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FXUS06 KWBC 211935
PMDMRD
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT THU SEPTEMBER 21 2017

6-10 DAY OUTLOOK FOR SEP 27 - OCT 01, 2017

TODAY`S ENSEMBLE MEAN SOLUTIONS ARE IN RELATIVELY GOOD AGREEMENT ON A FAIRLY
AMPLIFIED FLOW PATTERN OVER MUCH OF THE FORECAST DOMAIN. HOWEVER, SPREAD AND
UNCERTAINTY ARE HIGH AMONG THE COMPONENT ENSEMBLE MEMBERS OVER MUCH OF THE
COUNTRY, ESPECIALLY IN THE WESTERN CONUS. A TROUGH IS FORECAST OVER
SOUTHWESTERN MAINLAND ALASKA AND A RIDGE IS EXPECTED TO BUILD DOWNSTREAM OVER
THE NORTHWESTERN CONUS. TROUGHS ARE PREDICTED OVER THE SOUTHWESTERN CONUS AND
THE UPPER MISSISSIPPI VALLEY. ENSEMBLE SPREAD IS HIGHEST NEAR THE EAST COAST OF
THE CONUS IN ASSOCIATION WITH THE PREDICTED PATH OF HURRICANE MARIA, AND IN THE
WESTERN CONUS ASSOCIATED WITH UNCERTAINTY ABOUT THE EXACT POSITION AND
AMPLITUDE OF THE RIDGE/TROUGH PATTERN FORECAST THERE. TODAY`S NHC GUIDANCE
DEPICTS HURRICANE MARIA TO CURVE NORTH AND NORTHEAST, WITH NO EXPECTED MAJOR
IMPACTS TO THE U.S. AT THIS TIME. BECAUSE THERE IS STILL PLENTY OF UNCERTAINTY
IN THE TRACK, INTERESTS ALONG THE EAST COAST ARE STRONGLY ENCOURAGED TO CLOSELY
MONITOR THE LATEST UPDATES FROM THE NHC FOR TRACK AND INTENSITY GUIDANCE AND
POTENTIAL IMPACTS. TODAY`S MANUAL 500-HPA HEIGHT BLEND IS WEIGHTED MOST HEAVILY
TOWARD THE 0Z ECMWF ENSEMBLE MEAN SOLUTION BASED PRIMARILY ON CONSIDERATIONS OF
RECENT SKILL.

A TROUGH OVER THE SOUTHWESTERN CONUS TILTS THE ODDS TO BELOW NORMAL
TEMPERATURES FOR MUCH OF THE WEST-CENTRAL CONUS. ABOVE NORMAL TEMPERATURES ARE
FAVORED ALONG THE WEST COAST DUE TO A BUILDING RIDGE AND ABOVE NORMAL SSTS.
ENHANCED PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE INDICATED FOR THE
EASTERN CONUS AND PARTS OF THE GULF COAST DUE TO LARGE POSITIVE TEMPERATURE
ANOMALIES FORECAST IN THE BEGINNING OF THE PERIOD. ABOVE NORMAL TEMPERATURES
ARE FAVORED FOR PARTS OF EASTERN AND CENTRAL MAINLAND ALASKA, AND THE
PANHANDLE, CONSISTENT WITH OUR REFORECAST-CALIBRATED CONSOLIDATED FORECAST
GUIDANCE. ENHANCED PROBABILITIES FOR BELOW NORMAL TEMPERATURES ARE INDICATED
FOR PARTS OF THE ALEUTIANS DUE TO ANOMALOUS NORTHERLY FLOW.

