Prognostic Discussion for Monthly Outlook 
NWS Climate Prediction Center College Park MD 
300 PM EST Sun Feb 28 2021 
 
 
30-DAY OUTLOOK DISCUSSION FOR MARCH 2021 
 
The updated March 2021 temperature and precipitation outlooks are not too 
significantly changed from the previous mid-month outlook. The updated outlooks 
utilized the latest short-range, medium-range, extended-range and subseasonal 
dynamical model forecast guidance for some adjustments. In addition, the most 
recent assessment of boundary conditions (anomalous soil moisture and snow 
cover), the MJO state and the AO state are also considered in making the 
update. 
 
The uncertainty whether short-range forecasts of a change to a positive AO 
phase would persist and be supported by changes in stratosphere troposphere 
interaction have been removed as the extended range forecasts of the AO support 
continuation of the current positive AO phase through at least mid-month. 
 
The MJO influence described at mid-month, however, remains in play as 
predictions of the MJO signal (i.e., RMM) are forecast to shift from Phase 5/6 
(Indonesia/far western Pacific) to potentially Phase 8/1 over the next two 
weeks. This increases uncertainty in the temperature outlook some for the Great 
Lakes, Ohio Valley and Northeast as the odds for below-normal temperatures 
would increase for the 3rd and 4th weeks of March. This is strongly at adds 
with the latest Week 3-4 dynamical model guidance which continues persistence 
of favored above-normal temperatures for the eastern two-thirds of the CONUS 
from Week-2. 
 
Anomalous snow cover and depth remains strongly negative across the northern 
plains as noted in the mid-month outlook. Soil moisture anomalies are likely to 
become increasingly positive for areas in the lower Mississippi Valley, the 
Tennessee Valley and lower Ohio Valley as a combination of antecedent 
conditions from recent snowmelt and heavy rains in some areas prior to the 
start of the month. 
 
Based on the above factors, the updated March 2021 temperature outlook keeps 
elevated odds for monthly mean below-normal temperatures for southern Alaska, 
and the Far West - which is a more narrow area than the mid-month outlook 
depiction. Above-normal monthly mean temperatures remain favored for the 
eastern two-thirds of the CONUS, however, there are some changes. First, 
above-normal temperatures in the Southwest were shifted eastward in the updated 
outlook and probabilities across the northern Plains and Great Lakes are 
increased. Lower probabilities are located in a zonal swath for the Tennessee 
and lower Ohio Valley's due to possible impact from above-normal surface 
wetness and also along the eastern seaboard due to cooler temperatures forecast 
early in the month and also due to the potential impact from the MJO, albeit 
highly uncertain. 
 
For precipitation, the latest dynamical model guidance, especially in the short 
term help better focus favored above-normal precipitation in the Tennessee 
Valley at the start of the month of March. This region and areas northward to 
the Great Lakes are slightly modified from the half month lead outlook. 
Below-normal precipitation is highlighted from the interior West and Southwest 
eastward to the central and southern Plains and along the Gulf Coast and 
Florida. Changes in these regions from the earlier outlook include removal of 
the slightly elevated odds for above-normal precipitation in the northern 
Rockies, removal or reducing of chances for below normal precipitation for 
parts of California and the central and southern Great Basin and Rockies. A 
strong jet forecast to impinge western Alaska through at least the first half 
of the month, favors elevated odds for above-normal precipitation for much of 
Alaska with removal of the small region of elevated odds for below-normal 
precipitation along the Alaska south coast in the mid-month outlook. 
 
**************************************************************************** 
*** Previous mid-month discussion below *** 
**************************************************************************** 
 
As we approach the month of March, the pattern across the greater North America 
region appears to be in the process of changing from the last few weeks. Week 2 
dynamical model forecast guidance supports a change to anomalous ridging over 
the north central Pacific with the central North America mean trough shifted 
westward and deepening over portions of western North America including into 
western CONUS. Downstream of this, more amplified ridging and positive 500-hPa 
height departures are forecast for much of the southeast U.S. favoring a more 
southwesterly-westerly mean flow for the eastern half of the CONUS then in 
recent weeks. 
 
