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HOME> Expert Assessments>Hazards Outlook

U.S. Hazards Outlook - Made May 04, 2016

 Days 3-7Days 8-14Prob. Days 8-14
Precipitation No HazardsNot Available
TemperatureNo Hazards
SoilsNot Available

Categorical OutlooksDay 3-7Day 8-14
8-14 Day Probabilistic OutlooksTemperature HazardsPrecipitation Hazards

Valid Saturday May 07, 2016 to Wednesday May 18, 2016

US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT May 04 2016

Synopsis: In week-1 a surface low pressure system is expected to bring an array of regional hazards from severe weather and heavy rainfall to high elevation snowfall for the western and central CONUS. In the wake of this system enhanced fire weather risk is anticipated exist across parts of the southwest. As the system moves out, a more benign weather pattern sets up for week-2 with trends towards general high pressure across the west and low pressure across the east. Throughout the forecast period Alaska is anticipated to be impacted by a series of cyclones with associated impacts during week-1 before mid-level high pressure builds in week-2.

Hazards Detailed Summary

For Saturday May 07 - Wednesday May 11: The initial 500-hPa flow pattern in week-1 is expected to consist of high amplitude flow featuring an omega block across the CONUS highlighted by closed lows across the Southwest and Mid-Atlantic that flank a ridge through the Southern and Central Plains. Over the course of the week the pattern is anticipated to deamplify, particularly over the central and eastern CONUS as the ridge flattens out and the low transitions to an open wave respectively. The disturbance initially over the western CONUS is expected to be the key hazards influence on week-1 as it progresses slowly eastward and opens up late in the forecast period.

Initial hazards associated with the cyclone across the western CONUS are expected to be heavy precipitation (excess of 1 inch of liquid equivalency in 24 hours) across the Sierra Nevadas and Central Rockies on Saturday, May 7. This precipitation will fall as rain for both regions except for higher elevations where snow potential exists. The heavy precipitation across the Central Rockies possibly will introduce localized flooding concerns for the region on Saturday, May 7 and Sunday, May 8. The SPC has introduced a 15% severe weather risk on Saturday, May 7 area from the Central Plains southward through West Texas associated with potential supercell development along a dry line bringing primarily a large hail threat. High winds in excess of 35 mph are also anticipated in the vicinity of the Stockton and Edwards Plateaus of Texas on Saturday, May 7 associated with the low-level jet acting to fuel the severe weather. SPC anticipates the 15% severe weather threat to shift eastward on Sunday, May 8 stretching from South-Central Nebraska through Central Texas, once more associated with a dry line setting up across this region. Heavy rainfall is forecast across the Middle and Lower Mississippi Valleys back through East Texas for both Monday and Tuesday, May 9 and 10 as the cyclone continues eastward. This rainfall across East Texas and the Lower Mississippi Valley may exacerbate ongoing flooding occurring for this region. Hazard impacts from this low-pressure system are thereafter expected to wane as the system lifts northward towards Canada.

Behind the dry line associated with the aforementioned cyclone, enhanced fire weather conditions are expected across much of the southwest for Days 3 and 4. SPC indicates a specific risk area of southeastern New Mexico on Saturday and Sunday May 7 and 8 where warm and dry conditions are expected in conjunction with high winds (that are not expected to meet hazardous criteria). Outside of this specific area of elevated fire weather risk, conditions may approach hazardous criteria throughout Central and Southern New Mexico into West Texas Sunday, May 7 through Monday, May 9. Anomalous warmth is also expected north of the cyclone over the Western CONUS early in week-1. Areas that may see much above normal temperatures for Saturday include the Pacific Northwest on Saturday, May 7 where maximum temperatures may exceed climatology in excess of 16 degrees Fahrenheit. Melting snowfall with this warmth could possibly lead to farming for parts of north Central Washington on Saturday, May 7 and Sunday, May 8. This region of anomalous warmth is expected to shift eastward across Eastern Washington, Northern Idaho, and Northwestern Montana on Sunday, May 8.

A series of cyclones are anticipated to impact Alaska throughout week-1, yet no specific hazards are depicted at this time for Alaska. However, significant wave heights may approach 20 feet for the western Aleutians on Tuesday, May 10 associated with the most vigorous cyclone to impact the state during this week.

For Thursday May 12 - Wednesday May 18: Early in week-2 the forecast flow pattern is for predominantly zonal flow to dominate, with weak ridging favored across the western CONUS and troughing through the Great Lakes. Throughout the course of the week the pattern is anticipated to amplify somewhat, albeit not the the extent seen in week-1, with the ridge and trough propagating eastward. A 500-hPa trough is expected to come ashore over the western CONUS late in week-2. A mid-level ridge is forecast to amplify over Alaska during the early portion of week-2.

Precipitation hazards were considered for both the trough forecast across the Great Lakes around Saturday, May 14 and trough across the west late in week-2. Lack of consensus among dynamical guidance led to the lack of a specific hazard being depicted for either region, but will be revisited in the coming days.

Two regions have been highlighted for a slight risk of much above normal temperatures during the week-2 period. The first is for coastal New England on Monday, May 12 where the GEFS reforecast tool depicts probabilities of exceeding the climatological 85th percentile of maximum temperature exceed 30%. Also highlighted for a slight risk of much above normal temperatures is much of the Pacific Northwest for Thursday, May 12 through Saturday, May 14 associated with the ridge building across the west that could push lower elevation temperatures to exceed 85 Fahrenheit. A slight risk region of much above normal temperatures was considered for central Alaska during the first half of week-2 where a strong ridge is expected to develop and guidance suggests maximum temperatures could approach record values. Given that record high temperatures are generally at or below 80 Fahrenheit for this region a limited impact to life and property would be anticipated, and thus no hazard is shown on the map. Alaska will need to be monitored for any developing fire weather or snow melt related flood risks associated with this potential warmth in early week-2.

According to the U.S. Drought Monitor valid on April 26, severe, or greater intensity, drought covers 5 percent of the U.S. Drought Monitor areas with a continued decrease in coverage during the past six months.

Forecaster: Daniel Harnos

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