Time is flying by so far in 2025! We are already onto the second and shortest month of the year, and each February likes to bring a variety of weather impacts to the state- from thunderstorms and warmth to raging winter storms. Within this outlook, I will outline all of the forecast variables I used to put this monthly forecast together and what we should expect to see in terms of temperatures, precipitation, and snowfall anomalies. Let’s jump into it!
JANUARY RECAP:
In general, January 2025 was an overall dry and cold month. Liquid-equivalent precipitation (including melted snow) was well below average, with much of the state receiving 5-75% of normal precipitation for the month. In contrast, it was quick the cold month as well with temperatures running as much as 3 to 10 degrees below average, marking one of the coldest Januarys in over a decade.
Despite the limited liquid-equivalent precipitation across the state, there was a lot of snow to go around the state. Much of western and south-central Pennsylvania ended up receiving more snow than average, with percent of normal as much as 150-300% across portions of southwestern and northwestern Pennsylvania. This is due to the constant northwesterly flow and warmer lakes, allowing for days upon days of snowfall. Those across northeastern Pennsylvania missed out on the lake effect and synoptic snowstorms, in which snowfall amounts fell below average for the month.
FEBRUARY OUTLOOK:
One of the best ways to forecast for the future is to look back at recent patterns in previous years. Here are the years I researched upon that had similar patterns in January that could translate to the patterns in February, based on ENSO (La Nina this year) and other background teleconnection patterns such as the EPO and TNH. The years I am using for the analogs are shown below.
If we stack all of these years together and output precipitation and temperature anomalies, here is how they rounded out to be. In terms of precipitation, these analog years were very wet across the state and much of the local region (wet could mean rain *OR snow). To the right, the temperature anomalies are leaning toward below-average temperatures, although the greatest cold from these years was bottled up in the north-central Plains. There is also a clear signal for southeast ridging, with the dry and warmer anomalies showing up in the southeast US, which may become a problem for our winter weather events.
With these same years in mind, here is how the upper-air pattern flow and temperature anomalies shaped up to be. The general flow is showing a stout eastern Pacific ridge with roughing across much of the central United States, providing a flow of colder air into the region. The greatest anomaly for the coldest airmass is showing up in the northern Plains and south-central Canada with a generally warmer airmass across the southeast and eastern US. This lines up well with the surface temperature anomalies in the previous graphic.
In terms of snowfall with the analog years, there is a lot of spread. Overall, more of these years brought above-average snowfall than not, although the recent analog year of 2022 brought little snowfall to much of the state. However, amongst all of these years, outside of 2014, the best-favored areas for snow will be along and north of I-80, with increased ice/sleet events along and south of I-80. This is more than likely due to the influence of the southeastern ridge, allowing for warmer air to intrude into the region.
TELECONNECTIONS:
Now, let’s begin to look at some of the forecasted teleconnections as we head into the month. The first I want to look at is the MJO (Madden-Julian Oscilliation). The MJO refers to a large-scale atmospheric disturbance that manifests as an eastward-moving pulse of clouds, rainfall, and winds near the equator, typically recurring every 30 to 60 days, significantly impacting tropical weather patterns on a weekly to monthly timescale; essentially, it’s a “wave” of convective activity traveling across the Indian and Pacific Oceans, with distinct phases of enhanced rainfall followed by suppressed rainfall. These convective patterns influence our jet stream and correlate well with our temperature and precipitation anomalies! Right now, the MJO is quickly swinging through phases 4-5-6, which are generally the ‘warmer’ phases in our region. This is a good reason why we have seen a break from our extreme cold in mid-January. However, as we swing later into the month of February, especially after the 10th, the signal is increasing for the MJO to swing through phases 7-8-1, that are more favorable for cold and snow across the region. This is an important role in the monthly forecast and something to keep an eye out for!
Shown below are two other important teleconnections. The EPO (Eastern-Pacific Oscillation) and the NAO (Northern Atlantic Oscillation). These teleconnections are measured in either positive or negative phases- unlike the MJO which goes through numbered phases. The EPO refers to a weather pattern characterized by variations in atmospheric pressure over the eastern Pacific Ocean. A negative EPO increases the risk for colder air to infiltrate into the central and eastern US and has helped to dominate the pattern throughout December and January. The North Atlantic Oscillation (NAO) Index describes changes in the strength of two recurring pressure patterns in the atmosphere over the North Atlantic: a low near Iceland, and a high near the Azores Islands. The North Atlantic Oscillation (NAO) Index describes changes in the strength of two recurring pressure patterns in the atmosphere over the North Atlantic: a low near Iceland, and a high near the Azores Islands. A negative NAO helps to ‘block’ the pattern across North America, which could increase the risk for larger rain or snowstorms and even help to ‘lock in’ colder air if it is already in place. In contrast, a positive NAO supports a more transient and fast-flowing pattern, which limits the intensity of cold air and storm events.
