NWS Climate Prediction Center



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Latest 6 to 10 Day Temperature Outlook

Prognostic Discussions


Valid: Sep 28 - Oct 02, 2020 (6-10 Day Outlook)
Valid: Sep 30 - Oct 06, 2020 (8-14 Day Outlook)
Issued: Sep 22, 2020


Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks 
NWS Climate Prediction Center College Park, MD 
300 PM EDT Tue September 22 2020 
 
6-10 DAY OUTLOOK FOR SEP 28 - OCT 02, 2020 
 
Today's models show good agreement predicting an amplified circulation pattern  
across the forecast domain. An amplified trough is forecast over the North  
Pacific, with below normal 500-hPa geopotential heights to extend over the  
eastern Aleutians. A ridge is expected over parts of eastern Alaska, western  
Canada, and the western CONUS, favoring positive 500-hPa height anomalies over  
Mainland Alaska, the Alaska Panhandle, and much of the western CONUS. Over the  
last two days, models continue to predict an amplified trough over the central  
and eastern CONUS, leading to negative 500-hPa height anomalies over much of  
the eastern CONUS. Positive 500-hPa height anomalies over northern New England,  
associated with a predicted ridge over the North Atlantic, are expected to only  
last through the start of the 6-10 day period as the trough progresses slowly  
eastward. 
 
Near normal temperatures are favored for southwestern Mainland Alaska and the  
Aleutians underneath predicted near to slightly below normal 500-hPa heights.  
Above normal temperatures are favored for most of Mainland Alaska and the  
Alaska Panhandle, under positive 500-hPa height anomalies and anomalous  
southerly flow. Enhanced probabilities of above normal temperatures are  
predicted for the western half of the CONUS, under a  ridge and positive  
500-hPa height anomalies. Below normal temperatures are likely across much of  
the eastern half of the CONUS, in association with the trough over the central  
and eastern CONUS. Above normal temperatures are favored for parts of the  
Northeast, where positive 500-hPa height anomalies are expected early in the  
period, and over the southern Florida Peninsula, supported by both the ECMWF  
and GEFS model forecasts. 
 
