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Medium Range Products Valid On:
03/14/2017
Day 7 Fronts/Pressures (valid 12Z)
Day 6 Fronts/Pressures(valid 12Z)
Day 5 Fronts/Pressures(valid 12Z)
Day 4 Fronts/Pressures(valid 12Z)
Day 3 Fronts/Pressures(valid 12Z)
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12Z Analysis on 03/14/2017 (verification)
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Day 7 Minimum Temperatures
(morning minimum temperatures valid on 03/14/2017)
Day 6 Minimum Temperatures
(morning minimum temperatures valid on 03/14/2017)
Day 5 Minimum Temperatures
(morning minimum temperatures valid on 03/14/2017)
Day 4 Minimum Temperatures
(morning minimum temperatures valid on 03/14/2017)
Day 3 Minimum Temperatures
(morning minimum temperatures valid on 03/14/2017)
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Day 7 Maximum Temperatures
(afternoon maximum temperatures valid on 03/14/2017)
Day 6 Maximum Temperatures
(afternoon maximum temperatures valid on 03/14/2017)
Day 5 Maximum Temperatures
(afternoon maximum temperatures valid on 03/14/2017)
Day 4 Maximum Temperatures
(afternoon maximum temperatures valid on 03/14/2017)
Day 3 Maximum Temperatures
(afternoon maximum temperatures valid on 03/14/2017)
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Day 7 12-Hr Probability of Precipitation
(valid at 12Z on 03/14/2017)
Day 6 12-Hr Probability of Precipitation
(valid at 12Z on 03/14/2017)
Day 5 12-Hr Probability of Precipitation
(valid at 12Z on 03/14/2017)
Day 4 12-Hr Probability of Precipitation
(valid at 12Z on 03/14/2017)
Day 3 12-Hr Probability of Precipitation
(valid at 12Z on 03/14/2017)
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Day 7 12-Hr Probability of Precipitation
(valid at 00Z on 03/15/2017)
Day 6 12-Hr Probability of Precipitation
(valid at 00Z on 03/15/2017)
Day 5 12-Hr Probability of Precipitation
(valid at 00Z on 03/15/2017)
Day 4 12-Hr Probability of Precipitation
(valid at 00Z on 03/15/2017)
Day 3 12-Hr Probability of Precipitation
(valid at 00Z on 03/15/2017)
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(Day 7 PMDEPD: Valid 03/10/2017 to 03/14/2017)
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1111 AM EST TUE MAR 07 2017
VALID 12Z FRI MAR 10 2017 - 12Z TUE MAR 14 2017
...PATTERN OVERVIEW AND MODEL EVALUATION...
THE LARGE SCALE PATTERN WAS FAIRLY CONSISTENT AMONGST GUIDANCE
WITH NEARLY FLAT/ZONAL FLOW TO SLIGHT RIDGING IN THE WEST AND A
TROUGH IN THE EAST...HOWEVER DIFFERENCES IN THE TIMING AND
AMPLITUDE OF THE SHORTWAVES MOVING THROUGH THE PACIFIC NORTHWEST,
THE GREAT LAKES AND WHETHER OR NOT A WAVE DEVELOPS ALONG THE
SOUTHEAST COAST BY THE END OF THE FORECAST PERIOD KEEPS CONFIDENCE
LOW ON THE SPECIFICS WITH EACH FEATURE.
A SIGNIFICANT FOCUS OF THE FORECAST WILL BE ON THE EVOLUTION OF
EASTERN U.S. LOW PRESSURE DURING THE WEEKEND. SUPPORTING ENERGY
IS FORECAST TO REACH THE PACIFIC NORTHWEST COAST AROUND THE START
OF THE PERIOD EARLY FRIDAY AND THEN HEAD INTO THE EASTERN U.S.
MEAN TROUGH. THE WEAK NATURE OF THIS ENERGY AND THE FACT IT IS
EMBEDDED WITHIN PROGRESSIVE FLOW WOULD TEND TO SUPPORT BELOW
AVERAGE PREDICTABILITY SEVERAL DAYS OUT IN TIME. THIS IS
REFLECTED BY CURRENT MODEL AND ENSEMBLE SPREAD AS WELL AS
MEANINGFUL RUN TO RUN TRENDS WITH THE LATITUDE OF THE SURFACE
SYSTEM. LATEST TRENDS HAVE GENERALLY BEEN TOWARD A MORE
SUPPRESSED/SOUTHERN TRACK. HOWEVER THE FACT THAT THE SHORTWAVE
ENERGY IS HEADING INTO A MEAN TROUGH KEEPS THE DOOR OPEN FOR A
SLIGHTLY STRONGER SHORTWAVE AND REVERSAL OF THE TREND. THUS AN
INTERMEDIATE SOLUTION SEEMS MOST REASONABLE. LATE IN THE MEDIUM
RANGE PERIOD...DETERMINISTIC GUIDANCE...ESPECIALLY THE
GFS...CONTINUES TO FLIP-FLOP WITH THE EVOLUTION OF SHORTWAVE
ENERGY POSSIBLY PROGRESSING SOUTHEASTWARD OUT OF THE PACIFIC
NORTHWEST ON SUNDAY AND POTENTIAL ASSOCIATED SURFACE CYCLONE
DEEPENING OVER THE CENTRAL PLAINS ON MONDAY.