Two more important teleconnections, the PNA (Pacific-Northern America Oscillation) and the AO (Arctic Oscillation). The PNA influences regional weather by affecting the strength and location of the East Asian jet stream, and subsequently, the weather it delivers to North America. The negative phase of the PNA supports more storminess and troughing across the western US, which usually coorelates to warmer conditions with rdiging across the eastern US. This will also allow for an active pattern with increasing storms sliding from the western US into the central/eastern US. However, since we are coupling the -PNA with a -EPO and possibly a -NAO and -AO, the active storm track will allow for more wintry events than rain events with cold air pressing onto the region. The AO (Arctic Oscillation) which refers to a large-scale atmospheric circulation pattern over the Arctic region that significantly influences weather patterns in the mid-latitudes of the Northern Hemisphere. The AO is expected to remain positive and then head into the negative phase, which allows for cross-polar flow between the Arctic and North America region, increasing the risk for cold risks into the central and eastern US.
In conclusion, the teleconnections are expected to remain favorable for colder air to press into the north, central, and possibly portions of the eastern US due to the MJO 7-8-1, -EPO, -NAO, -PNA, and neutral AO heading into the month of February, I am liking the idea of colder air outbreaks spilling into the region, combined with a more active than normal storm track.
Another important component to look at is the polar vortex. The polar vortex is situated at around the 10mb layer in the atmosphere, which is 50,000 feet or about 9-10 miles above the North Pole of North America. In fact, it is so high up it is situated in the stratosphere, and not the troposphere where our weather occurs. The strength and position of this polar vortex, despite being above the troposophere, helps to dictate our winter weather at times, especially if it couples with the troposphere. A strong, coupled polar vortex helps to keep the cold air locked in the Arctic regions while a weaker, wavy polar vortex allows for very cold air outbreaks to spread across the Northern Hemisphere. As of recent, model guidance is hinting at a split of the polar vortex due to anomalous ridging in the stratosphere within the next 7-10 days. This could either allow the polar vortex to stretch or split. Depending on if we see a direct coupling with the trosphere, it is possible we could see effects from the stretch or split within the next 10-20 days, increasing the risk for colder air to intrude across North America and possibly our region.
MODEL PROJECTIONS:
On top of analogs and teleconnections, it is also good to look at what long-range models are projecting. Shown first is the GFS extended model. The GFS extended is projecting a well-above precipitation pattern with temperatures leaning above average. The precipitation pattern fits well with the analogs, but it is leaning a bit warmer on the temperatures.
The ECMWF extended guidance is falling the same fit as the GFS extended, with well-above precipitation expected with temperatures running around average, leaning slightly above average.
PA WEATHER PLUS FORECAST:
Starting off with temperatures, I am expecting a cooler-than-average month for the northern tier of the state (1-3degF below average) with near-average temperatures with temperature swings expected across the southern tier (+0.5 to -0.5 compared to average). Due to the extension of the southeast ridge coupled with cold air outbreaks, the magnitude of the higher temperature may outpace the lower temperatures across this region.
I believe with the -PNA and a tight temperature gradient through our region, we will be in for an active storm track. I am expecting above average (125-150%) to well above average (150-200%+) precipitation. Keep in mind, that this precipitation forecast includes both rainfall and snowfall. I expect a mixture of these events throughout the month, but this will be much needed after a rather dry January.
I am keeping an eye on the risk for increased ice events across much of central and northern Pennsylvania, where these regions may be favored for ‘cold air damming’ events with colder air to the north. At times, the southeastern ridge will help to pump in warmer air aloft, although temperatures at the surface will lag behind. A few sleet/freezing rain events cannot be ruled across these areas, which may be very hazardous in terms of travel conditions.
At last, the snowfall forecast. With the expectation of an active storm track and increasing risks for colder conditions, I am expecting a snowy month, especially across the central and northern tier. Well above snowfall is expected across the far northern tier (150-200%+) especially north of I-80, where we will see a limitation of mixed weather events. Farther south, above-average (125-150%) snowfall is expected. Expect a mixture of snow and mixed events, although one larger snowfall event may push these areas above average. Across the far southern counties, due to the extension of the southeastern ridge, these areas may mix with sleet and rain at times, allowing for less snowfall. (85-115%) of average snowfall is expected across those areas.
In conclusion, be prepared for an active month! We will likely be battling between cold air outbreaks and the southeastern ridge, allowing for lots of ups and downs with day-to-day temperatures. In addition, an active storm track will allow for increased precipitation, including snow, ice, and rain. It is crucial you stay up-to-date with the latest information with possible weeks with multiple weather events. If you have any questions, feel free to reach out at any time!
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