FXUS21 KWNC 101815
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT April 10 2024

SYNOPSIS: Mid-level low pressure is forecast across the north-central CONUS 
early in week-2, with surface low pressure tracking into east-central Canada at 
the outset of the period. This set-up favors a frontal boundary extending from 
the Southern Plains and Lower Mississippi Valley through the Great Lakes and 
Interior Northeast. Increased moisture flow from the Gulf of Mexico favors the 
highest chances for heavy precipitation more over the southern areas, but a 
northward entrainment of moisture is likely along the front which may bring 
increased chances of heavy precipitation through parts of the Mid-Atlantic and 
Northeast. On the backside of the front, elevated chances for gusty winds are 
forecast over a broad area including the Southwest, Great Plains, and Great 
Lakes. Surface high pressure is forecast to build across the Northern Rockies, 
which should allow winds to diminish in that region, with a tighter gradient 
likely further south across the central Rockies and continued potential for 
upslope heavy snow.

HAZARDS

Moderate risk of heavy precipitation across portions of the Southern Plains and 
Lower and Middle Mississippi, Ohio and Tennessee Valleys, Thu-Sat, Apr 18-20.

Slight risk of heavy precipitation across portions of the Southern Plains, 
Lower and Middle Mississippi, Ohio, and Tennessee Valleys, Great Lakes, 
Mid-Atlantic, and the Interior Northeast, Thu-Sat, Apr 18-20.

Slight risk of heavy snow across portions of the Central Rockies, Thu-Fri, Apr 
18-19.

Slight risk of high winds across portions of the Southwest, Central and 
Southern Rockies, Great Plains, Upper and Middle Mississippi Valley, and Great 
Lakes, Thu-Fri, Apr 18-19.

Possible flooding across portions of northeastern Texas, extreme southeastern 
Oklahoma, and much of the Lower Mississippi Valley.

DETAILED SUMMARY

FOR SATURDAY APRIL 13 - WEDNESDAY APRIL 17: 
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY APRIL 18 - WEDNESDAY APRIL 24: At the end of week-1 and into the 
outset of week-2, the 0z GEFS, ECMWF, and Canadian ensembles are in good 
agreement regarding surface low pressure tracking into east-central Canada. 
Troughing is predicted across the north-central CONUS early in week-2, with 
amplified ridging and above-normal 500-hPa heights forecast along the Eastern 
Seaboard. This favors enhanced southerly flow along a slow-moving front 
forecast to be set-up over the east-central CONUS, which will lead to increased 
chances for heavy precipitation. Thunderstorm activity is also possible for 
areas farther south, which could lead to enhanced precipitation totals locally.



The GEFS and ECMWF Probabilistic Extremes Tools (PETs) depict at least a 20 
percent chance of 3-day precipitation totals exceeding the 85th climatological 
percentile and 1-inch over the Southern Plains and Middle and Lower 
Mississippi, Ohio, and Tennessee Valleys. The uncalibrated guidance is more 
robust, with the 0z ECMWF depicting some areas with a 20 percent chance of 
3-day precipitation exceeding 2-inches over these areas, with 24-hour totals 
possibly over 1-inch. Week-2 ensemble mean total precipitation exceeds 1.5 to 2 
inches in the 0z GEFS, ECMWF, and Canadian, with most precipitation forecast to 
fall early in the period. Given these increased signals, a moderate risk of 
heavy precipitation is highlighted across from the Ark-La-Tex region to the 
Ohio-Mississippi River Confluence, Apr 18-20. The slight risk extends farther 
north into the Ohio Valley and Interior Northeast given the enhanced 
frontogenetic forcing over these areas. A possible flood risk area is 
designated for parts of northeastern Texas, extreme southeastern Oklahoma, and 
much of the Lower Mississippi Valley due to antecedent wet conditions 
anticipated during week-1 and forecast heavy precipitation during week-2, where 
there are some locations already experiencing flood conditions. 



Elevated wind speeds are forecast behind this frontal system across a broad 
region extending from the Southwest, Great Plains, Mississippi Valley, and 
Great Lakes, with a slight risk for high winds posted for Apr 18-19. Across the 
Northern Tier, the departing surface low is predicted to lead to a tight 
pressure gradient across the region. While a moderate risk was considered given 
the set-up, the magnitude of wind speeds was not overly impressive in recent 
deterministic GFS and ECMWF runs. As the aforementioned front moves out by the 
middle of week-2, there are some indications that elevated wind speeds could 
work their way into the Northeast and this will be reevaluated tomorrow. 
Surface high pressure building southward out of Canada favors decreasing wind 
speeds across the Northern Rockies. However, a tight pressure gradient remains 
forecast across the Central and Southern Rockies and Plains. This may also lead 
to continued chances for upslope snow across the Central Rockies, with the 
uncalibrated 0z ECMWF and GEFS snow water equivalent (SWE) PET continuing to 
support a slight risk for heavy snow over the region Apr 18-19. Additionally, 
the National Interagency Fire Center (NIFC) indicates the greatest potential 
for wildfires for day-7 across much of the Four Corners and Southern Plains, 
and this should persist into week-2 given the continued potential for increased 
wind speeds and little precipitation.



A period of below-normal temperatures is possible across parts of the Great 
Basin, Rockies, and Northern Plains early in the period, with some sporadic 
areas of mixed vegetation susceptibility noted across parts of Utah and 
Colorado. Subfreezing temperatures are possible across these areas, but the 
threat of any widespread impacts is marginal, thus no related hazard is posted. 
By the middle of week-2, this anomalous cold may shift across parts of the 
eastern CONUS. However, temperatures are unlikely to reach hazards thresholds.



Across Alaska, the week-2 mean pattern is predicted to be dominated by positive 
500-hPa height anomalies across much of the state initially, with increasing 
northerly flow and troughing extending southward from the Arctic favoring 
increased chances for below-normal temperatures. Surface low formation is 
possible over the Gulf of Alaska during week-2, although this is not 
anticipated to support any hazards at this time.

FORECASTER: Thomas Collow 

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