THE WPC DAY 3-7 FORECAST BEGAN WITH AN INITIAL COMBINATION OF THE
THE 00Z ECWMF/GFS/CMC AND GEFS/ECMWF ENSEMBLE MEANS...WITH
SLIGHTLY MORE WEIGHT GIVEN TO THE PREVIOUS WPC FORECAST AND THE
ECMWF/ECMWF ENSEMBLE MEAN SINCE THEY HAVE BEEN MORE CONSISTENT
WITH THE LARGE SCALE FLOW PATTERN OVER THE PAST FEW MODEL CYCLES.
...WEATHER HIGHLIGHTS...
MUCH OF THE THE NORTHERN TIER STATES WILL REMAIN VERY CHILLY INTO
THE WEEKEND ONCE AN ARCTIC AIRMASS PLUNGES THROUGH THE REGION AND
SETTLES IN OVER THE CENTRAL AND EASTERN U.S. MANY LOCATIONS ACROSS
THE NORTHERN PLAINS AND UPPER MIDWEST WILL HAVE MAXIMUM
TEMPERATURES RANGING 10 TO 20 DEGREES COOLER THAN SEASONAL
AVERAGES...AND IN SOME INSTANCES... NEARLY 25 DEGREES COOLER.
AFTERNOON HIGHS WILL GENERALLY BE IN THE SINGLE DIGITS AND TEENS.
BELOW NORMAL TEMPERATURES EXPECTED TO REACH AS FAR SOUTH AS THE
TENNESSEE VALLEY AND CAROLINAS ON SUNDAY.
THUNDERSTORMS...MODERATE TO HEAVY RAIN...AND ACCUMULATING
SNOW...WILL BE POSSIBLE AS MOISTURE ADVECTION INCREASES AHEAD OF
SURFACE CYCLONE EXPECTED TO DEEPEN ALONG THE LEADING COLD FRONT
AND TRACK FROM THE SOUTHERN PLAINS TO THE MID-ATLANTIC COAST THIS
WEEKEND. EMBEDDED AREAS OF MODERATE TO HEAVY PRECIPITATION WILL BE
POSSIBLE WITH AN UPSTREAM SHORTWAVE AND SURFACE LOW POTENTIALLY
DEEPENING OVER THE CENTRAL PLAINS ON MONDAY...BUT THE DETAILS OF
THE FORECAST REMAIN UNCERTAIN.
NEARLY CONTINUOUS ONSHORE FLOW COMBINED WITH A SERIES OF SHORTWAVE
ENERGY PASSING THROUGH WILL KEEP MUCH OF THE PACIFIC NORTHWEST IN
AN ACTIVE WET PATTERN. PERIODS OF HEAVY RAIN AND MOUNTAIN SNOW TO
THE FAVORED TERRAIN OF THE PACIFIC NORTHWEST AND NORTHERN ROCKIES
IS FORECAST FOR THE END OF THE WORK WEEK AND THIS WEEKEND. MUCH OF
THE DESERT SOUTHWEST...CENTRAL GREAT BASIN AND THE SOUTHERN
ROCKIES WILL REMAIN FAIRLY DRY AND WARM OVER THE NEXT SEVERAL
DAYS. IN FACT... WARMER THAN AVERAGE TEMPERATURES ARE EXPECTED
FROM THE SOUTHWEST TO THE SOUTHEAST WITH DAILY HIGHS RANGING FROM
THE 60S TO MID-TO-UPPER 80S. A FEW LOCATIONS MAY REACH OR EXCEED
DAILY TEMPERATURE RECORDS.
CAMPBELL/RAUSCH/GERHARDT
(Day 6 PMDEPD: Valid 03/11/2017 to 03/15/2017)
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1059 AM EST WED MAR 08 2017
VALID 12Z SAT MAR 11 2017 - 12Z WED MAR 15 2017
...PATTERN OVERVIEW AND MODEL EVALUATION...