THERE ARE ENHANCED PROBABILITIES FOR ABOVE NORMAL PRECIPITATION OVER MUCH OF
THE SOUTH-CENTRAL CONUS AND PARTS OF THE SOUTHWEST IN ASSOCIATION WITH A TROUGH
OVER THE SOUTHWESTERN CONUS, AND THE POTENTIAL ADVECTION OF TROPICAL MOISTURE
INTO THE REGION. BELOW NORMAL PRECIPITATION IS FAVORED FOR THE NORTHWESTERN
CONUS DUE TO EXPECTED RIDGING. THERE ARE INCREASED ODDS FOR ABOVE NORMAL
PRECIPITATION FOR PARTS OF THE NORTHEAST DUE TO A STORM SYSTEM PREDICTED TO
DEVELOP NEAR THE END OF THE PERIOD, AS WELL AS POSSIBLE EFFECTS OF HURRICANE
MARIA. HOWEVER TODAY`S NHC GUIDANCE FAVORS THE HURRICANE RECURVING AND NOT
IMPACTING THE U.S. NEVERTHELESS UNCERTAINTY IS HIGH WITH THIS STORM, AND
INTERESTS ALONG THE EAST COAST ARE STRONGLY ENCOURAGED TO CLOSELY MONITOR THE
LATEST UPDATES FROM THE NHC. THE TROUGH OVER ALASKA LEADS TO INCREASED ODDS FOR
ABOVE NORMAL PRECIPITATION FOR EASTERN MAINLAND ALASKA AND THE ALASKA
PANHANDLE. BELOW NORMAL PRECIPITATION IS FAVORED WEST OF THE TROUGH FOR PARTS
OF WESTERN MAINLAND ALASKA AND THE ALEUTIANS. BELOW NORMAL PRECIPITATION IS
FAVORED FOR MUCH OF THE SOUTHEASTERN CONUS IN ASSOCIATION WITH SUBTROPICAL
RIDGING OVER THE WESTERN GULF OF MEXICO AND CONSISTENT WITH CALIBRATED
PRECIPITATION GUIDANCE FROM THE ECMWF AND GFS ENSEMBLES.

TODAY`S OFFICIAL 500-HPA BLEND CONSISTS OF 20% OF TODAY`S OPERATIONAL 6Z GFS
CENTERED ON DAY 8, 50% OF TODAY`S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8,
AND 30% OF TODAY`S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8


FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO
GOOD AGREEMENT AMONG THE MODELS AND TOOLS OVER MOST OF THE U.S., AND LESS
UNCERTAINTY IN THE TRACK OF HURRICANE MARIA THAN YESTERDAY

8-14 DAY OUTLOOK FOR SEP 29 - OCT 05, 2017

DURING THE WEEK-2 PERIOD, THE OVERALL 500-HPA FLOW PATTERN IS EXPECTED TO BE
VERY SIMILAR, EXCEPT SOMEWHAT LESS AMPLIFIED.

THE TEMPERATURE PROBABILITIES FORECAST DURING THE 6-10 DAY PERIOD ARE SIMILAR
TO THOSE FORECAST DURING THE WEEK-2 PERIOD, WITH A FEW EXCEPTIONS. LESS
NORTHERLY LOW-LEVEL FLOW IS FORECAST OVER ALASKA DURING THE WEEK-2 PERIOD,
FAVORING ABOVE NORMAL TEMPERATURES FOR MOST OF THE STATE. DURING THE 6-10 DAY
PERIOD, DESPITE A TROUGH PASSING THROUGH PARTS OF THE EASTERN U.S., LARGE
POSITIVE TEMPERATURE ANOMALIES DURING THE BEGINNING OF THE PERIOD RESULTED IN
ABOVE NORMAL TEMPERATURES FOR THE EAST. DURING THE WEEK-2 PERIOD, MUCH OF THE
EASTERN U.S. IS BEHIND THE FRONT DURING THE ENTIRE PERIOD, SO NEAR TO BELOW
NORMAL TEMPERATURES ARE FAVORED FOR PARTS OF THE EAST, EXCEPT FOR COASTAL
PORTIONS OF THE SOUTHEAST AND FLORIDA WHICH ARE FORECAST TO REMAIN AHEAD OF THE
FRONT.

THE PRECIPITATION PROBABILITIES FORECAST DURING THE 6-10 DAY PERIOD ARE SIMILAR
TO THE WEEK-2 PERIOD, WITH SOME EXCEPTIONS. AS SURFACE HIGH PRESSURE IS
FORECAST TO SPREAD EASTWARD INTO THE OHIO VALLEY BY THE WEEK-2 PERIOD, ENHANCED
PROBABILITIES FOR BELOW NORMAL PRECIPITATION ARE EXPECTED FOR MUCH OF THE
MISSISSIPPI AND OHIO VALLEYS. CHANCES FOR ABOVE NORMAL PRECIPITATION ARE
ELEVATED FOR PARTS OF FLORIDA AND THE MID-ATLANTIC REGION WHERE SEVERAL STORM
SYSTEMS ARE EXPECTED TO DEVELOP DURING THE PERIOD.

THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF: 20% OF TODAY`S 6Z GFS ENSEMBLE
MEAN CENTERED ON DAY 11, 30% OF TODAY`S OPERATIONAL 6Z GFS CENTERED ON DAY 11,
AND 50% OF TODAY`S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11


FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOVE AVERAGE, 4 OUT OF 5, DUE
TO GOOD AGREEMENT AMONG THE MODELS AND TOOLS OVER MOST OF THE U.S., AND LESS
UNCERTAINTY IN THE TRACK OF HURRICANE MARIA THAN YESTERDAY

FORECASTER: MIKE C

NOTES:


AUTOMATED FORECASTS ARE ISSUED ON SATURDAY AND SUNDAY. OCCASIONALLY MANUAL
INTERVENTION IS NECESSARY TO ADDRESS QUALITY CONTROL AND CONSISTENCY ISSUES.
IN THESE CASES, FORECASTS ARE MANUALLY DRAWN BUT A FULL DISCUSSION IS NOT
ISSUED.

THE NOTATION FOR THE CATEGORICAL FORECAST INDICATED ON THE MAPS IS
THE SAME AS THAT IN THE TABLES: A-ABOVE   N-NEAR NORMAL   B-BELOW

THE TEMPERATURE MAP SHOWS REGIONS WITH > 33% CHANCE OF BEING WARMER
(ORANGE, "A"), COLDER (BLUE, "B"), OR CLOSE TO (UNSHADED, "N")
HISTORICAL AVERAGE VALUES FOR THE CALENDAR PERIOD OF THE FORECAST
(DASHES, "F").  LABELS ON THE SHADED LINES GIVE THE PROBABILITY
(> 33%) OF THE MORE LIKELY CATEGORY (B OR A).  PROBABILITY OF N IS
ALWAYS < 40%.

THE PRECIPITATION MAP SHOWS REGIONS WITH > 33% CHANCE OF BEING
WETTER (GREEN, "A"), DRIER (TAN, "B"), OR CLOSE TO (UNSHADED, "N")
HISTORICAL MEDIAN VALUES FOR THE CALENDAR PERIOD OF THE FORECAST
(DASHES, "INCHES").  LABELS ON THE SHADED LINES GIVE THE PROBABILITY
(> 33%) OF THE MORE LIKELY CATEGORY (B OR A).  PROBABILITY OF N IS
ALWAYS < 40%.

IN THE SOUTHWEST AND OTHER CLIMATOLOGICALLY DRY REGIONS - THERE WILL
BE A GREATER THAN 33.3% CHANCE OF NO PRECIPITATION AND OCCASIONALLY
EVEN A NORMAL (I.E. MEDIAN) VALUE OF ZERO - ESPECIALLY DURING THE DRY
SEASONS.  IN SUCH CASES A FORECAST OF NEAR NORMAL IS EFFECTIVELY A
FORECAST OF LITTLE OR NO PRECIPITATION.

THE CLIMATE PREDICTION CENTER USES 1981-2010 BASE PERIOD MEANS FOR
TEMPERATURE...PRECIPITATION...AND 500-HPA HEIGHTS AS REFERENCE IN
THE CLIMATE OUTLOOKS.

THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON
OCTOBER 19

ANALOGS TO THE 5 DAY MEAN OBSERVED PATTERN CENTERED 3 DAYS AGO (D-3)
FOR THE REGION FROM 20N TO 70N LATITUDE AND 175E TO 60W LONGITUDE
INCLUDE THE 5 DAY PERIODS CENTERED ON THE FOLLOWING DATES:
19860924 - 20040917 - 19770922 - 19710927 - 19970914


ANALOGS TO THE 7 DAY MEAN OBSERVED PATTERN CENTERED 4 DAYS AGO (D-4)
FOR THE REGION FROM 20N TO 70N LATITUDE AND 175E TO 60W LONGITUDE
INCLUDE THE 7 DAY PERIODS CENTERED ON THE FOLLOWING DATES:
19860926 - 19970914 - 19710928 - 20040916 - 19770922


