Valid Saturday May 07, 2016 to Wednesday May 18, 2016
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT May 04 2016Synopsis
: 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.
Detailed Summary For
Saturday May 07 - Wednesday May 11:
- Severe weather across portions of the Central
Plains and the Southern Plains, Sat, May 7.
- Severe weather across portions of the Central Plains and the Southern
Plains, Sun, May 8.
- Heavy precipitation across portions of the Central Great Basin and
California, Sat-Sun, May 7.
- Heavy precipitation across portions of the Central Rockies, Sat, May 7.
- Heavy rain across portions of the Central Plains, the Middle Mississippi
Valley, the Lower Mississippi Valley, the Southern Plains, and the Upper
Mississippi Valley, Mon-Tue, May 9-10.
- Flooding possible across portions of Washington State, Sat-Sun, May 7-8.
- Flooding possible across portions of the Central Rockies, Sat-Sun, May 7-8.
- Flooding occurring or imminent across portions of the Central Plains, the
Lower Mississippi Valley, the Northern Plains, the Middle Mississippi Valley,
the Upper Mississippi Valley, and the Southern Plains, Sat-Sun, May 7-8.
- High winds across portions of the Southern Plains, Sat, May 7.
- Much above normal temperatures across portions of the Pacific Northwest,
the Northern Rockies, and the Northern Great Basin, Sat, May 7.
- Much above normal temperatures across portions of the Northern Plains, the
Northern Rockies, and the Northern Great Basin, Sun, May 8.
- Enhanced wildfire risk across portions of the the Southern Rockies and the
Southern Plains, Sat-Sun, May 7-8.
- Slight risk of much above-normal temperatures for portions of New England,
Thu, May 12.
- Slight risk of much above-normal temperatures for Northern California, the
Central Great Basin, the Pacific Northwest, the Northern Rockies, and the
Northern Great Basin, Thu-Sat, May 12-May 14.
- Severe Drought across the Central Great Basin, the Northern Plains, Hawaii,
the Northern Great Basin, California, Puerto Rico, the Southern Plains, and the
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
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
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.
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.