OVER THE NEXT WEEK NEARLY ZONAL/FLAT FLOW OVER THE WEST WILL
TRANSITION TO A RIDGE WHICH WILL AMPLIFY THE TROUGH DOWNSTREAM
OVER THE CENTRAL AND EASTERN U.S. THIS IS WELL SUPPORTED IN THE
MOST CURRENT GUIDANCE. PERSISTENT RUN TO RUN VARIABILITY OVER THE
PAST FEW DAYS HAVE NOT IMPROVED CONFIDENCE ON THE SPECIFICS FOR
EMBEDDED SHORTWAVES IN THE PROGRESSIVE FLOW. HOWEVER...THE 00Z/06Z
GFS HAS TRENDED TOWARD A MORE PROGRESSIVE/AMPLIFIED TROUGH DIGGING
INTO THE UPPER MIDWEST BY EARLY SUNDAY MORNING. AS IT SWINGS
THROUGH THE GREAT LAKES/OHIO VALLEY MONDAY INTO THE MEAN TROUGH IT
IS SIGNALING SUPPORT FOR THE DEVELOPMENT/STRENGTHENING OF A
COASTAL SYSTEM BY THE END OF THE PERIOD. THE ECWMF ALSO DEPICTS A
COASTAL SYSTEM...BUT PLACED FARTHER UP THE COAST TO THE SOUTH OF
MAINE. ALTHOUGH MODELS ARE STARTING TO CONVERGE ON THIS SIGNAL
QUITE OF BIT OF SPREAD IS PRESENT WITH THE LOW PLACEMENT AND DEPTH
OF THE PRESSURE CENTER...WHICH WILL AFFECT HOW CLOSE TO THE
COASTLINE OR OUT OVER THE ATLANTIC THE SYSTEM WILL TRACK. THIS
SYSTEM COULD POTENTIALLY BRING LATE SEASON SNOW, POSSIBLY WITH
HIGHER SNOWFALL AMOUNTS, FROM THE MID-ATLANTIC TO NEW ENGLAND.
THE WPC DAY 3-7 FORECAST STARTED WITH A BLEND OF THE 00/06Z
GFS/GEFS MEAN AND 00Z ECMWF/ECWMF ENSEMBLE MEAN...WITH MORE
OPERATIONAL MODEL WEIGHTING EARLY IN THE PERIOD. THIS SOLUTION
SEEMED TO BEST TAKE INTO ACCOUNT THE SOUTHWARD TREND IN THE
GUIDANCE WITH THE LOW TRACKING OFF THE SOUTHEAST COAST ON SUNDAY
WHILE ALSO NOT STRAYING TOO FAR FROM THE PREVIOUS WPC FORECAST.
MORE EVEN MODEL/ENSEMBLE WEIGHT WAS USED TOWARD THE ENSEMBLE MEANS
BY THE DAY 6/7 FORECAST (TUESDAY/WEDNESDAY) SINCE THERE REMAINS A
LARGE AMOUNT OF SPREAD AMONG DETERMINISTIC GUIDANCE WITH THE
SHORTWAVE POSSIBLY AMPLIFYING OVER THE EASTERN U.S. EARLY NEXT
WEEK.
...WEATHER HIGHLIGHTS...
OVER THE COURSE OF THE WEEKEND/THIS COMING WEEK TEMPERATURES WILL
BE ABOVE NORMAL IN THE WEST... WITH BELOW OR WELL-BELOW NORMAL
EAST OF THE CONTINENTAL DIVIDE. AN ARCTIC AIRMASS WILL SETTLE IN
OVER MUCH OF THE CENTRAL AND EASTERN STATES RESULTING IN AFTERNOON
TEMPERATURES FORECAST RANGING 10 TO 30 DEGREES COOLER THAN THOSE
TYPICAL FOR EARLY/MID-MARCH. A FEW LOCATIONS ACROSS NEW ENGLAND
POTENTIALLY COULD SET NEW LOW MAXIMUM TEMPERATURE RECORDS ON
SATURDAY. FOR THE WEST...TEMPERATURES WILL RANGE 5 TO 20 DEGREES
ABOVE NORMAL -- OVERNIGHT TEMPERATURE RECORDS MAY BE BROKEN FOR
SEVERAL LOCATIONS ACROSS SOUTHERN CALIFORNIA/THE GREAT
BASIN/DESERT SOUTHWEST. TEMPERATURES SHOULD BEGIN TO MODERATE
ACROSS THE CENTRAL U.S. EARLY NEXT WEEK AS UPPER RIDGING IN THE
WEST GRADUALLY EDGES EAST.
