NWS Climate Prediction Center



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Latest 6 to 10 Day Temperature Outlook

Prognostic Discussions


Valid: May 11 - 15, 2021 (6-10 Day Outlook)
Valid: May 13 - 19, 2021 (8-14 Day Outlook)
Issued: May 05, 2021


Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks 
NWS Climate Prediction Center College Park, MD 
300 PM EDT Wed May 05 2021 
 
6-10 DAY OUTLOOK FOR MAY 11 - 15 2021 
 
The GEFS, ECMWF, and Canadian dynamical models are in good agreement in regards  
to the 6-10 day 500-hPa geopotential height pattern. Troughing is predicted  
over northeastern North America. The mid-level flow is forecast to become more  
zonal across the western CONUS, with ridging predicted over the eastern  
Pacific, extending northward through much of Alaska. Today’s manual 500-hPa  
height blend depicts near to above normal heights across much of the western  
CONUS, with the highest positive height anomalies forecast along the Pacific  
Coast. Below normal heights are favored across portions of the Central Plains,  
Great Lakes, Ohio and Tennessee Valleys, mid-Atlantic, and Northeast,  
underneath the influence of the trough over eastern Canada. Near normal heights  
are forecast across remaining areas of the central CONUS through the Southeast.  
Above normal heights are depicted across much of Alaska, except over parts of  
the western Aleutians, where near to below normal heights are favored  
underneath troughing forecast over the Bering Sea. 
 
Increased probabilities for below normal temperatures are highlighted across  
much of the CONUS east of the Rockies as a cold front is forecast to move  
through prior to the forecast period. Probabilities for above normal  
temperatures are increased over parts of extreme south Texas and the Florida  
Peninsula, where mid-level flow is predicted to be more zonal, and supported by  
the GEFS and ECMWF reforecast tools. Near to above normal temperatures are  
favored over the western third of the CONUS, with the highest probabilities for  
above normal temperatures forecast across Northern and Central California and  
Nevada, due to increased influence from the East Pacific ridge. Near to above  
normal temperatures are favored across Alaska underneath increased ridging and  
enhanced southerly surface and mid-level flow ahead of troughing and associated  
surface low pressure predicted over the Bering Sea.  
  
Frontally focused precipitation is favored across parts of the south-central  
and southeastern CONUS where enhanced Gulf of Mexico moisture flow could  
further enhance rainfall chances. Ridging and positive height anomalies along  
the West Coast of the CONUS favor increased chances for below normal  
precipitation across portions of the West. Below normal precipitation  
probabilities are also elevated over parts of the Midwest, Great Lakes, and  
Northeast. These areas are forecast to be on the backside of the aforementioned  
cold front, more influenced by northwesterly mid-level flow and surface high  
pressure. Probabilities for near to above normal precipitation are increased  
over most of Alaska due to troughing predicted across the Bering Sea and an  
active storm track across the state. 
 
The official 6-10 day 500-hPa height blend consists of 30% of Today's 6z GFS  
Ensemble Mean centered on Day 8, 5% of Today's operational 6z GFS centered on  
Day 8, 40% of Today's 0z European Ensemble Mean centered on Day 8, 5% 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, 3 out of 5, due to good  
agreement in the model mid-level height forecast, offset by forecasts trending  
toward a low amplitude pattern. 
 
8-14 DAY OUTLOOK FOR MAY 13 - 19 2021  
 
The predicted 500-hPa height pattern during the week-2 period is similar to the  
6-10 day period, but less amplified. Although the mean mid-level flow across  
the CONUS is predicted to be predominately zonal, the ECMWF, GEFS, and Canadian  
ensembles continue to depict increased ridging and positive height anomalies  
across the eastern Pacific. The trough over northeastern North America is  
weaker in today’s models compared to yesterday’s, and would result in less of  
an impact on the week-2 forecast. The manual blend for the period depicts near  
normal 500-hPa heights across the CONUS and near to above normal heights over  
Alaska for the period as a whole, although the ridging over the East Pacific  
teleconnects with troughing over the western CONUS, which may result in  
occasional periods of below normal heights.  
 
