Home Site Map News Organization
Download KML
Day 3-7 Precipitation
Day 3-7 Temperature
Day 3-7 Soils
Day 8-14 Precipitation
Day 8-14 Temperature
Day 8-14 Soils
Day 8-14 Probabilistic Temperature
Day 8-14 Probabilistic Precipitation

Download Shapefiles
Day 3-7 Precipitation
Day 3-7 Temperature
Day 3-7 Soils
Day 8-14 Precipitation
Day 8-14 Temperature
Day 8-14 Soils
Day 8-14 Probabilistic Temperature
Day 8-14 Probabilistic Precipitation

Hazards Archives

About Us
   Our Mission
   Who We Are

Contact Us
   CPC Information
   CPC Web Team

HOME> Expert Assessments>Hazards Outlook

U.S. Hazards Outlook - Made March 16, 2018

 Days 3-7Days 8-14Probabilistic Days 8-14
Precipitation No Hazards
SoilsNot Available
NOTE: Dynamic map may be
delayed in updating graphics.
See static maps below this for the
most up to date graphics.

Categorical Outlooks
Experimental Probabilistic Outlooks (Information)

Valid Monday March 19, 2018 to Friday March 30, 2018

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT March 16 2018

Synopsis: A very busy period is in store for Week-1 across the entire country, before uncertainty grows in the second half of Week-2 regarding the forecast circulation, limiting confidence in subsequent hazards. Surface low pressure is forecast to be in the Central Plains at the beginning of the period, and subsequently track to the east-northeast. A second region of surface low pressure may develop off the Mid-Atlantic coast in the wake of the aforementioned system. Mid-level low pressure is forecast to approach the Pacific coastline by the middle of Week-2, favoring a wet pattern for the West and development of another surface cyclone downstream of the Northern Rockies late in Week-1. During Week-2 mid-level low pressure is forecast over the West and off the east coast, with mid-level high pressure over the Southern Plains. The latter feature is forecast to slide eastward over the course of Week-2, with uncertainty regarding the evolution of the pattern across much of the remainder of the country. Western mainland Alaska is forecast to be influenced by a region of surface low pressure tracking inland from the Bering Sea that may help bring a reinforcing shot of cold air across the state in its wake. Temperatures may moderate across the state by the second half of Week-2, while fairly dry conditions are otherwise anticipated.

Hazards Detailed Summary

For Monday March 19 - Friday March 23: By the start of the forecast period a potent surface low is forecast to be located near the Kansas-Oklahoma border, with attendant cold and warm fronts extending to the south and east, respectively. Behind the system, downslope flow across the Central High Plains appears likely to yield high winds (sustained winds above 35 knots, with possible gusts above 50 knots) on the 19th. The Storm Prediction Center (SPC) also anticipates marginally elevated fire weather conditions in association with this setup across the Southern Plains with warm, dry downslope flow and the presence of dry fuels in portions of West Texas and southeast New Mexico on the 19th. Ahead of the system, ample low-level flow out of the Gulf of Mexico is anticipated to moisten the warm sector of this system. With this moisture availability, coincident forcing mechanisms from the northward-lifting warm front, forecast steep mid-level lapse rates, and likely sufficient vertical wind shear near the triple point of the system, there is severe weather possible on the 19th of March across the Tennessee Valley and Southeast. Forecast low-level hodographs suggest tornadic supercell potential with substantial low-level helicity, despite isallobaric considerations typically being the worst modeled component for severe weather. Upscale storm growth is possible towards the overnight hours with the advancing cold front, which may shift the primary concern to severe winds. For more information on the possible severe weather threat with this system please see the SPC or your local weather forecast office. Widespread heavy rain (exceeding 1 inch in 24 hours) is possible across Alabama, Georgia, and South Carolina on the 19th with this system, with locally heavy rain possible elsewhere.

As the aforementioned system progresses to the north and east, another round of precipitation-driven threats is possible for the Mid-Atlantic and Appalachians through southern New England. Heavy snow (exceeding 6 inches in 24 hours) is possible to the north and west of the major metropolitan areas along the Interstate-95 Corridor on the 20th, with the likely exception of Boston. Cold air appears likely to be in place ahead of this event for the entire region, although much below-normal temperatures of -12 degrees F or greater appear to be confined to upstate New York and New England on the 19th and 20th. Closer to the coast, heavy rain becomes possible across the Mid-Atlantic on the 20th. Models are inconsistent in how much to deepen the low when it enters the North Atlantic, but high winds (exceeding 35 knots sustained or gusting above 50 knots) appear possible for coastal areas from the Mid-Atlantic through New England on the 20th and 21st. Models also try to spin up a secondary low pressure system off the Mid-Atlantic coast in the wake of the first system, which may bring a secondary shot of precipitation to the region.

