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Composite Map Day 8-14

Experimental Probabilistic Outlooks Temperature Hazards Precipitation Hazards Wind Hazards Snow Hazards

Valid Saturday February 04, 2023 to Friday February 10, 2023

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EST January 27 2023

Synopsis: Surface high pressure is expected to briefly result in an increased risk of much-below normal temperatures across the Northeast on February 4 and 5. A low pressure system, with enhanced onshore flow, is forecast to track eastward from the Pacific Northwest to the northern Rockies from February 4 to 6. Beginning on February 8, mid-level high (low) pressure is expected to build over Alaska (western U.S.)

Hazards

• Moderate risk of much below-normal temperatures for parts of the Northeast, Sat, Feb 4.
• Slight risk of much below-normal temperatures for the Northeast, Sat-Sun, Feb 4-5.
• Slight risk of much below-normal temperatures for the northern Great Plains, Wed-Fri, Feb 8-10.
• Slight risk of heavy precipitation for portions of California, Oregon, and Washington, Sat-Mon, Feb 4-6.
• Slight risk of heavy snow for northern Coastal Range, Cascade Range, Sierra Nevada Mountains, and Northern Rockies, Sat-Mon, Feb 4-6.
• Slight risk of high winds for portions of California, Oregon, and Washington, Sat-Mon, Feb 4-6.
• Slight risk of heavy precipitation for eastern Oklahoma and Texas, lower Mississippi Valley, and Ohio to Tennessee Valleys, Wed-Fri, Feb 8-10.

Detailed Summary

For Monday January 30 - Friday February 03: WPC Days 3-7 U.S. Hazards

For Saturday February 04 - Friday February 10: A short-lived and transient outbreak of Arctic air is forecast for the Northeast on Feb 4 and 5, as a deep anomalous 500-hPa trough rotates through southeastern Canada. On Feb 4, a moderate risk of much below-normal temperatures is posted for northern New York and New England where the reforecast tools depict minimum temperatures having a 40 percent chance of falling below the 15th percentile. Uncalibrated model solutions feature minimum temperatures below -10 degrees F in the outlined area for a moderate risk. A slight risk of much below-normal temperatures continues through Feb 5, but beyond this time, a rapid warming trend is likely with above-normal temperatures forecast across the East by Feb 8.

Moderating temperatures are expected across the central U.S. by Feb 4 as the core of Arctic air rapidly shifts eastward. Later in week-2, the ensemble means are converging on a more typical La Nina pattern with an amplifying ridge over the Aleutians and Bering Strait with a downstream trough across western North America. Model solutions are in better agreement with a full-latitude ridge becoming established over Alaska and extending poleward, which would eventually bring a renewed outbreak of Arctic air to at least the north-central U.S. by mid-February. Given this evolving pattern along with support from reforecast tools and uncalibrated temperature output, a slight risk of much below-normal temperatures is posted for the northern Great Plains from Feb 8 to 10.

The GFS and ECMWF ensemble means remain consistent that a shortwave trough progresses eastward from the northeastern Pacific to the Pacific Northwest and northern Rockies early in week-2. This shortwave trough, reforecast tools, and uncalibrated model output support a slight risk of heavy precipitation and snow across the Pacific Northwest, northern California, and the northern Rockies from Feb 4-6. The enhanced onshore flow, associated with the shortwave trough, also results in a slight risk of high winds for the Pacific Northwest and northern California. In response to the amplifying ridge upstream over the north-central Pacific and Alaska, a longwave trough is expected to develop across the West later in week-2. Downstream of this longwave trough axis along with return Gulf moisture, there is an increasing risk of heavy precipitation for the south-central U.S. and a corresponding hazard is posted from Feb 8 to 10. Although a heavy snow hazard is not posted for the north-central U.S. due to weak signals at this time, the evolving longwave pattern would begin to increase a winter storm risk for this region by mid-February.

The week-2 temperature outlook for Alaska will be dependent on the longitudinal placement of the amplifying ridge axis. Southeastern Alaska is the most likely area to experience below-normal temperatures with model solutions depicting an Arctic surface high centered to the east. Since the signal for much below-normal temperatures is relatively weak, a temperature hazard is not posted at this time.

Forecaster: Brad Pugh

$$ Please consult local NWS Forecast Offices for short range forecasts and region-specific information.

Resources

Week-2 Probabilistic Extremes Tool

GFS Ensemble Forecasts