Valid Thursday April 23, 2015 to Monday May 04, 2015
US Hazards Outlook
NWS Climate Prediction Center College Park MD
EDT April 20 2015Synopsis
: A strong area of upper-level low
pressure is expected to persist across southeast Canada during the next week,
while a couple of low pressure systems progress across the western U.S. Surface
high pressure is forecast to extend south from Canada into the Midwest from
Thursday through early next week. A broad area of low pressure is expected to
remain over the Gulf of Alaska. Hazards
Detailed Summary For
Thursday April 23 - Monday April 27:
- Severe weather
for parts of Louisiana, Oklahoma, and Texas, Thu, Apr 23.
- High winds for parts of the Southwest and southern Great Plains, Thu-Fri,
- Heavy rain and high-elevation snow for parts of the Pacific Northwest,
- Flooding likely for western Kentucky and southeast Texas.
- Flooding possible near the confluence of the Ohio and Wabash Rivers in
western Kentucky/southeastern Illinois.
- Flooding occurring or imminent for parts of the Souris River in North
Dakota due to water release from Lake Darling.
- Severe drought for the central and southern Great Plains, Southwest, Great
Basin, California, the Pacific Northwest, southern Alabama, southern Florida,
Cyclonic flow associated with the
anomalous upper-level trough centered over southeast Canada is likely to result
in below-normal temperatures across the Great Lakes and Northeast. Subfreezing
temperatures are forecast across the Upper Mississippi Valley, Great Lakes, and
parts of the Northeast, but these temperatures are not too anomalous (10
degrees F or less below-normal) for late April.
A shortwave trough is expected to progress across the Four Corners region
later this week and then weaken as it encounters confluent flow across the
eastern U.S. High-elevation snow (above 8-9,000 feet) is expected to accompany
the shortwave trough across the central Rockies. Since the shortwave trough is
expected to be progressive, a heavy snow hazard is not posted for this region.
High winds (gusts above 40 knots) are expected from the desert Southwest east
to the southern high Plains on Thursday and Friday. These gusty winds may
generate blowing dust across these areas.
On Thursday, severe weather is possible across southeast Oklahoma, the
eastern half of Texas, and western Louisiana ahead of the shortwave trough
ejecting from the Southwest. Moderate instability and strong deep-layer wind
shear are expected to favor the development of severe weather across this
region. Model divergence precludes designation of a severe weather hazard area
beyond Thursday at this time.
Onshore flow is expected to increase across the Pacific Northwest during
the weekend and increase the chances for heavy rain and high elevation snow
across the coastal ranges of Washington and northern Oregon. Since the high
resolution models indicate 2 to 6 inches of precipitation, liquid equivalent,
for these areas, a heavy precipitation hazard is posted for parts of the Oregon
and Washington. Snow levels are likely to fluctuate and residents are urged to
refer to the latest forecasts/statements from their local NWS offices.
Anomalous rainfall (more than 4 inches above-normal) during the past month
resulted in moderate river flooding across parts of Kentucky and southeast
Texas. These rivers are expected to remain in moderate flood stage through at
least Friday. Minor flooding is occurring along the lower Ohio River and may
reach moderate stage later this week.
No hazards are expected with the broad trough over the Gulf of Alaska with
the heaviest precipitation remaining south of the Alaska Panhandle and winds
likely below hazards criteria. For Tuesday April 28 - Monday
An upper-level trough is expected to persist across eastern North
America early in Week-2, while onshore flow continues to affect the western
U.S. This predicted longwave pattern is likely to maintain relatively cool
temperatures across the eastern U.S. at the end of April. Recent
high-resolution GFS model runs indicate the potential for a late frost or
freeze across the southern Appalachians and mid-Atlantic on April 28-29, but
the high-resolution 0Z ECMWF model is a warmer solution.
The most recent U.S. Drought Monitor, released yesterday, indicates a very
slight decrease (to 19.14 from 19.17) in the percentage of the CONUS in severe
to exceptional drought (D2-D4). This week's map is very similar to last week's,
with relatively minor adjustments made.
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.