PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EDT TUE AUGUST 22 2017
6-10 DAY OUTLOOK FOR AUG 28 - SEP 01, 2017
TODAY'S MODEL SOLUTIONS ARE IN FAIRLY GOOD AGREEMENT ON THE PREDICTED
MID-TROPOSPHERIC FLOW PATTERN FOR NORTH AMERICA. AN AMPLIFIED PATTERN FOR THIS
TIME OF YEAR IS PREDICTED WITH A RIDGE EXPECTED OVER THE WESTERN CONUS AND
TROUGHS ANTICIPATED OVER SOUTHWESTERN ALASKA AND OVER THE EAST-CENTRAL CONUS
FROM THE GREAT LAKES TO THE WESTERN GULF COAST REGION. SEVERAL MODEL SOLUTIONS
(INCLUDING THE DETERMINISTIC 0Z ECMWF AND 6Z GFS) ALSO BRING SURFACE LOW
PRESSURE ASSOCIATED WITH THE REMNANTS OF TROPICAL STORM HARVEY TOWARD THE
WESTERN GULF COAST REGION. ENSEMBLE SPREAD IS MODERATE OVER MUCH OF THE
FORECAST DOMAIN BUT HIGH OVER THE GREAT LEAKS AND MISSISSIPPI VALLEY. MOST
ENSEMBLE MEMBERS INDICATE BELOW NORMAL HEIGHTS FOR SOUTHWESTERN ALASKA AND MUCH
OF THE EASTERN CONUS AND ABOVE NORMAL HEIGHTS FOR THE WESTERN CONUS.
RIDGING AND ABOVE NORMAL HEIGHTS FAVOR ABOVE NORMAL TEMPERATURES FOR THE
WESTERN CONUS. A FRONTAL BOUNDARY ASSOCIATED WITH THE TROUGH OVER THE EASTERN
CONUS IS EXPECTED TO PROGRESS FAR TO THE SOUTH FOR THIS TIME OF THE YEAR,
LEADING TO ENHANCED PROBABILITIES FOR BELOW NORMAL TEMPERATURES FOR MUCH OF THE
EASTERN CONUS. FAVORED ABOVE NORMAL TEMPERATURES ARE RESTRICTED TO THE SOUTHERN
FLORIDA PENINSULA TO THE SOUTH OF THE EXPECTED FRONTAL BOUNDARY. THE TROUGH
FORECAST OVER ALASKA TILTS THE ODDS TO BELOW NORMAL TEMPERATURES NEAR THE
ALASKA PENINSULA AND EASTERN ALEUTIANS, WHILE ABOVE NORMAL TEMPERATURE
PROBABILITIES ARE ENHANCED FOR THE ALASKA PANHANDLE AND PARTS OF EASTERN AND
CENTRAL MAINLAND ALASKA AHEAD OF THE TROUGH AXIS.
ABOVE NORMAL PRECIPITATION IS FAVORED FOR THE THE GULF COAST REGION EXTENDING
NORTH TO THE OHIO VALLEY DUE TO THE TROUGH, ASSOCIATED FRONTAL BOUNDARY, AND
AND POTENTIAL INFLUXES OF TROPICAL MOISTURE. SURFACE HIGH PRESSURE TILTS THE
ODDS TO BELOW NORMAL PRECIPITATION FOR PARTS OF THE NORTHEAST. RIDGING LEADS TO
ENHANCED PROBABILITIES FOR BELOW NORMAL PRECIPITATION FOR MUCH OF THE
NORTHWESTERN AND NORTH-CENTRAL CONUS. PROBABILITIES FOR ABOVE NORMAL
PRECIPITATION ARE ENHANCED FOR PARTS OF THE SOUTHWESTERN CONUS DUE TO POTENTIAL
ADVECTION OF TROPICAL MOISTURE INTO THE REGION, PARTICULARLY LATER IN THE
PERIOD. THE TROUGH EXPECTED OVER ALASKA TILTS THE ODDS TO ABOVE NORMAL
PRECIPITATION FOR SOUTHERN AND EASTERN MAINLAND ALASKA AND THE ALASKA PANHANDLE
WHILE BELOW NORMAL PRECIPITATION IS FAVORED FOR PARTS OF NORTHWESTERN MAINLAND
ALASKA UNDERNEATH ANOMALOUS EASTERLY FLOW.