6-10 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 27 - OCT 01, 2017

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  A    B     OREGON      A    B     NRN CALIF   A    B
SRN CALIF   A    N     IDAHO       A    B     NEVADA      A    B
W MONTANA   A    B     E MONTANA   A    B     WYOMING     B    B
UTAH        N    B     ARIZONA     B    N     COLORADO    B    A
NEW MEXICO  B    A     N DAKOTA    N    B     S DAKOTA    N    B
NEBRASKA    N    B     KANSAS      B    A     OKLAHOMA    B    A
N TEXAS     B    A     S TEXAS     A    A     W TEXAS     B    A
MINNESOTA   N    B     IOWA        N    B     MISSOURI    N    B
ARKANSAS    A    A     LOUISIANA   A    A     WISCONSIN   N    B
ILLINOIS    N    B     MISSISSIPPI A    N     MICHIGAN    A    N
INDIANA     A    N     OHIO        A    N     KENTUCKY    A    N
TENNESSEE   A    B     ALABAMA     A    B     NEW YORK    A    N
VERMONT     A    A     NEW HAMP    A    A     MAINE       A    A
MASS        A    A     CONN        A    A     RHODE IS    A    A
PENN        A    N     NEW JERSEY  A    A     W VIRGINIA  A    N
MARYLAND    A    N     DELAWARE    A    A     VIRGINIA    A    N
N CAROLINA  A    N     S CAROLINA  A    B     GEORGIA     A    B
FL PNHDL    A    B     FL PENIN    A    B     AK N SLOPE  N    N
AK ALEUTIAN B    B     AK WESTERN  N    B     AK INT BSN  N    B
AK S INT    A    B     AK SO COAST A    B     AK PNHDL    A    N



8-14 DAY OUTLOOK TABLE
OUTLOOK FOR SEP 29 - OCT 05, 2017

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  A    B     OREGON      A    B     NRN CALIF   A    B
SRN CALIF   A    N     IDAHO       A    B     NEVADA      A    B
W MONTANA   A    B     E MONTANA   A    B     WYOMING     N    B
UTAH        A    B     ARIZONA     A    N     COLORADO    N    A
NEW MEXICO  B    A     N DAKOTA    N    B     S DAKOTA    N    B
NEBRASKA    B    B     KANSAS      B    B     OKLAHOMA    B    B
N TEXAS     B    A     S TEXAS     B    A     W TEXAS     B    A
MINNESOTA   N    B     IOWA        B    B     MISSOURI    B    B
ARKANSAS    B    B     LOUISIANA   B    N     WISCONSIN   B    B
ILLINOIS    B    B     MISSISSIPPI B    N     MICHIGAN    B    B
INDIANA     B    B     OHIO        B    B     KENTUCKY    B    B
TENNESSEE   B    B     ALABAMA     N    N     NEW YORK    B    N
VERMONT     N    N     NEW HAMP    N    N     MAINE       N    N
MASS        N    N     CONN        N    N     RHODE IS    N    N
PENN        B    N     NEW JERSEY  N    N     W VIRGINIA  B    N
MARYLAND    B    A     DELAWARE    N    A     VIRGINIA    B    A
N CAROLINA  N    A     S CAROLINA  A    A     GEORGIA     A    N
FL PNHDL    A    N     FL PENIN    A    A     AK N SLOPE  A    N
AK ALEUTIAN N    B     AK WESTERN  A    B     AK INT BSN  A    B
AK S INT    A    B     AK SO COAST A    B     AK PNHDL    A    B

                           LEGEND
TEMPS WITH RESPECT TO NORMAL     PCPN WITH RESPECT TO MEDIAN
A - ABOVE   N  - NEAR NORMAL     A - ABOVE   N - NEAR MEDIAN
B - BELOW                        B - BELOW

THE FORECAST CLASSES REPRESENT AVERAGES FOR EACH STATE. NORMAL
VALUES - WHICH MAY VARY WIDELY ACROSS SOME STATES - ARE
AVAILABLE FROM YOUR LOCAL WEATHER SERVICE FORECAST OFFICE.

FOR ADDITIONAL INFORMATION SEE MESSAGE FXUS06 KWBC - ON AWIPS AS
PMDMRD.

$$




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