IN TERMS OF PRECIPITATION ACROSS THE NATION...MODERATE TO HEAVY
RAINS WITH EMBEDDED THUNDERSTORMS ARE EXPECTED WITHIN WARM
ADVECTION INCREASING AHEAD A SHORTWAVE AND SURFACE LOW TRACKING
FROM THE SOUTHERN PLAINS TO THE SOUTHEAST COAST SATURDAY INTO
SUNDAY...WITH LATE SEASON SNOW POSSIBLE ON THE NORTHERN EDGE OF
THE PRECIPITATION SHIELD. MODERATE TO HEAVY PRECIPITATION WILL
ALSO BE POSSIBLE WITH AN UPSTREAM SHORTWAVE EJECTING OUT INTO THE
NORTH CENTRAL U.S. ON MONDAY...ESPECIALLY IF IT HELPS DEEPEN A
SURFACE CYCLONE ALONG THE EASTERN SEABOARD TUESDAY/WEDNESDAY...BUT
THE DETAILS OF THE FORECAST REMAIN EXTREMELY UNCERTAIN. COASTAL
RAIN AND HIGHER ELEVATION SNOW...WITH PERIODS OF HIGHER
INTENSITY...WILL SPAN FROM THE PACIFIC NORTHWEST TO THE NORTHERN
ROCKIES FOR SEVERAL DAYS.
CAMPBELL/GERHARDT
(Day 5 PMDEPD: Valid 03/12/2017 to 03/16/2017)
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1057 AM EST THU MAR 09 2017
VALID 12Z SUN MAR 12 2017 - 12Z THU MAR 16 2017
...PATTERN OVERVIEW AND MODEL EVALUATION...
A RIDGE OVER THE WEST/ADJACENT HIGH PLAINS AND TROUGH OVER THE
EAST WILL BE THE MEAN SYNOPTIC PATTERN THROUGH THE EXTENDED
PERIOD... BECOMING MORE AMPLIFIED MONDAY ONWARD
WITH POTENTIAL MULTIPLE DIPS IN UPPER JETS AND POSSIBLE PHASING
FOR A RETURN TO WINTER. WPC FAVORED A SOLID BLEND OF THE 00/06Z
GFS/GEFS AND 00Z ECMWF/EC MEAN THROUGHOUT MOST OF THE FORECAST
PERIOD.
...WEATHER HIGHLIGHTS...
TEMPERATURES ARE FORECAST TO REMAIN ABOVE AVERAGE ACROSS MUCH OF
THE WEST AND BELOW OR WELL-BELOW AVERAGE IN THE EAST. FOR AREAS
PRIMARILY WEST OF THE ROCKIES...THE 5 DAY MAXIMUM MEAN TEMPERATURE
FORECAST SHOW AFTERNOON HIGHS OF +5 TO +15 DEGREES WITH THE
HIGHEST ANOMALIES OVER THE CENTRAL/SOUTHERN GREAT BASIN AND
EASTERN COLORADO. FROM THE DAKOTAS TO TEXAS AND AREAS EAST...THE 5
DAY MEAN TEMPERATURE FORECAST WILL RANGE FROM -5 TO -20 DEGREES.
THE COOLEST AREAS WILL LIKELY BE THE MIDWEST AND OHIO
VALLEY/CENTRAL APPALACHIANS.
MULTIPLE WAVES OF PRECIPITATION IS EXPECTED FOR THE PACIFIC
NORTHWEST FOR SEVERAL DAYS. COASTAL AREAS AND VALLEYS WILL HAVE
RAIN, POSSIBLY HEAVY AT TIMES, AND SNOW FOR THE HIGHER ELEVATIONS
OF THE NORTHERN CASCADES AND THE NORTHERN ROCKIES. MODERATE TO
HEAVY RAINS WITH EMBEDDED THUNDERSTORMS IS EXPECTED ALONG THE
CENTRAL/EASTERN GULF COAST AND THE SOUTHEAST...WITH A SLIGHT
PROBABILITY OF SNOW ACROSS NORTH CAROLINA NEAR THE NORTHERN EXTENT
OF THE PRECIP SHIELD. LIGHT TO MODERATE SNOW WILL BE POSSIBLE FOR
THE EASTERN DAKOTAS/UPPER MIDWEST AS A SHORTWAVE TROUGH DIGS
THROUGH THE CENTRAL U.S. ON SUNDAY... SPREADING ACROSS THE OHIO
AND TENNESSEE VALLEYS/APPALACHIANS ON MONDAY.
THE UPPER DYNAMICS WILL BEGIN TO TRANSFER TO THE MID-ATLANTIC
COAST ON MONDAY FOR FRONTOGENESIS AND POSSIBLE BURST IN QPF. FOR
TUESDAY AND BEYOND... A POSSIBLE AXIS OF SIGNIFICANT SNOWFALL WITH
RAPID SURFACE CYCLOGENESIS WILL BE THE FOCUS FROM THE MID-ATLANTIC
COAST TO NEW ENGLAND. OVERNIGHT BOTH THE OPERATIONAL GFS AND ECMWF
SUGGESTED THE HEAVIEST AXIS ALONG OR JUST EAST OF THE I95 CORRIDOR
FROM PHL/NYC TO BOS.... WHEREAS THE GUIDANCE FROM THIS MORNING
SUGGESTED A SLIGHT SHIFT TO THE EAST. THE LATE WINTER STORM WILL
SLOWLY DEPART NEW ENGLAND BY THE END OF THE PERIOD. A STRONG
FRONTAL ZONE MOVES INTO THE NORTHER TIER OF THE COUNTRY FOR
RAIN/MTN SNOW BY MIDWEEK.
