Composite Map Day 8-14

Experimental Probabilistic Outlooks Temperature Hazards Precipitation Hazards Wind Hazards Snow Hazards

Valid Thursday March 27, 2025 to Wednesday April 02, 2025

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT March 19 2025

Synopsis: An active and progressive weather pattern is favored to bring a variety of potentially hazardous weather to many parts of the Contiguous U.S. (CONUS) during the week-2 period. A low pressure system is forecast to come ashore over the Pacific Northwest at the outset of week-2, move into the Great Plains and intensify by the middle of the period then track to the Great Lakes region by the end of week-2, bringing potentially heavy snow, high winds, and heavy precipitation to much of the CONUS.

Hazards

• Slight risk of episodic high winds for coastal portions of Washington, Oregon, and California north of Monterey Bay, Thu-Wed, Mar 27-Apr 2.
• Slight risk of episodic high winds for much of the central CONUS, Thu-Sun, Mar 28-31.
• Slight risk of episodic high winds for much of the eastern CONUS, Sat-Wed, Mar 30-Apr 2.
• Slight risk of periods of heavy precipitation for western portions of Washington, Oregon, and northern and central California, Thu-Wed, Mar 27-Apr 2.
• Slight risk of periods of heavy precipitation for portions of the Ohio, Tennessee, and Lower and Middle Mississippi Valleys, Sat-Mon, Mar 29-31.
• Slight risk of periods of heavy precipitation for portions of southern Texas, Thu-Sat, Mar 27-29.
• Slight risk of periods of heavy snow for the Cascade, Klamath, and Sierra Nevada Mountains, Thu-Wed, Mar 27-Apr 2.
• Slight risk of periods of heavy snow for the Northern Rockies, Thu-Wed, Mar 27-Apr 2.
• Slight risk of periods of heavy snow for the Central Rockies, Sat-Wed, Mar 29-Apr 2.
• Slight risk of periods of heavy snow for portions of the Northern Plains, Upper Mississippi Valley, and Upper Great Lakes region, Sat-Tue, Mar 29-Apr 1.
• Slight risk of periods of heavy snow for much of New England and Lower Great Lakes region, Sat-Tue, Mar 29-31.
• Risk of Rapid Onset Drought for portions of the Southern Plains.

Detailed Summary

For Saturday March 22 - Wednesday March 26: WPC Days 3-7 U.S. Hazards

For Thursday March 27 - Wednesday April 02: oday’s ensemble model solutions continue to show good agreement on the synoptic pattern as depicted in 500-hPa height anomalies, and have had good day-to-day continuity as well. However, there remains some uncertainty with regard to the intensity and evolution of surface features, particularly the potential for strong cyclogenesis event forecast to unfold during the middle of week-2. Ensemble solutions depict persistent mid-level troughing over the North Pacific and Northeast U.S. and transient shortwaves passing over the rest of the CONUS through the week-2 period.

Multiple model solutions depict persistent troughing at the surface and aloft over the North Pacific resulting in a steady moist onshore flow prevailing over the Pacific Northwest. The integrated vapor transport (IVT) tool indicates very high probabilities of IVT to exceed 150 kg/m s from both the ECMWF and GEFS throughout week-2, particularly after day-10 (Mar 29). The precipitation Probabilistic Extremes Tools (PETs) from the ECMWF and GEFS show a more coherent signal than yesterday with regard to the potential for heavy precipitation over the West Coast, indicating at least a 20% chance of 3-day precipitation totals exceeding the 85th percentile climatologically and at least 1 inch well into central California. Therefore a slight risk of periods of heavy precipitation is posted for portions of the West Coast as far south as Monterey Bay for March 27-Apr 2. A slight risk of heavy snow is also posted for the Cascade, Klamath, and northern Sierra Nevada Mountains for the same period, as well as a slight risk of high winds along the coast from the Canadian border to Monterey Bay.

