NWS Climate Prediction Center



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Latest 6 to 10 Day Temperature Outlook

Prognostic Discussions


Valid: May 16 - 20, 2021 (6-10 Day Outlook)
Valid: May 18 - 24, 2021 (8-14 Day Outlook)
Issued: May 10, 2021


Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks 
NWS Climate Prediction Center College Park, MD 
300 PM EDT Mon May 10 2021 
 
6-10 DAY OUTLOOK FOR MAY 16 - 20 2021 
 
The GEFS, ECMWF, and Canadian dynamical models are in good agreement with  
regard to the 6-10 day 500-hPa geopotential height pattern over North America.  
Troughing and associated negative 500-hPa height anomalies are predicted over  
the Bering Sea and eastward across western Alaska. Across the western CONUS,  
increased mid-level troughing is predicted, compared to yesterday's 6-10 day  
forecast, while in the eastern CONUS, ridging is forecast with positive 500-hPa  
height anomalies. 
 
Increased probabilities for below normal temperatures are highlighted across  
parts of the Southeast, consistent with the consolidation forecast tool.  Above  
normal temperatures are favored over the Northeast and central CONUS, extending  
westward to the Rockies and parts of the Great Basin, underneath near to above  
normal mid-level heights and low level southerly flow. Near to below normal  
temperatures are forecast over the West Coast and Alaska Panhandle due to  
predicted low level northerly flow over the region.  
Near to above normal temperatures are favored across much of Mainland Alaska  
and the Aleutians, due to forecast enhanced southerly surface and mid-level  
flow ahead of a mean trough over the Bering Sea. 
 
Below normal precipitation is favored over most of the eastern CONUS,  
underneath above normal 500-hPa heights. Southerly flow and frontal activities  
increase odds of above normal precipitation over the Mississippi Valley, Great  
Plains, and the western Great Lakes. Below normal precipitation is favored for  
the Southern High Plains, the southern Rockies, and parts of the northwestern  
CONUS, consistent with the consolidation forecast tool. Over central and  
southern Alaska, an active storm track is favored on the northern periphery of  
the mean Pacific ridge, leading to increased odds of above normal precipitation. 
 
The official 6-10 day 500-hPa height blend consists of 15% of Today's 6z GFS  
Ensemble Mean centered on Day 8, 15% of Today's GFS Superensemble Mean centered  
on Day 8, 10% of Today's operational 6z GFS centered on Day 8, 30% of Today's  
0z European Ensemble Mean centered on Day 8, 10% of Today's operational 0z  
ECMWF centered on Day 8, and 20% of Today's 0z Canadian Ensemble Mean centered  
on Day 8  
  
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Average, 4 out of 5, due to decent  
agreement in the model mid-level height forecasts, offset by differences among  
the forecast tools in the predicted temperature and precipitation fields. 
 
