EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 825 AM EST SAT JAN 28 2017 VALID 12Z TUE JAN 31 2017 - 12Z SAT FEB 04 2017 OVERVIEW AND GUIDANCE EVALUATION ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE GUIDANCE SHOWED GOOD AGREEMENT IN AN INCREASINGLY STRONG MID-LEVEL HIGH ACROSS AK THAT, COMBINED WITH SYSTEMS MOVING ACROSS THE PACIFIC NEAR THE 40TH PARALLEL, BRINGS A BROAD TROUGH INTO THE EASTERN PACIFIC. DOWNSTREAM, RIDGING BRIEFLY BUILDS ACROSS THE ROCKIES AND A BROAD TROUGH ATTEMPTS TO HANG ON OUT EAST. THE 00Z UKMET STRAYED FROM THE REMAINDER OF THE GUIDANCE WITH THE LOW APPROACHING THE PACIFIC NORTHWEST IN FIVE DAYS (EARLY THURSDAY MORNING), SO COULD NOT USE ITS MASS FIELDS BEYOND WEDNESDAY. FOR THE MOST PART, THE 500 HPA HEIGHTS, PRESSURES, WIND GRIDS WERE BASED ON A COMPROMISE OF THE 00Z CANADIAN, 00Z ECMWF, AND 06Z GFS EARLY ON BEFORE INCLUDING INCREASING AMOUNTS OF THE 00Z ECMWF ENSEMBLE MEAN AND 00Z NAEFS MEAN WITH TIME. THE TEMPERATURES, PRECIPITATION CHANCES, CLOUD, WEATHER, AND DEW POINT GRIDS ARE MORE BASED ON THE ENSEMBLE MEAN GUIDANCE TO BETTER ACCOUNT FOR UNCERTAINTY. THE DAYS 4-7 QPF ARE STARTING WITH A COMPROMISE OF THE 00Z ECMWF AND 06Z GFS, WHICH MAY INCLUDE ELEMENTS OF THE 12Z GFS SHOULD ITS MASS FIELDS HOLD SERVE FROM ITS 06Z RUN. WEATHER HIGHLIGHTS/THREATS ~~~~~~~~~~~~~~~~~~~~~~~~~~ MID TO LATE WEEK, A SLOW MOVING SYSTEM APPROACHING THE WEST WILL BRING A PERIOD OF FOCUSED HEAVY RAIN/HIGHER ELEVATION SNOW TO NORTHERN CA AND THE PACIFIC NORTHWEST, WITH SOME MOISTURE EXTENDING FARTHER INLAND INTO THE GREAT BASIN AND NORTHERN CONTINENTAL DIVIDE. THE NORTHERN ROCKIES/INTERIOR WEST MAY SEE A PERIOD OF ENHANCED PRECIPITATION IN ASSOCIATION WITH A STALLED FRONT AND THE SHEARED ENERGY ALOFT INITIALLY OVER SOUTHWEST CANADA. HIGHER ELEVATIONS WILL SEE SNOW WHILE PRECIPITATION TYPE ELSEWHERE WILL DEPEND ON EXISTENCE/PERSISTENCE OF SUFFICIENTLY COLD LOW LEVEL AIR. EXPECT LOW TEMPERATURES OVER MOST OF THE WEST TO AVERAGE NEAR TO ABOVE NORMAL... WHILE HIGH TEMPS SHOULD TEND TO BE BELOW NORMAL OVER NRN AREAS AND NEAR/ABOVE NORMAL FARTHER SOUTH. AN AREA OF MOSTLY LIGHT TO MODERATE SNOW WILL ACCOMPANY THE GREAT LAKES/NORTHEAST SYSTEM TUESDAY-WEDNESDAY, WITH LAKE EFFECT/ENHANCED PRECIPITATION EXPECTED THROUGH THE PERIOD WITHIN A REGION OF CYCLONIC FLOW. FROM THURSDAY INTO SATURDAY, ONE OR MORE AREAS OF MOISTURE AHEAD OF SUBTLE SHORTWAVES ALOFT STREAMING OVER/EAST OF THE PLAINS MAY GENERATE SOME RAIN OR SNOW DEPENDING ON LATITUDE. THE CENTRAL PLAINS TO MID-ATLANTIC APPEARS TO BE THE MOST LIKELY DIVIDING LINE FOR PRECIPITATION TYPE. POTENTIAL WAVY FRONT OVER THE SOUTHERN PLAINS/MS VALLEY MAY PROVIDE A FOCUS FOR SOME OF THIS ACTIVITY AS WELL. SOUTHERN AREAS SHOULD AVERAGE ABOVE NORMAL FOR TEMPERATURES. FROM THE NORTHERN PLAINS EAST AND SOUTHEAST, EXPECT THE WARMEST READINGS EARLY IN THE PERIOD FOLLOWED BY GENERALLY BELOW NORMAL READINGS. ROTH/RAUSCH