EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 118 AM EST SUN FEB 12 2017 VALID 12Z WED FEB 15 2017 - 12Z SUN FEB 19 2017 ...LAST OF THE TRIFECTA OF SNOWSTORMS FOR THE NORTHEAST WEDNESDAY/THURSDAY... OVERVIEW ~~~~~~~~ ACTIVE PATTERN TO CONTINUE FOR MUCH OF THE LOWER 48, INITIALLY IN THE EAST/SOUTHEAST MID-WEEK AND THEN THROUGH THE WEST AND INTERIOR WEST THURSDAY INTO NEXT WEEKEND. UPPER RIDGING INITIALLY OVER ALBERTA IS FORECAST TO SLIDE SOUTHEASTWARD TOWARD THE GREAT LAKES BY NEXT WEEKEND WHILE TROUGHING TO ITS EAST WHIPS THROUGH THE NORTHEAST INTO ATLANTIC CANADA. IN THE PACIFIC, A STRONG JET BETWEEN ALASKA AND HAWAI'I SHOULD FORCE TROUGHING INTO THE SW STATES AND NW MEXICO LATER NEXT WEEK RIGHT BEHIND A LEAD UPPER LOW THAT WILL SLOWLY BUT STEADILY ROTATE THROUGH NORTHERN MEXICO FROM LATE WEEK INTO THE WEEKEND. MODEL EVALUATION ~~~~~~~~~~~~~~~~~ DIFFERENCES PREVIOUSLY SEEN IN THE NORTHERN STREAM NEAR NEW ENGLAND/ATLANTIC CANADA THE PAST FEW DAYS ARE RESOLVING THEMSELVES, AS THE ECMWF TRENDS QUICKER TOWARDS FORMER GFS/GEFS MEAN SOLUTIONS AND AWAY FROM ESPECIALLY EXTREME SOLUTIONS AT THE SURFACE ACROSS/NEAR NEW ENGLAND. DIFFERENCES OUT WEST IN THE 18Z GFS/12Z ECMWF ARE WITHIN THE BROAD SCOPE OF ENSEMBLE SOLUTIONS. THE UKMET WAS TOO QUICK WITH ENERGY MOVING INTO THE WEST COAST FROM THURSDAY ONWARD. THE 12Z CANADIAN APPEARED USEFUL UNTIL FRIDAY MORNING BEFORE IT TOO BECAME QUICK WITH SYSTEMS IN THE WESTERLIES. FOR FLORIDA, BOTH THE 12Z CANADIAN AND (TO A LESSER DEGREE) THE 12Z ECMWF BRING A SYSTEM FROM THE TROPICS TOWARDS THE STATE ON DAY 7/FEBRUARY 19. THE CANADIAN IS UP TO ITS OLD TRICKS AND DISREGARDED. THE ECMWF DOES THIS WHILE FLATTENING THE NORTHERN STREAM RIDGE NEAR THE US/CANADIAN BORDER WHICH ACCELERATES ENERGY DOWN SOUTH NEAR THE GULF COAST. IN THE QPF REALM, NOW THAT THE 00Z GFS HAS TRENDED TOWARDS A SIMILAR SOLUTION TO THE ECMWF WITH THE UPPER LOW, PLACED SOME STOCK IN THE ECMWF SOLUTION ACROSS THE FL PENINSULA. GUIDANCE PREFERENCES ~~~~~~~~~~~~~~~~~~~~ THE PRESSURES/500 HPA HEIGHTS/WIND GRIDS STARTED WITH A COMPROMISE OF THE 12Z UKMET/12Z CANADIAN/18Z GFS/12Z ECMWF FOR WEDNESDAY INTO THURSDAY MORNING BEFORE SWITCHING TO A 12Z CANADIAN/18Z GFS/12Z ECMWF SOLUTION THURSDAY INTO FRIDAY MORNING, AND THEN USING AN INCREASING AMOUNT OF 12Z ECMWF AND 12Z NAEFS ENSEMBLE MEAN INFORMATION THEREAFTER IN CONCERT WITH THE 18Z GFS/12Z ECMWF TO DEAL WITH PROBLEMATIC DETAILS, PARTICULARLY IN THE 12Z ECMWF FORECAST. THE TEMPERATURE/DEW POINT/CLOUD/WEATHER/PRECIPITATION CHANCE GRIDS WERE MORE ENSEMBLE MEAN HEAVY IN ORDER TO BETTER TAKE INTO ACCOUNT THE UNCERTAINTY. FOR DAYS 4-7, A COMPROMISE OF THE 12Z ECMWF/18Z GFS/00Z GFS WAS USED FOR THE PRECIPITATION EXPECTED. WEATHER HIGHLIGHTS/THREATS ~~~~~~~~~~~~~~~~~~~~~~~~~~ THE EJECTING UPPER LOW ACROSS THE SOUTHERN TIER OF THE COUNTRY WILL GENERATE ENHANCED AREAS OF RAIN ACROSS THE FL PENINSULA EARLY. A POTENTIALLY ROBUST NOR'EASTER ON WEDNESDAY/THURSDAY MAY MAKE FOR WINDY/SNOWY CONDITIONS IN ESPECIALLY EASTERN NEW ENGLAND WITH NW FLOW BEHIND IT OVER THE EASTERN LAKES (MODEST LAKE EFFECT SNOW) INTO THE CENTRAL APPALACHIANS. THE NEXT PACIFIC CYCLONE OFF THE COAST THURSDAY AND POSSIBLY ONSHORE FRIDAY SHOULD GET CLOSE ENOUGH TO PRODUCE WIDESPREAD PRECIPITATION FROM NORTHERN CA NORTH ACROSS OR AND WA, EVENTUALLY EXTENDING INLAND INTO THE NORTHERN ROCKIES AND TERRAIN IN AND NEAR THE GREAT BASIN, SOUTHWEST, AND CENTRAL ROCKIES. THE NORTHERN PLAINS AND UPPER MS VALLEY SHOULD SEE ABOVE NORMAL TEMPERATURES AS THE DEEP LAYER RIDGE OUT WEST WITH ABOVE NORMAL MID-LEVEL HEIGHTS STARTS DRIFTING EAST INTO THE HIGH PLAINS. ABOVE NORMAL TEMPERATURES ACROSS A WIDE PORTION OF THE ROCKIES/GREAT BASIN/SOUTHWEST US. LATE IN THE PERIOD, COOLING IS EXPECTED NEAR THE WEST COAST AS THE FRONTAL ZONE MARCHES THROUGH THE INTERMOUNTAIN WEST AND MID-LEVEL HEIGHTS FALL BELOW AVERAGE. DESPITE THE EXPECTED TROUGHING ACROSS THE NORTHEAST AND SOMEWHAT BELOW NORMAL 500 HPA HEIGHTS THROUGH THE PERIOD, TEMPERATURES SHOULD BE ROUGHLY NEAR SEASONAL NORMS FOR MUCH OF THE EAST, WITH A SHORT BOUT OF BELOW NORMAL TEMPERATURES FROM THE MID-SOUTH INTO THE SOUTHEAST THURSDAY INTO FRIDAY. ROTH/FRACASSO