CAMPBELL
(Day 4 PMDEPD: Valid 03/13/2017 to 03/17/2017)
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1017 AM EST FRI MAR 10 2017
VALID 12Z MON MAR 13 2017 - 12Z FRI MAR 17 2017
...WINTER AIN'T OVER TILL IT'S OVER...
...OVERVIEW...
A POTENTIALLY SIGNIFICANT LATE-WINTER STORM IS FORECAST TO DEVELOP
OFF THE MID-ATLANTIC COAST EARLY NEXT WEEK AND TRACK JUST OFF THE
NEW ENGLAND COAST. VERY COLD AIR FOR MID-MARCH WILL ACCOMPANY THE
NOR'EASTER AND WILL LINGER THROUGH THE WEEK. THE SOUTHWEST WILL BE
MUCH QUIETER (AND WARM) WHILE THE PACIFIC NORTHWEST WILL SEE A
COUPLE SYSTEMS PUSH THROUGH.
...GUIDANCE PREFERENCES AND EVALUATION...
A BLEND OF THE 06Z GFS AND A COMBINATION OF THE 00Z ECMWF AND 00Z
EC MEAN WAS USED. THE OVERALL TREND WITH THE NOR'EASTER WAS A
SLIGHT NORTHWESTWARD SHIFT IN THE STORM TRACK. THE 00Z GFS AND TO
A LESS EXTENT THE 06Z RUN WERE ON THE WESTERN PORTION OF THE
ENSEMBLE SPREAD...TAKING THE LOW CENTER INTO NEW ENGLAND WITH A
990 MB LOW. THE ECMWF/CANADIAN MODELS WERE TRACKING JUST OFF THE
NEW ENGLAND COAST NEAR THE BENCHMARK AND A DEEPER LOW. THE ECMWF
WAS THE MOST AGGRESSIVE WITH A SUB 975 MB LOW. THE 500 MB PATTERN
IS IN GOOD ENOUGH AGREEMENT OVERALL BUT DETAILS IN THE EVOLUTION
AND INTERACTION OF SHORTWAVE ENERGY ROTATING AROUND THE EASTERN
U.S. TROUGH LEAD TO MODEST DIFFERENCES IN THE SURFACE LOW
FORECAST. CONFIDENCE IS RATHER HIGH FOR A MAJOR STORM SYSTEM TO
DEVELOP OFF THE EAST COAST BUT DIFFERENCES IN THE SURFACE FEATURES
MAKE THE SENSIBLE WEATHER IMPACTS MORE UNCERTAIN AT THIS TIME.
FROM THE PREVIOUS DISCUSSION..
MAIN EVENT WILL BE IN THE NORTHEAST EARLY NEXT WEEK (TUE INTO
WED... PI DAY AND THE IDES OF MARCH). DESPITE THE EARLY TASTE OF
SPRING FOR MUCH OF THE EAST IN FEBRUARY AND EARLY MARCH, WINTER
APPEARS TO BE READY FOR A COMEBACK. THE MODELS/ENSEMBLES HAVE
MOSTLY CONVERGED ON A RAPIDLY DEEPENING STORM ON TUESDAY, THOUGH
THE EVOLUTION REMAINS COMPLICATED. IN ADDITION, EARLIER RUNS WERE
NOT AS ROBUST SO NOTHING IS SET IN STONE.
THE SETUP IS NOT YOUR CLASSIC MILLER TYPE-A OR TYPE-B STORM BUT
SEEMINGLY A COMBINATION OF THE TWO -- THERE IS FORECAST TO BE AN
ALREADY-DEFINED SURFACE LOW OFF THE GA COAST LATE MONDAY (VERY
MILLER TYPE-A) IN ADDITION TO AN UPSTREAM CLIPPER MOVING THROUGH
THE OHIO VALLEY (LIKE A MILLER TYPE-B). HOW THE UPPER TROUGH
SWINGS THROUGH THE MIDWEST WILL DETERMINE HOW THE DOMINANT LOW
TRACKS -- IT COULD BE TUGGED FARTHER WEST BY A STRONGLY DIGGING
TROUGH OR BE LEFT TO SWING FARTHER EAST. THIS IS ONE OF THOSE
SITUATIONS WHERE THE SPREAD OF POSSIBILITIES IS NECESSARILY LARGE,
ENCOMPASSING NEARLY ALL SCENARIOS FROM A LIGHT/MINOR EVENT TO AN
OUTRIGHT BLIZZARD, DEPENDING ON YOUR LOCATION.