A shortwave trough is anticipated to move over the West Coast and the Intermountain West and into the central CONUS over the course of week-2. This is anticipated to result in the aforementioned Pacific moisture getting pushed further inland, favoring enhanced snow for the Northern Rockies. The uncalibrated ECMWF ensemble indicates enhanced probabilities of 3-day snowfall exceeding 6 inches throughout week-2, thus a slight risk of heavy snow is posted for Mar 27-Apr 2 for much of the Northern Rockies. As week-2 progresses and moisture transport from the Pacific is favored to increase, the chance for heavy snow spreads southward, warranting a slight risk of heavy snow for much of the Central Rockies for Mar 29-Apr 2.

As this surface low pressure system pushes further eastward, ensembles depict another round of strong lee cyclogenesis over the Great Plains during the middle of the week-2 period. Model depictions of MSLP anomalies indicate a strong pressure gradient setting up over the Great Plains by March 28, resulting in strong southerly flow and the enhanced potential for high winds at the surface. The PETs for maximum wind speed show a better signal than yesterday with regard to the potential for extremes in wind speed, now indicating widespread chances of maximum wind speed exceeding the 85th percentile across the Great Plains by Mar 28, then spreading eastward into the Mid-Atlantic and Northeast U.S. by the end of week-2. This, along with a favorable synoptic setup and consistent model depictions of strong cyclogenesis occurring over the Great Plains, warrants a slight risk of high winds to be posted for much of the central CONUS for Mar 28-31, along with most of the eastern CONUS excluding only portions of the Southeast U.S. for Mar 30-Apr 2.

Multiple ensemble solutions also indicate the possibility of heavy precipitation developing ahead of this system as it winds up and draws in Gulf moisture. Early in week-2 model solutions indicate enhanced potential for convection in South Texas, which is also supported by the GEFS and ECMWF PETs for precipitation, indicating at least a 20% probability of 3-day precipitation totals exceeding the 85th percentile and at least 0.5 inch, so a slight risk of heavy precipitation is posted for much of South Texas for Mar 27-29. Further east, there continues to be modest support from the PETs indicating at least a 20% chance of 3-day precipitation totals exceeding the 85th percentile for Mar 29-31, with the ECMWF being more bullish than the GEFS. While there is some spread among model solutions regarding the details, once again the overall good agreement on a favorable synoptic pattern, thus warranting the issuance of a slight risk of heavy precipitation for portions of the Ohio, Tennessee, and Lower and Middle Mississippi Valleys for Mar 29-31. On the other hand the GEFS PET for snow water equivalent (SWE) has a stronger signal, indicating at least a 20% chance of 3-day SWE exceeding the 85th percentile for portions of the northern CONUS as this system strengthens. Uncalibrated ECMWF probabilities for snowfall have been consistently indicating the potential for heavy snow for the Northern Plains and today increased coverage to include northern portions of the Great Lakes region and New England. Slight risks for heavy snow are posted for portions of the Northern Plains, Upper Mississippi Valley, and Upper Great Lakes region for March 29-Apr 1, and for portions of the Lower Great Lakes region and Northeast U.S. for Mar 29-31.


Much of the southern and southwestern CONUS has been experiencing below-normal precipitation for some time now, a trend that is unfortunately favored to continue through the week-2 period. A risk of Rapid Onset Drought (ROD) remains posted for portions of eastern New Mexico and northern Texas, due to antecedent dry conditions and anticipated precipitation deficits. There are insufficient indications among the forecast tools to warrant a risk of much above-normal temperatures for today’s week-2 hazards outlook, but nonetheless very anomalously warm temperatures are likely for portions of the Rio Grande Valley and Big Bend regions. Anticipated above normal temperatures combined with below-normal precipitation and enhanced wind speeds increases the potential for wildfires throughout the week-2 period.

Forecaster: Danny Barandiaran

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

Resources

Week-2 Probabilistic Extremes Tool

GFS Ensemble Forecasts