Valid Monday April 27, 2015 to Friday May 08, 2015
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT April 24 2015Synopsis
: A strong area of upper-level low
pressure is expected to develop over the east-central U.S. with a surface low
progressing from the southern Great Plains to the Gulf Coast on Monday and
Tuesday. Later in the week, a low pressure system may develop near the
mid-Atlantic coast. An area of upper-level high pressure is forecast to build
across the Rockies and high Plains by the end of April, while onshore flow
returns to the Pacific Northwest. A surface low is expected to weaken over the
eastern Gulf of Alaska early in the period. Hazards
Detailed Summary For Monday April 27
- Friday May 01:
- Heavy snow for parts of the mountains of southern Colorado, Mon, Apr
- Severe weather for parts Louisiana and Texas, Mon, Apr 27.
- Heavy rain shifting east from the southern Great Plains to the lower
Mississippi Valley, Gulf Coast, and Florida, Mon-Tue, Apr 27-28.
- Flooding occurring or imminent along the Choctawhatchee River in the
Florida Panhandle along with parts of southeast Texas.
- Flooding occurring or imminent for parts of the Souris River in North
Dakota due to water release from Lake Darling.
- A slight risk of much above-normal temperatures for parts of the central
and southern Great Plains, Sat-Sun, May 2-3.
- Severe drought for the central and southern Great Plains, Southwest, Great
Basin, California, the Pacific Northwest, southern Florida, and Hawaii.
A vigorous upper-level trough is forecast to eject from
the Four Corners region by Monday. Heavy snow is expected to continue into
Monday morning with snow levels potentially falling to around 6,500 feet for
the mountains of southern Colorado. Total snowfall amounts with this spring
storm are likely to range from 1 to 2 feet, locally higher, across the southern
On Monday, the shortwave trough ejecting east along with sufficient shear
and instability is expected to result in the risk of severe thunderstorms
across central/southeast Texas and southern Louisiana. Beyond Monday, the
surface front is forecast to shift south into the northern Gulf of Mexico and
decrease chances for severe weather.
Early next week, 500-hpa height falls, a nearly stationary front, and
abundant moisture from the Gulf of Mexico favor heavy rainfall from the
southern Great Plains southeast to the lower Mississippi Valley, Gulf Coast,
and Florida. The high-resolution model runs are consistent with a broad 1 to 3
inches (locally more) across these areas on April 27 and 28.
Although unseasonably cool temperatures are expected across the southern
Great Plains and Southeast from Monday through Wednesday, minimum temperatures
are forecast to average at or slightly below-normal. By Friday, building
500-hpa heights are expected to result in a significant warming trend across
much of the west-central U.S.
Model guidance continues to indicate the potential for a strong low
pressure system affecting the mid-Atlantic and Northeast on April 30 and May 1.
The primary hazards associated with this potential storm include heavy rain,
high winds, and coastal flooding. However, large model spread and poor
continuity precludes designation of any specific hazards along the East Coast
at this time.
Moderate flooding along the Choctawhatchee River in the Florida Panhandle
is expected to persist through at least Monday. Heavy rainfall during the next
week could prolong or trigger additional river flooding along the Gulf Coast.
No hazards are expected across Alaska as a surface low weakens across the
eastern Gulf of Alaska by Monday. For Saturday May 02 - Friday May
The 0Z GFS and 0Z ECMWF ensemble means on April 24 indicate a
progressive flow pattern with a trough shifting offshore of the East Coast, a
ridge centered over the Mississippi Valley, and a trough moving onshore to the
West Coast. A drier pattern is expected across the Southeast during the first
week of May. Late in Week-2, severe weather may return to the central and
southern Great Plains after the east Pacific trough moves inland into the
The increase in 500-hpa heights and downslope flow result in a slight risk
of much above-normal temperatures across parts of the central and southern
Great Plains on May 2 and 3. This is consistent with guidance from the GEFS
reforecast tool and the high-resolution 0Z ECMWF model on April 24 indicating
850-hpa temperatures warming above 21 degrees C across southwest Kansas and the
The most recent U.S. Drought Monitor, valid on April 21, indicates a very
slight decrease (from 19.14 to 18.97) in the percentage of the CONUS in severe
to exceptional drought (D2-D4).
Forecaster: Brad Pugh
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.