ECMWF/CANADIAN LIED ON THE MORE EXTREME SIDE OF THE ENSEMBLE
SPREAD (BUT WITHIN THE ENVELOPE) AS THEY MAINTAINED TWO SEPARATE
UPPER LOWS DUMBBELLING THROUGH THE NORTHEAST. THE GFS RUNS WERE
MORE COHERENT BUT STILL SHOWED SEPARATED VORTICITY SWINGING
NORTHEASTWARD AHEAD OF THE UPPER LOW. SUFFICE IT TO SAY, THE
MODELS WILL NOT GET THE DETAILS RIGHT AT THIS TIME RANGE, SO
DETERMINISTIC SUCCESS IS FUTILE. RATHER, THE RANGE OF SCENARIOS
SHOULD BE KEPT IN MIND.
ONCE THIS SYSTEM LIFTS INTO ATLANTIC CANADA, MODELS DIVERGE IN HOW
TO HANDLE THE UPSTREAM RIDGE OVER THE SOUTHWEST (STRONGER VS
FLATTER). THIS HAD BIGGER IMPLICATIONS FOR TEMPERATURES OVER THE
SOUTHERN PLAINS BUT ALSO FOR PRECIPITATION (GFS/GEFS WETTER THAN
THE ECMWF/ECMWF ENSEMBLES). MUCH FARTHER UPSTREAM, THE NORTHEAST
PACIFIC WILL BE DIFFICULT TO ACCURATELY FORECAST WITH SEVERAL
IMPULSES MOVING TOWARD SW CANADA AND THE NW CONUS.
...WEATHER HIGHLIGHTS...
WARM WEATHER WILL HOLD IN THE WEST AS UPPER RIDGING HELPS
TEMPERATURES TO ABOVE AVERAGE VALUES (BY ABOUT 10-20F WHICH WILL
TAKE DESERT AREAS INTO THE 90S AND NEAR RECORD HIGHS). THAT WILL
MOVE SLIGHTLY EASTWARD BY LATER NEXT WEEK INTO THE CENTRAL PLAINS.
THE EAST WILL BE WELL BELOW AVERAGE (15-25F BELOW CLIMO) WITH
TEMPERATURES IN THE 30S IN THE MID-ATLANTIC AND TEENS/LOW 20S INTO
W NC AND SW VA. SHOULD TAKE UNTIL NEXT WEEKEND TO GET BACK TOWARD
MORE TYPICAL VALUES FOR MID-MARCH. ASSUMING A STORM TRACK AS
CURRENTLY FORECAST, ACCUMULATIONS MAY EXCEED A FOOT OF SNOW OVER A
MODEST AREA. HOWEVER, DETERMINING THE RAIN/SNOW LINE COUPLED WITH
WHEN THE PRECIPITATION OCCURS (OVERNIGHT VS DAYTIME) WILL MAKE
SNOWFALL FORECASTS MORE DIFFICULT EVEN IN THE SHORT RANGE.
THE PAC NW WILL SEE PERIODS OF VALLEY RAIN AND HIGH ELEVATION SNOW
THAT SHOULD EXTEND EASTWARD INTO THE BITTERROOTS AND SAWTOOTH
RANGE AND TO YELLOWSTONE. SNOW LEVELS SHOULD REMAIN RATHER HIGH
GIVEN THE WARM PACIFIC AIR MASS MOVING IN. DOWNSTREAM
PRECIPITATION IN THE CENTRAL AND SOUTHERN PLAINS AND TN VALLEY IS
LESS CERTAIN, BUT AT LEAST SOME RAIN SHOULD BREAK OUT AHEAD OF THE
NEXT NORTHERN STREAM SYSTEM.
FRACASSO/KREKELER
(Day 3 PMDEPD: Valid 03/14/2017 to 03/18/2017)
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1056 AM EST SAT MAR 11 2017
VALID 12Z TUE MAR 14 2017 - 12Z SAT MAR 18 2017
...POWERFUL NOR'EASTER TO AFFECT THE MID-ATLANTIC AND NORTHEAST...
...OVERVIEW...
