Prognostic Discussion for Monthly Outlook
NWS Climate Prediction Center College Park MD
830 AM EST Thu Jan 21 2021


30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2021

The February 2021 temperature and precipitation outlooks are based on Weeks 3 
to 4 forecasts from the CFS and ECMWF models, the North American Multi-Model 
Ensemble (NMME), typical influences from the ongoing La Niña, and decadal 
trends. Below average sea surface temperatures (SSTs) across the equatorial 
Pacific along with a strong coupling with the atmosphere represent La Niña 
conditions. Although dynamical models depict a strengthening Madden-Julian 
Oscillation (MJ0) during late January into early February, La Niña is likely to 
be the major tropical forcing due to the well-established anomalous enhanced 
(suppressed) convection over the Maritime Continent (equatorial Central 
Pacific).  
 
Despite high latitude blocking with a persistent negative Arctic Oscillation 
(AO), 30-day temperatures since mid-December have averaged above normal for 
nearly all of the CONUS. This mild temperature pattern was due in part to 
enhanced Pacific flow overspreading the higher latitudes of North America and 
cross polar flow generally limited to the Eastern Hemisphere. Week-2 model 
guidance (Jan 28-Feb 3) remains consistent that an amplified and full-latitude 
500-hPa ridge becomes centered over the Aleutians and extends poleward. The 
Week 3-4 ECMWF model indicates this anomalous ridging persisting through at 
least early February, which is likely to promote cross polar flow and result in 
below normal temperatures across parts of Alaska. Based on good model 
continuity with this feature and support from a number of inputs to the NMME, 
below normal temperatures are favored for southeastern Mainland Alaska and the 
Alaska Panhandle. Although the source region is expected to become more 
favorable for Arctic air to shift south across the western and north-central 
CONUS during the next month, the NMME supports equal chances (EC) of below, 
near, or above normal temperatures for much of the West and Northern Great 
Plains. Sparse snow cover across the Canadian Prairies and Northern Great 
Plains may be a limiting factor to anomalously cold temperatures heading into 
February. Below normal temperatures are slightly favored for parts of the 
Pacific Northwest and Northern Rockies, due to the predicted close proximity of 
anomalous cold during the first half of February and this is also consistent 
with La Niña composites.
 
The largest probabilities (above 50 percent) of above normal temperatures are 
forecast from the Rio Grande Valley eastward to the Gulf Coast, based on the 
week 3-4 model guidance, calibrated NMME, and La Niña composites. Although a 
high latitude block over the Davis Strait and negative phase of the NAO are 
forecast to promote periods of below normal temperatures along the East Coast 
during the remainder of January, the GFS ensemble members depict a transition 
to a neutral or even positive phase of the NAO by the beginning of February. As 
the negative NAO diminishes during the next two weeks, La Niña is expected to 
become a more dominant factor which increases probabilities of above normal 
temperatures across the Southeast. Above normal temperatures are only slightly 
favored for the Northeast, Great Lakes, and Upper Mississippi Valley due to 
lower forecast confidence and the potential for a variable temperature pattern 
during February. It remains unclear when or even if the recent stratospheric 
warming event would influence temperatures across the CONUS and this will be 
reassessed for the updated outlook released on January 31. 
 
The precipitation outlook for February is consistent with La Niña composites 
and supported by the NMME. Below normal precipitation is most likely across the 
southern tier of the CONUS, while above normal precipitation is favored from 
the Pacific Northwest eastward to the Upper and Middle Mississippi Valley and 
Great Lakes. Elevated probabilities of below normal precipitation, forecast for 
southeastern Mainland Alaska and the Alaska Panhandle, are consistent with 
below normal temperatures favored for these areas. A majority of inputs to the 
NMME support increased probabilities of above normal precipitation across the 
Aleutians. Probabilities throughout the forecast domain are tempered due to 
large uncertainties during this monthly outlook time range.

FORECASTER: Brad Pugh

The climatic normals are based on conditions between 1981 and 2010, following
the World Meteorological Organization convention of using the most recent 3 
complete decades as the climate reference period.  The probability anomalies
for temperature and precipitation based on these new normals better represent
shorter term climatic anomalies than the forecasts based on older normals.

An updated monthly outlook... for Feb will be issued on Sun January 31 2021

These outlooks are based on departures from the 1981-2010 base period.
$$