The forecasts depicted below combine WPC forecasts of fronts, isobars and high/low pressure centers with the NDFD depiction of expected weather type for days .5 to 2.5 ahead. Each frame represents 6 hours. A short range forecast discussion for the CONUS is available below the short term loop.
Short Term Forecast Frontal Systems and Isobars Loop
Short Range Forecast Discussion
FXUS01 KWBC 210522 PMDSPD Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 1221 AM EST Sat Dec 21 2024 Valid 12Z Sat Dec 21 2024 - 12Z Mon Dec 23 2024 ...Periods of moderate to heavy rainfall near the Pacific Northwest and northern California... ...Record warmth possible across parts of the West Saturday and Sunday... The general flow pattern favors an upper level trough across the eastern Pacific ocean, ridging aloft in the West, and troughing aloft in the eastern United States. The consequence of this pattern will be some rainfall along the West Coast, warmth across the Intermountain West, and cold across portions of the East. Starting out West, skirmishes of rain along the West Coast are expected Saturday as low pressure systems move northward offshore the West Coast. On Saturday and Sunday, weakening fronts move eastward, pushing a couple batches of rainfall into the through the Pacific Northwest, northern Intermountain West, and northern California, with snowfall expected at higher elevations. Some periods of high winds are expected -- high wind warnings are in effect for areas of northern California and southern Oregon. High temperatures across northern portions of the West will rise into the 40s and 50s, high enough to threaten record high temperatures on Saturday. Across the Southwest, high temperatures should rise into the 70s to 80s Saturday and 60s to 70s on Sunday, threatening daily record high temperatures in and near southern Arizona and southern California. Mid-continent, a seasonably strong and cold high pressure system migrates from the Great Lakes into the East, bringing below average temperatures near and to its east. For some areas of the East, it should be the coldest temperatures thus far this winter. Freeze Watches and Cold Advisories have been posted for sections of northern Florida and southeast Georgia for the incoming cold. When combined with cyclonic flow around a low moving offshore the East Coast, lake effect snowfall is expected near the Great Lakes, portions of the Appalachians, northern Mid-Atlantic States, and New England which slowly fades Saturday and Sunday. Winter weather advisories are in effect in patches across the eastern Great Lakes, Central/Southern Appalachians, northern Mid-Atlantic States, and coastal New England with a very localized Winter Storm Warning is in place for portions of Downeast Maine through midday Saturday to help advise on the moderate to heavy snowfall expected. A low pressure system developing across the Upper Midwest and Great Lakes Sunday into early Monday is expected to lead to snowfall which increases in coverage and intensity with time from North Dakota eastward into Michigan. Roth Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php $$
Depicted Weather Types
- NDFD Rain (Chance) – There is chance of measurable rain (≥0.01″) at the valid time.
- NDFD Rain (Likely) – Measurable rain (≥0.01″) is likely at the valid time.
- NDFD Snow (Chance) – There is chance of measurable snowfall (≥0.01″ liquid equivalent) at the valid time.
- NDFD Snow (Likely) – Measurable snow (≥0.01″ liquid equivalent) is likely at the valid time.
- NDFD Mix (Chance) – There is a chance of measurable mixed precipitation (≥0.01″ liquid equivalent) at the valid time. “Mixed” can refer to precipitation where a combination of rain and snow, rain and sleet, or snow and sleet are forecast.
- NDFD Mix (Likely) – Measurable mixed precipitation (≥0.01″ liquid equivalent) is likely at the valid time. “Mixed” can refer to precipitation where a combination of rain and snow, rain and sleet, or snow and sleet are forecast.
- NDFD Ice (Chance) – There is a chance of measurable sleet and/or freezing rain (≥0.01″ liquid equivalent) at the valid time.
- NDFD Ice (Likely) – Measurable sleet and/or freezing rain (≥0.01″ liquid equivalent) is likely at the valid time.
- NDFD T-Storm (Chance) – There is a chance of thunderstorms at the valid time. Areas are displayed with diagonal hatching enclosed in a dark red border.
- NDFD T-Storm (Likely and/or Severe) – Thunderstorms are likely and/or the potential exists for some storms to reach severe levels at the valid time.