8-14 DAY OUTLOOK FOR MAY 18 - 24 2021  
 
The predicted 500-hPa height pattern during the Week-2 period depicts mean  
mid-level troughing and weak negative height anomalies across the western  
CONUS. Positive height anomalies are predicted elsewhere over the CONUS, underneath mean ridging and anticyclonic mid-level flow. Over Alaska, negative 500-hPa height anomalies are predicted for much of the Mainland and Aleutians, associated with mean troughing over the Bering Sea and western Alaska. Below normal temperature probabilities are increased across parts of the West Coast and Alaska Panhandle, with increased troughing over the region. Near to below normal temperatures are predicted over parts of the Southeast, consistent with the consolidation forecast tool. As high pressure shifts eastward across the eastern CONUS throughout the period, return flow from the Gulf of Mexico on its western periphery favors increased probabilities of above normal temperatures for the remainder of the CONUS. Mean southerly to southwesterly flow favors above normal temperatures across much of the Alaska mainland and the Aleutians. Odds tilt toward below normal precipitation for much of the East Coast, associated with mean surface high pressure. Increased odds of above normal precipitation in the Central CONUS are associated with southerly flow and moisture advection from the Gulf of Mexico behind surface high pressure in the Southeast and ahead of a mean mid-level trough over the West. Despite the mean trough over the Western CONUS, energy crossing the northwestern CONUS and southern Rockies is not favored to amplify until it reaches the Plains, leading to enhanced below normal precipitation probabilities in the northwestern CONUS and Four Corners and Southern High Rockies. Above normal precipitation chances continue to be increased over Alaska due to troughing over the Bering Sea and the west coast of Mainland Alaska and the ridging over the eastern Pacific, favoring an active storm track across much of Alaska. The official 8-14 day 500-hPa height blend consists of: 15% of Today's 6z GFS Ensemble Mean centered on Day 11, 15% of Today's GFS Superensemble Mean centered on Day 11, 10% of Today's operational 6z GFS centered on Day 11, 40% of Today's 0z European Ensemble Mean centered on Day 11, and 20% of Today's 0z Canadian Ensemble Mean centered on Day 11 FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Average, 3 out of 5, due to good day-to-day consistency in the ECMWF and Canadian ensemble model guidance, offset by continued uncertainty in GEFS and the temperature fields over the CONUS and Alaska. FORECASTER: Y. Fan 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 May 20. 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: 20080520 - 19710424 - 20080507 - 19800508 - 19950521 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: 20080520 - 19990419 - 20080506 - 19710425 - 19780502 6-10 DAY OUTLOOK TABLE Outlook for May 16 - 20 2021 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B B OREGON N B NRN CALIF N B SRN CALIF B N IDAHO A N NEVADA N N W MONTANA A N E MONTANA A A WYOMING A A UTAH A N ARIZONA N N COLORADO A N NEW MEXICO A B N DAKOTA A A S DAKOTA A A NEBRASKA A A KANSAS A A OKLAHOMA A A N TEXAS A A S TEXAS A A W TEXAS A N MINNESOTA A A IOWA A A MISSOURI A A ARKANSAS A A LOUISIANA N A WISCONSIN A A ILLINOIS A A MISSISSIPPI N N MICHIGAN A A INDIANA A N OHIO A B KENTUCKY A B TENNESSEE N B ALABAMA N B NEW YORK A B VERMONT A B NEW HAMP A B MAINE A B MASS A B CONN A B RHODE IS A B PENN A B NEW JERSEY A B W VIRGINIA A B MARYLAND A B DELAWARE A B VIRGINIA N B N CAROLINA N B S CAROLINA B B GEORGIA B B FL PNHDL B B FL PENIN B B AK N SLOPE A N AK ALEUTIAN A A AK WESTERN A A AK INT BSN A A AK S INT N A AK SO COAST N A AK PNHDL B A 8-14 DAY OUTLOOK TABLE Outlook for May 18 - 24 2021 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON N B OREGON N B NRN CALIF N B SRN CALIF N N IDAHO A N NEVADA A B W MONTANA A N E MONTANA A N WYOMING A N UTAH A B ARIZONA N N COLORADO A B NEW MEXICO A B N DAKOTA A A S DAKOTA A A NEBRASKA A A KANSAS A A OKLAHOMA A A N TEXAS A A S TEXAS A A W TEXAS A N MINNESOTA A A IOWA A A MISSOURI A A ARKANSAS A A LOUISIANA A A WISCONSIN A A ILLINOIS A A MISSISSIPPI A A MICHIGAN A A INDIANA A A OHIO A N KENTUCKY A N TENNESSEE A B ALABAMA A B NEW YORK A B VERMONT A B NEW HAMP A B MAINE A B MASS A B CONN A B RHODE IS A B PENN A B NEW JERSEY A B W VIRGINIA A B MARYLAND A B DELAWARE A B VIRGINIA A B N CAROLINA N B S CAROLINA N B GEORGIA N B FL PNHDL N B FL PENIN N B AK N SLOPE A N AK ALEUTIAN A A AK WESTERN A A AK INT BSN A A AK S INT N A AK SO COAST N A AK PNHDL B 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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