Below normal temperature probabilities are increased across much of the eastern  
third of the CONUS, supported by the consolidation forecast tool, with the  
early part of the period forecast to have the highest chances for below normal  
temperatures. Probabilities for near to above normal temperatures are  
highlighted across the western half of the CONUS, due to increased ridging in  
the East Pacific and enhanced Pacific flow. The ECMWF and GEFS reforecast tools  
support increased chances for above normal temperatures across the central  
CONUS. However, any troughing that develops downstream of the East Pacific ridge could bring near to below normal temperatures into the region, and therefore, near normal temperatures are forecast over the Northern and Central Rockies and Plains. Probabilities for above normal temperatures also remain elevated across Alaska underneath persistent southerly mid-level flow, and consistent with the GEFS and ECMWF reforecast tools. The ECMWF and GEFS reforecast tools are in good agreement in terms of the week-2 precipitation forecast across the CONUS. Increased chances for near to above normal precipitation remain favored for most areas from the Northern Rockies and Great Plains, extending east to the Atlantic Coast, given the increased Pacific flow and periodic shortwave disturbances traversing across the central and eastern CONUS, with the highest chances closest to the Gulf of Mexico Coast due to enhanced moisture availability. Below normal precipitation probabilities are increased over much of the western CONUS due to the influence from surface high pressure forecast over the East Pacific. Near to above normal precipitation chances continue to be increased over Alaska due to troughing over the Bering Sea and the ridging over the eastern Pacific favoring a more northward storm track across Alaska. The official 8-14 day 500-hPa height blend consists of: 30% of Today's 6z GFS Ensemble Mean centered on Day 11, 50% 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: Below average, 2 out of 5, due to good agreement in the dynamical models, offset by a predicted low amplitude pattern. FORECASTER: Thomas Collow 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: 19540415 - 20010519 - 19580504 - 19810422 - 20080507 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: 19540415 - 19810425 - 20080506 - 20010518 - 19690418 6-10 DAY OUTLOOK TABLE Outlook for May 11 - 15 2021 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 N N E MONTANA N N WYOMING N B UTAH A B ARIZONA A N COLORADO N B NEW MEXICO A B N DAKOTA N N S DAKOTA N N NEBRASKA B N KANSAS B A OKLAHOMA B A N TEXAS B A S TEXAS N A W TEXAS B N MINNESOTA N N IOWA B N MISSOURI B N ARKANSAS B A LOUISIANA N A WISCONSIN B B ILLINOIS B N MISSISSIPPI N A MICHIGAN B B INDIANA B B OHIO B B KENTUCKY B N TENNESSEE B A ALABAMA B A NEW YORK B B VERMONT B N NEW HAMP B N MAINE B N MASS B N CONN B N RHODE IS B N PENN B N NEW JERSEY B N W VIRGINIA B N MARYLAND B N DELAWARE B N VIRGINIA B N N CAROLINA B A S CAROLINA B A GEORGIA N A FL PNHDL N A FL PENIN A A 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 N N 8-14 DAY OUTLOOK TABLE Outlook for May 13 - 19 2021 STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A N OREGON A N NRN CALIF A B SRN CALIF A N IDAHO A B NEVADA A B W MONTANA N N E MONTANA N N WYOMING N B UTAH A B ARIZONA A B COLORADO A B NEW MEXICO A B N DAKOTA N A S DAKOTA N A NEBRASKA N A KANSAS N N OKLAHOMA N A N TEXAS N A S TEXAS A A W TEXAS A N MINNESOTA N A IOWA N A MISSOURI N A ARKANSAS B A LOUISIANA B A WISCONSIN N A ILLINOIS N A MISSISSIPPI B A MICHIGAN N A INDIANA B A OHIO B A KENTUCKY B A TENNESSEE B A ALABAMA B A NEW YORK B A VERMONT B N NEW HAMP B A MAINE B A MASS B A CONN B A RHODE IS B A PENN B A NEW JERSEY B A W VIRGINIA B N MARYLAND B A DELAWARE B A VIRGINIA B N N CAROLINA B N S CAROLINA B N GEORGIA B N FL PNHDL N N FL PENIN A N AK N SLOPE A N AK ALEUTIAN N A AK WESTERN A A AK INT BSN A N AK S INT N A AK SO COAST N A AK PNHDL N N 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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