WITHIN AN AMPLIFIED ERN PAC TROUGH/WRN U.S. RIDGE/ERN TROUGH MEAN
PATTERN ALOFT, A LATE-WINTER STORM THAT WILL LIKELY SPREAD HEAVY
PRECIP ACROSS THE MID ATLC/NORTHEAST IN THE EARLY-MID WEEK TIME
FRAME WILL BE A DOMINANT FEATURE OF THE FCST. EXPECT MOSTLY SNOW
TO THE W OF THE I-95 CORRIDOR WITH RAIN OR A MIX CLOSER TO THE
COAST. EJECTING ERN PAC ENERGY HEADING INTO/AROUND THE MEAN RIDGE
MAY SUPPORT A SFC LOW/FRONTAL SYSTEM REACHING THE EAST TOWARD DAY
7 SAT WITH A FAIR AMOUNT OF UNCERTAINTY IN EVOLUTION. THE OVERALL
PATTERN AND THE EAST COAST STORM IN PARTICULAR WILL SUPPORT
UNSEASONABLY COLD TEMPS OVER THE EAST WHILE THE SOUTHWEST/GREAT
BASIN AND CENTRAL/SOUTHERN ROCKIES SHOULD SEE JUST THE OPPOSITE --
VERY WARM TEMPERATURES THAT MAY CHALLENGE SOME DAILY RECORDS.
...GUIDANCE PREFERENCES AND EVALUATION...
REGARDING THE STORM AFFECTING THE MID ATLC/NORTHEAST, OVER THE
PAST DAY THE MODEL AND ENSEMBLE GUIDANCE HAS TIGHTENED ITS
CLUSTERING FOR SFC LOW TRACK CONSIDERABLY. RECENT PREFS BTWN MORE
WRN GFS RUNS AND OFFSHORE ECMWF RUNS HAVE HELD UP WELL AS THE
CENTER OF 00Z ENSEMBLE CLUSTERING LIES BTWN THE TWO CAMPS FROM
YDAY. AS OF 12Z DAY 4 WED THE SFC LOW IS FCST TO BE A FRACTION
OFF THE COAST OF SRN MAINE. AN AVG OF THE 06Z GFS AND 00Z
ECMWF/UKMET/CMC REPRESENT CONSENSUS EVOLUTION WELL. THERE ARE
STILL LINGERING UNCERTAINTIES ALOFT THAT MAY TAKE WELL INTO THE
SHORT RANGE TIME FRAME TO RESOLVE SATISFACTORILY. THESE
UNCERTAINTIES FOCUS ON THE INTERACTION BTWN LEADING SHRTWV ENERGY,
NOW NEARING THE PAC NW AND FCST TO REACH THE EAST COAST EARLY TUE,
AND INITIALLY SHEARED SRN CANADA ENERGY LIKELY TO EVOLVE INTO A
GRTLKS/NORTHEAST CLOSED LOW. THE GENERAL THEME OF LATEST GUIDANCE
IS THAT THE LEADING PIECE OF ENERGY MAY SETTLE OVER NEW ENGLAND AS
THE GRTLKS ENERGY APPROACHES/PSBLY MERGES WITH IT, LEADING TO A
24-36 HOUR PERIOD WHEN THE SYSTEM MAY EITHER STALL OR IN SOME
FASHION REDEVELOP NEAR NEW ENGLAND. SUCH AN EVOLUTION WOULD RAISE
THE POTENTIAL FOR SOME LOCALLY VERY HIGH SNOW ACCUMULATIONS. THE
STRONG WINDS ACCOMPANYING THIS STORM WILL BE ANOTHER IMPORTANT
ELEMENT TO MONITOR.
THE OPERATIONAL MODEL CONSENSUS FAVORED EARLY IN THE PERIOD FOR
THE EAST COAST STORM REPRESENTS THE MAJORITY OF GUIDANCE WELL OVER
THE ERN PAC AS WELL. IN PARTICULAR THE 00Z ECMWF IS A WEAK
EXTREME WITH A SYSTEM TRACKING CLOSE TO HAIDA GWAII BY EARLY WED.
THERE IS REASONABLE AGREEMENT FOR THE TRAILING FRONT THOUGH. THE
SUPPORTING SHRTWV ENERGY WILL PASS THROUGH THE WRN RIDGE AROUND
DAY 5 THU, AFTER WHICH TIME GUIDANCE DIVERGES AS THE ENERGY
AMPLIFIES INTO THE ERN U.S. MEAN TROUGH. THUS FAR OPERATIONAL
MODEL RUNS AND ENSEMBLE MEMBERS HAVE NOT AGREED WELL ON WHERE THE
STRONGEST CONCENTRATION OF MID LVL ENERGY/ASSOC SFC REFLECTION
WILL BE BY FRI-SAT. PIECING TOGETHER THE VARIED SOLNS YIELDS A
MOST LIKELY SCENARIO OF A SYSTEM TRACKING NEAR THE UPR GRTLKS,
THOUGH STRENGTHENING/SHARPENING OF THE UPSTREAM RIDGE COULD ALLOW
FOR MORE TROUGH AMPLIFICATION AND A LITTLE FARTHER SWD TRACK
PARTIALLY TOWARD THE 06Z GEFS MEAN. 00Z ECMWF/CMC RUNS HAVE THEIR
BEST DEFINED LOWS WELL NWWD BY SAT BUT OTHERWISE THEIR PATTERN
COMPARES BETTER TO THE MEANS THAN THE GFS RUNS/ESPECIALLY THE 06Z
VERSION. SLOWER TREND VS CONTINUITY IS PLAUSIBLE GIVEN THE
AMPLITUDE OF THE PATTERN.
