO ANOMALIES IN THE 20 TO 30 DEGREE ABOVE CLIMATOLOGY RANGE. RUBIN-OSTER