TODAY'S OFFICIAL 500-HPA BLEND CONSISTS OF 20% OF TODAY'S 0Z GFS ENSEMBLE MEAN
CENTERED ON DAY 8, 15% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED ON DAY 8, 5% OF
TODAY'S OPERATIONAL 0Z GFS CENTERED ON DAY 8, 30% OF TODAY'S 0Z EUROPEAN
ENSEMBLE MEAN CENTERED ON DAY 8, 5% OF YESTERDAY'S 12Z EUROPEAN ENSEMBLE MEAN
CENTERED ON DAY 7, 5% OF TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8, 15% OF
TODAY'S 0Z CANADIAN ENSEMBLE MEAN CENTERED ON DAY 8, AND 5% OF YESTERDAY'S 12Z
CANADIAN ENSEMBLE MEAN CENTERED ON DAY 7
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO
FAIRLY GOOD MODEL AGREEMENT ON AN AMPLIFIED FLOW PATTERN OVER MUCH OF THE
FORECAST DOMAIN.
8-14 DAY OUTLOOK FOR AUG 30 - SEP 05, 2017
DURING THE WEEK-2 PERIOD, A TROUGH IS ANTICIPATED TO REMAIN OVER THE EASTERN
ALEUTIANS AND A RIDGE IS EXPECTED DOWNSTREAM OVER WESTERN CANADA AND EASTERN
MAINLAND ALASKA. RIDGING CONTINUES OVER THE WESTERN CONUS AND HEIGHTS ARE
EXPECTED TO REMAIN ABOVE NORMAL. A TROUGH IS ANTICIPATED OVER THE EAST-CENTRAL
CONUS CENTERED FROM THE GREAT LAKES TO THE WESTERN GULF COAST. THE ENSEMBLE
SPAGHETTI CHARTS INDICATE MODERATE SPREAD ACROSS MUCH OF THE FORECAST DOMAIN.
TODAY'S 500-HPA BLEND CHART INDICATES NEAR TO ABOVE NORMAL HEIGHTS OVER THE
WESTERN CONUS AND EASTERN ALASKA, WHILE NEAR TO BELOW NORMAL HEIGHTS ARE
ANTICIPATED OVER MUCH OF THE EASTERN AND SOUTH-CENTRAL CONUS AND SOUTHWESTERN
ALASKA.
THE TROUGH OVER THE EAST-CENTRAL CONUS LEADS TO ENHANCED PROBABILITIES FOR NEAR
TO BELOW NORMAL TEMPERATURES FOR MOST OF THE EASTERN AND CENTRAL CONUS WITH
ENHANCED ABOVE NORMAL TEMPERATURE PROBABILITIES RESTRICTED TO PARTS OF THE
FLORIDA PENINSULA AND EASTERN NEW ENGLAND. RIDGING AND ABOVE NORMAL HEIGHTS
ELEVATE CHANCES FOR ABOVE NORMAL TEMPERATURES FOR THE WESTERN THIRD OF THE
CONUS. ABOVE NORMAL TEMPERATURES ARE ALSO FAVORED FOR PARTS OF EASTERN AND
CENTRAL MAINLAND ALASKA AND THE ALASKA PANHANDLE AHEAD OF THE TROUGH EXPECTED
NEAR THE EASTERN ALEUTIANS.
RIDGING LEADS TO ENHANCED PROBABILITIES FOR BELOW NORMAL PRECIPITATION FOR MUCH
OF THE NORTHWESTERN AND NORTH-CENTRAL CONUS. A MEAN TROUGH TILTS THE ODDS TO
ABOVE NORMAL PRECIPITATION FROM THE GULF COAST REGION TO THE NORTHEAST.