THE LAST SYSTEM OF INTEREST IS A FRONT FCST TO REACH NEAR THE PAC
NW COAST BY DAY 7 SAT. TIMING DIFFS ARE FAIRLY MODEST FOR A FCST
THAT FAR OUT IN TIME. ACCOUNTING FOR PREFS IN THE LATTER PART OF
THE PERIOD, THE OPERATIONAL MODEL FOCUSED BLEND TUE-THU ADJUSTS TO
INCORPORATING IDEAS FROM THE 00Z ECMWF/CMC AND 06Z GEFS MEAN/00Z
ECMWF MEAN/WPC CONTINUITY.
...WEATHER HIGHLIGHTS...
THE EARLY PERIOD STORM NEAR THE EAST COAST WILL BRING AREAS OF
HEAVY SNOW AND LIKELY COASTAL RAIN/MIX ALONG WITH STRONG WINDS TO
THE NRN MID ATLC/NORTHEAST THROUGH MIDWEEK. POTENTIAL FOR THE
STORM TO EXPERIENCE A PERIOD OF SLOW MOVEMENT MAY ALLOW FOR
FURTHER ENHANCEMENT OF ACCUMULATIONS AT SOME LOCATIONS. PRECIP
SHOULD SLOWLY EXIT BY LATE THU INTO FRI AS WRAP-AROUND SNOW
SHOWERS TAPER OFF IN NORTHERN NEW ENGLAND. TRAILING HIGH PRESSURE
MOVING SOUTHEASTWARD FROM NORTH OF MINNESOTA INTO THE SOUTHEAST
WILL HELP RADIATE OVER (PRESUMABLY) SNOW-COVERED AREAS WHICH COULD
BRING MIN TEMPERATURES TO WITHIN A FEW DEGREES OF RECORD LOWS
GIVEN CLEAR SKIES AND LIGHT WINDS. AT THE LEAST, IT WILL BE
UNSEASONABLY COLD FOR MID-MARCH AND POTENTIALLY HARMFUL TO SOME
FLOWERS THAT WERE LURED OUT BY THE WARM FEBRUARY. IN TERMS OF
ANOMALIES THERE SHOULD BE BROAD COVERAGE OF 10-20F BELOW NORMAL
READINGS WITH SOME AREAS 20-30F BELOW NORMAL ONE OR MORE DAYS
EARLY IN THE PERIOD. TEMPS SHOULD MODERATE BY FRI-SAT.
THE PAC NW WILL SEE PERIODS OF VALLEY RAIN AND HIGHER ELEVATION
SNOW THAT SHOULD EXTEND EASTWARD INTO THE BITTERROOTS AND SAWTOOTH
RANGE AND TO YELLOWSTONE AS THE FRONT COMING ASHORE AROUND WED
MOVES EASTWARD. SNOW LEVELS SHOULD REMAIN RATHER HIGH GIVEN THE
WARM PACIFIC AIR MASS MOVING IN. COVERAGE/INTENSITY/TYPE OF
DOWNSTREAM PRECIPITATION FROM THE PLAINS INTO THE EAST LATE WEEK
INTO THE WEEKEND IS LESS CERTAIN, WITH SNOW NORTH AND RAIN SOUTH.
TELECONNECTIONS RELATIVE TO THE MEAN PATTERN AS WELL AS NRN STREAM
DOMINANCE OF THE DYNAMIC SUPPORT AND A FAIRLY WEAK SIGNAL FOR ANY
SIGNIFICANT LOW LEVEL GULF INFLOW SEEM TO FAVOR LEANING AWAY FROM
THE HEAVIER SIDE OF THE SPREAD AT LEAST ACROSS THE SOUTH. NEXT
SYSTEM TO AFFECT THE NORTHWEST SHOULD BRING IN ANOTHER PERIOD OF
ENHANCED MOISTURE AROUND FRI-SAT.
IN CONTRAST TO THE WINTRY WEATHER OVER THE EAST, EXPECT A
PROLONGED PERIOD OF VERY WARM TEMPS OVER THE WEST AND AT TIMES
EXTENDING INTO THE PLAINS. CURRENT FCST HAS MIN/MAX VALUES
AVERAGING 10-20F ABOVE NORMAL DURING THE FULL 5-DAY PERIOD FOR A
CONSIDERABLE PORTION OF THIS AREA, WITH EACH DAY PROVIDING THE
POTENTIAL FOR SOME DAILY RECORD HIGHS AND/OR WARM LOWS.
RAUSCH/FRACASSO
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