The West is not left out of the hazardous weather in store during Week-1, with a late season atmospheric river waiting to come ashore during the period. Heavy rain (widespread totals of 1-2 inches in 24 hours) is likely for coastal portions of California between Los Angeles and the Bay area on the 21st. Further inland, heavy snows are possible across the Sierra Nevadas on the 20th and 21st where up to a couple feet of snow are possible. The primary precipitation axis is forecast to shift northward somewhat on the 21st, bringing the potential for heavy snow to mountainous areas in northwestern California and the Cascades of Oregon on the 22nd and 23rd with daily totals above 6 inches likely. Snow levels are likely to begin below mountain pass levels and rise over the course of the event given the southwesterly flow off the Pacific.

With mid-level troughing shifting into the Western U.S. and bringing the aforementioned precipitation to points closer to the coast, this setup favors cyclogenesis in the lee of the Central Rockies. Today's 12Z GFS develops a surface low over Montana by 0Z on the 23rd that is then forecast to track eastward. As it does, heavy snow is possible on the north side of the system on the 23rd across the Dakotas and into Minnesota. On the back side of the system, high downslope winds are possible across much of the High Plains also on the 23rd. As with the system earlier in the week, adiabatic warming and drying are likely with this downslope flow that may help raise fire weather concerns across the High Plains, although SPC outlooks currently do not extend to this forecast lead.

Alaska is forecast to be impacted by a region of surface low pressure approaching the state from the Bering Sea early in Week-1. This may yield an area of high winds (exceeding 35 knots) on the 19th for areas surrounding the Norton Sound. In the wake of this system, Arctic air appears likely to spill southward across the state. The cold air spilling southward may result in high winds associated with gap wind events across many southern portions of the state on the 19th through 22nd that could gust in excess of 80-100 mph. As the cold air builds across the interior of the state, much below-normal temperatures are possible from the 21st through 23rd with daily minimum temperature anomalies in excess of -20 degrees F.

For Saturday March 24 - Friday March 30: The forecast 500-hPa circulation for Week-2 features anomalous ridging over the North Pacific, coupled with anomalous troughing initially over the Pacific Northwest and off the eastern seaboard straddling an anomalous ridge over the Southern Plains. Over the course of Week-2, the anomalous ridge over the Southern Plains is forecast to shift towards the Southeast, with heights falling across the Rockies as some degree of troughing shifts eastward. The ECMWF ensemble is more amplified with this trough relative to the GEFS, while the GEPS is similar in amplitude but less progressive and maintains the feature over the West throughout Week-2. The GEFS and Canadian ensembles are more amplified with ridging in the South during Week-2, whereas the ECMWF ensembles approach climatological height values by the second half of Week-2. Given the general shift from a higher amplitude pattern and greater consensus among model guidance during the first half of Week-2, all currently anticipated hazards during this period are forecast in the early part of the week as confidence wanes substantially beyond day 10.

Anomalously cold weather is forecast to linger from Week-1 into the early part of Week-2 across eastern mainland Alaska. The GEFS forecasts ensemble mean temperature anomalies of -20 degrees F or greater on the 24th, suggesting a moderate risk being warranted. The GEFS reforecast guidance also suggests a better than 40% chance of this region being below the 15th climatological percentile of minimum temperature on the 24th, and better than 20% chance of being in this bottom portion of the daily low temperature distribution on the 24th and 25th, leading to a slight risk of much below-normal temperatures. Beyond this period signals wane both in terms of the forecast anomalies and reforecast guidance values relative to climatology.

With the anomalous ridge initially forecast across the Southern Plains in Week-2, the potential for much above-normal temperatures exists. A small area along the Rio Grande has a slight risk of much above-normal temperatures on the 24th and 25th with the GEFS giving a 20-40% chance of daily highs exceeding 90 degrees F while also being in the 85th percentile or higher relative to climatology. ECMWF reforecast guidance is similarly warm across the region early in Week-2.

With anomalous troughing favored on either side of the aforementioned ridge early in Week-2, cold is possible across both the West and Northeast. A slight risk of much below-normal temperatures exists for the 24th and 25th across much of the West, with the exception of lower elevations across California and the Southwest, and for the Mid-Atlantic and Northeast. Each of these regions has a better than 20% chance of seeing subfreezing temperatures and for daily low temperature values to be below the 15th climatological percentile, per the GEFS reforecast guidance.

Lastly, a slight risk of heavy precipitation exists for portions of the Middle and Lower Mississippi Valley through the the Tennessee and Ohio Valleys on the 24th through 26th. Both the GEFS and ECMWF reforecast guidance gives a better than 20% chance of these regions seeing an inch of rain over the three day period and being above the 85th climatological percentile for the full period. The enhanced odds for rainfall appear tied to ample flow of moisture out of the western Gulf of Mexico into the highlighted region interacting with shortwave energy across the region that may help trigger convection.

The U.S. Drought Monitor, valid on March 13, 2018 indicates an increase in the coverage of severe to exceptional drought (D2-D4) from 15.50% last week to 16.30% this week. Severe drought continues to expand across the southern high Plains and moderate drought areas have expanded in Georgia.

Forecaster: CPC Forecaster


Click here to see a display of the GFS Ensemble Forecasts

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