The most recent Week 3-4 guidance from the CFS, ECMWF and extended GEFS support 
a continuation of this change, in the mean, for approximately the first two 
weeks of March. March CFS forecasts as well as those from the majority of the 
NMME and Copernicus model suites also favor this pattern and associated 
anomalous temperature and precipitation patterns which are consistent with 
typical La Nina conditions in many ways during this point in the seasonal 
cycle. 
 
Other factors to consider in addition to a review of the available dynamical 
model guidance across time scales, is the state and forecast evolution of the 
MJO, the AO and most recent anomalous snow cover. 
 
The MJO has been active during January and February resulting in both 
constructive and destructive interference with La Nina impacting anomalous 
tropical rainfall, circulation and other variables in the Pacific basin. 
Forecast information suggests that the MJO is likely to weaken or become less 
coherent entering March and is not strongly utilized in the March outlook due 
to this as well as indications that much of recent mid-latitude temperature and 
precipitation anomalies have most likely been driven by high latitude 
subseasonal variability. 
 
Predictions in the short-term (next 10 days) indicate the phase of the AO 
(which has returned to near zero) to remain near zero or weakly positive in the 
mean as compared to the strongly negative phase of the last couple months. The 
Sudden Stratospheric Warming (SSW) of early-mid January would continue to 
elevate odds for a negative AO phase into the month of March resulting in the 
continuation of potential cold air outbreaks into the mid-latitudes. There is 
high uncertainty, however, in whether the negative phase of the AO will return 
and persist and if so where troughing and so favored below-normal temperatures 
are most likely to develop at forecast lead times well into the month of March. 
 
Finally, substantially below-normal snow cover and snow depth exist across 
parts of the northern Plains and upper Mississippi Valley. Although, early in 
the seasonal cycle, taken alone, this is likely to favor above-normal 
temperatures in these areas. 
 
After consideration of the factors described above, the March temperature 
outlook favors monthly mean below-normal temperatures for a region stretching 
from south-central Alaska southeastward to include northern California, the 
Pacific Northwest and the northern Rockies. This is strongly supported by 
dynamical model guidance across time scales and is consistent with La Nina 
conditions. Elevated probabilities for above-normal temperatures are depicted 
for parts of the north and west coast of Alaska based on negative sea ice and 
positive ocean surface temperature trends  especially later in the month of 
March. 
 
Dynamical model guidance and in some cas es typical La Nina conditions and 
positive temperature trends  favor above-normal temperatures for a region from 
the Southwest eastward to include the southern CONUS and northward to encompass 
the central Mississippi Valley, eastern Great Lakes, Ohio Valley and eastern 
seaboard. Only slightly tilted odds of above-normal temperatures or 
Equal-Chances (EC) are depicted for the northern and central Plains, central 
and upper Mississippi Valley and parts of the Ohio Valley, Great Lakes and 
Tennessee Valley due to the uncertainty and conflicting indicators described 
above with respect to the phase of the AO, anomalous snow cover and snow depth 
and dynamical model guidance. 
 
For precipitation, below-normal monthly total precipitation amounts are most 
likely for the southern tier of the CONUS with some expansion of this 
highlighted area to the central Great Plains, primarily based on dynamical 
model guidance which is consistent with La Nina typical impacts. For similar 
reasons, elevated odds for above-normal precipitation is forecast for a small 
region in the northern Rockies and for the Ohio Valley and Great Lakes region. 
For Alaska, elevated odds for above-normal precipitation is depicted for parts 
of the north and west coasts associated with anticipated more open and warmer 
waters in nearby areas as well as typical La Nina impacts. Below-normal 
precipitation is most likely for the south-central coast and far northern 
Alaska Panhandle. 
 
FORECASTER: Jon Gottschalck 
 
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. 
 
The next monthly outlook...for Apr ... will be issued on Thu Mar 18 2021 
 
These outlooks are based on departures from the 1981-2010 base period. 
$$