In association with the predicted trough over the North Pacific, above normal  
precipitation is favored for central and eastern areas along the south coast of  
Alaska, southeastern Mainland Alaska, and the northern Alaska Panhandle. Below  
normal precipitation is favored over western areas of Mainland Alaska and parts  
of the Aleutians, to the west of the mean trough axis. Enhanced probabilities  
of below normal precipitation are predicted for much of the western and Central  
CONUS into the Southeast Region, under and ahead of an amplified ridge. Above  
normal precipitation is likely from the Great Lakes region southward into the  
Ohio Valley and eastward into the Mid-Atlantic and Northeast, ahead of the  
trough. The greatest probabilities for above normal precipitation exceed 50 percent for parts of the Northeast. The official 6-10 day 500-hPa height blend consists of 40% of Today's 6z GFS Ensemble Mean centered on Day 8, and 60% of Today's 0z European Ensemble Mean centered on Day 8 FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Above average, 4 out of 5, due to good agreement among the model 500-hPa circulation forecasts on an amplified flow pattern, offset by some differences among forecast tools for temperature and precipitation. 8-14 DAY OUTLOOK FOR SEP 30 - OCT 06, 2020 For the week-2 period, the 500-hPa circulation pattern forecast is similar to the 6-10 day period forecast with some slight eastward progression and deamplification, predicting a trough over the North Pacific, a ridge over eastern Alaska and the western CONUS, and a trough over the eastern CONUS. All ensemble means indicate some deamplification of the circulation pattern relative to the 6-10 day period forecast, with the ECMWF ensemble mean showing weaker 500-hPa height anomalies overall compared to the GEFS ensemble mean. Troughing over the eastern CONUS in particular is lower in amplitude in the ECMWF ensemble mean than that in the GEFS. Anomalous southerly flow and above normal 500-hPa heights lead to enhanced probabilities for above normal temperatures over Mainland Alaska and the Alaska Panhandle. Near normal temperatures are favored for the western Aleutians, under rising midlevel heights. The predicted ridge over the western CONUS increases chances of above normal temperatures across the western half of the
CONUS. Enhanced probabilities of below normal temperatures are predicted across most of the eastern CONUS, under the amplified trough, with probabilities exceeding 70 percent over parts of the Southeast. Above normal temperatures continue to be likely for parts of northern New England, under anomalous southerly flow and positive 500-hPa height anomalies early in the period. Probabilities for above normal precipitation continue to be elevated in week 2, for eastern Mainland Alaska and the Alaska Panhandle, ahead of the trough, along with continued below normal precipitation over parts of western Alaska. Elevated probabilities for below normal precipitation are predicted for almost the entire western, central, and southeastern CONUS under the ridge, outside of climatologically dry regions of the Southwest where near normal precipitation is favored. As the trough begins to deamplify and progress eastward, above normal precipitation continues to be likely for a smaller area of the Northeast. The official 8-14 day 500-hPa height blend consists of: 40% of Today's 6z GFS Ensemble Mean centered on Day 11, and 60% of Today's 0z European Ensemble Mean centered on Day 11 FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Above average, 4 out of 5, due to good agreement among the model 500-hPa circulation forecasts on an amplified flow pattern, offset by some differences among forecast tools for temperature and precipitation. FORECASTER: D Collins 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 15. 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: 19630919 - 19620925 - 19820906 - 19920929 - 20041006 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: 19920928 - 19630920 - 19551005 - 19620925 - 20070902 6-10 DAY OUTLOOK TABLE Outlook for Sep 28 - Oct 02, 2020 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 B NEVADA A B W MONTANA A B E MONTANA A B WYOMING A B UTAH A B ARIZONA A B COLORADO A B NEW MEXICO A B N DAKOTA B B S DAKOTA B B NEBRASKA B B KANSAS B B OKLAHOMA B B N TEXAS B B S TEXAS B B W TEXAS A B MINNESOTA B B IOWA B B MISSOURI B B ARKANSAS B B LOUISIANA B B WISCONSIN B A ILLINOIS B B MISSISSIPPI B B MICHIGAN B A INDIANA B A OHIO B A KENTUCKY B A TENNESSEE B B ALABAMA B B NEW YORK N A VERMONT A A NEW HAMP A A MAINE A A MASS A A CONN A A RHODE IS A A PENN B A NEW JERSEY N A W VIRGINIA B A MARYLAND B A DELAWARE B A VIRGINIA B A N CAROLINA B A S CAROLINA B B GEORGIA B B FL PNHDL B B FL PENIN A B AK N SLOPE N B AK ALEUTIAN N B AK WESTERN A 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 Sep 30 - Oct 06, 2020 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 B NEVADA A N W MONTANA A B E MONTANA A B WYOMING A B UTAH A B ARIZONA A N COLORADO A B NEW MEXICO A B N DAKOTA B B S DAKOTA B B NEBRASKA B B KANSAS B B OKLAHOMA B B N TEXAS B B S TEXAS B B W TEXAS A B MINNESOTA B B IOWA B B MISSOURI B B ARKANSAS B B LOUISIANA B B WISCONSIN B B ILLINOIS B B MISSISSIPPI B B MICHIGAN B N INDIANA B B OHIO B N KENTUCKY B B TENNESSEE B B ALABAMA B B NEW YORK B A VERMONT B A NEW HAMP N A MAINE A A MASS N A CONN B N RHODE IS N N PENN B N NEW JERSEY B B W VIRGINIA B B MARYLAND B B DELAWARE B B VIRGINIA B B N CAROLINA B B S CAROLINA B B GEORGIA B B FL PNHDL B B FL PENIN B B AK N SLOPE A N AK ALEUTIAN N B AK WESTERN A N AK INT BSN A A AK S INT A A AK SO COAST A A 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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