PROBABILITIES FOR ABOVE NORMAL PRECIPITATION ARE ENHANCED FOR PARTS OF THE
SOUTHWESTERN CONUS DUE TO POTENTIAL ADVECTION OF TROPICAL MOISTURE INTO THE
REGION. MOIST FLOW AHEAD OF A TROUGH NEAR THE EASTERN ALEUTIANS LEADS TO
ENHANCED PROBABILITIES FOR ABOVE NORMAL PRECIPITATION FOR SOUTHEASTERN MAINLAND
ALASKA AND THE ALASKA PANHANDLE. BELOW NORMAL PRECIPITATION IS FAVORED FOR
PARTS OF WESTERN MAINLAND ALASKA UNDERNEATH ANOMALOUS EASTERLY FLOW.
THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF: 20% OF TODAY'S 0Z GFS ENSEMBLE
MEAN CENTERED ON DAY 11, 25% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED ON DAY
11, 30% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, 5% OF
YESTERDAY'S 12Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10, 15% OF TODAY'S 0Z
CANADIAN ENSEMBLE MEAN CENTERED ON DAY 11, AND 5% OF YESTERDAY'S 12Z CANADIAN
ENSEMBLE MEAN CENTERED ON DAY 10
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOVE AVERAGE, 4 OUT OF 5, DUE
TO FAIRLY GOOD AGREEMENT AMONG THE ENSEMBLE MEANS.
FORECASTER: SCOTT H
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
SEPTEMBER 21
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:
19530812 - 19580905 - 19660902 - 19800903 - 19910802
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:
19530812 - 19580904 - 19800902 - 19910801 - 19660901
6-10 DAY OUTLOOK TABLE
OUTLOOK FOR AUG 28 - SEP 01, 2017
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A N
SRN CALIF A N IDAHO A N NEVADA A N
W MONTANA A B E MONTANA A B WYOMING A B
UTAH A N ARIZONA A N COLORADO N N
NEW MEXICO N N N DAKOTA N B S DAKOTA N B
NEBRASKA B B KANSAS B B OKLAHOMA B B
N TEXAS B N S TEXAS B A W TEXAS B N
MINNESOTA N B IOWA B B MISSOURI B B
ARKANSAS B A LOUISIANA B A WISCONSIN N B
ILLINOIS B N MISSISSIPPI B A MICHIGAN N N
INDIANA B A OHIO B A KENTUCKY B A
TENNESSEE B A ALABAMA B A NEW YORK B N
VERMONT B B NEW HAMP N B MAINE N B
MASS N B CONN B N RHODE IS N N
PENN B N NEW JERSEY B N W VIRGINIA B A
MARYLAND B N DELAWARE B N VIRGINIA B N
N CAROLINA B N S CAROLINA B N GEORGIA B A
FL PNHDL B A FL PENIN A A AK N SLOPE N N
AK ALEUTIAN N N AK WESTERN N B AK INT BSN A A
AK S INT A A AK SO COAST A A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
OUTLOOK FOR AUG 30 - SEP 05, 2017
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A B OREGON A B NRN CALIF A N
SRN CALIF A A IDAHO A B NEVADA A A
W MONTANA A B E MONTANA A B WYOMING A B
UTAH A N ARIZONA A A COLORADO N N
NEW MEXICO N N N DAKOTA N B S DAKOTA N B
NEBRASKA B B KANSAS B B OKLAHOMA B N
N TEXAS B N S TEXAS B A W TEXAS B N
MINNESOTA B B IOWA B B MISSOURI B N
ARKANSAS B A LOUISIANA B A WISCONSIN B B
ILLINOIS B N MISSISSIPPI B A MICHIGAN N A
INDIANA B A OHIO B A KENTUCKY B A
TENNESSEE B A ALABAMA B A NEW YORK N A
VERMONT N A NEW HAMP A A MAINE A A
MASS A A CONN N A RHODE IS A A
PENN B A NEW JERSEY N A W VIRGINIA B A
MARYLAND N A DELAWARE N N VIRGINIA B A
N CAROLINA N N S CAROLINA B A GEORGIA B A
FL PNHDL N A FL PENIN A A AK N SLOPE N N
AK ALEUTIAN N N AK WESTERN N N AK INT BSN A A
AK S INT A A AK SO COAST N A AK PNHDL A A
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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