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FXUS21 KWNC 051804

PMDTHR

US Hazards Outlook

NWS Climate Prediction Center College Park MD

300 PM EDT April 05 2024



SYNOPSIS: Late next week, a surface low pressure system is forecast to bring 

enhanced precipitation amounts and episodes of high winds over the eastern 

contiguous U.S. (CONUS). The heavy precipitation threat is favored to time off 

before the start of week-2, however strengthening pressure gradients in the 

wake of the system support an increased risk of high winds for much of the 

northeastern CONUS. Later in week-2, developing mid-level low pressure over the 

eastern Pacific and an associated increase in onshore flow looks to bring 

above-normal precipitation over parts of the West Coast, though the risk of 

heavy precipitation remains low at this time. 



HAZARDS



Slight risk of high winds for portions of the Central Appalachians, 

Mid-Atlantic, Ohio Valley, Great Lakes, and Northeast, Sat, Apr 13.



DETAILED SUMMARY



FOR MONDAY APRIL 08 - FRIDAY APRIL 12: 

https://www.wpc.ncep.noaa.gov/threats/threats.php



FOR SATURDAY APRIL 13 - FRIDAY APRIL 19: Following the passage of a shortwave 

trough lifting out over the northeastern CONUS to bring potentially heavy 

precipitation over parts of the eastern U.S. late next week, there continues to 

be good agreement in the dynamical models favoring the development of positive 

500-hPa height departures overspreading much of the central and eastern CONUS. 

With anomalous mid-level ridging also predominantly featured upstream across 

the West through the middle of week-2, the overall mean height pattern looks to 

keep hazard potential at bay, and promote unseasonably warm (and rather 

pleasant) springtime temperatures for much of the lower 48. The height pattern 

is also expected to promote increasingly drier conditions for much of the 

country, though the two possible exceptions for disturbed weather are over the 

southern tier and the West Coast where near to above-normal precipitation is 

favored in the model guidance during the period.  







Tied to the aforementioned troughing late next week, models are in good 

agreement in regards to the strength and position of the accompanying mean 

surface low pressure system over the Canadian Maritimes. The highest 

precipitation amounts remain favored to occur well offshore, however the 

potential exists for strengthening pressure gradients over the northeastern 

CONUS with surface high pressure building behind the system. A slight risk of 

high wind remains issued for day 8 (Apr 13) based on continued support in the 

ECMWF Probabilistic Extremes Tool (PET) indicating increased chances (20-30%) 

for wind speeds exceeding the 85th percentile in the highlighted region.  







Within the highlighted region, it is worth noting that a major springtime 

snowstorm just brought upwards of a foot of snow over many parts of New 

England, with additional snowfall forecast in the region within the next day or 

so. In the wake of this system, building mid-level heights and southerly flow 

are favored, and the unseasonably warm spring temperatures and periods of 

rainfall during week-1 could accelerate snowmelt. No corresponding flooding 

hazard is issued given near to below normal precipitation favored during 

week-2, though any additional rainfall may exacerbate runoff may bring flooding 

along small streams, particularly for areas where the highest snowfall amounts 

were recently received. 







During the first several days of week-2, ensembles depict a weakness in the 

height field over northern Mexico underneath much of the anomalous ridging 

concentrated to the north.  Compared to the GEFS and Canadian, the ECMWF 

ensemble is more pronounced with this feature, depicting more cyclonic flow and 

higher precipitation amounts over parts of the Southern Plains and Lower 

Mississippi Valley on days 9 to 11 (Apr 14-16).  Likewise, an increased 

potential for heavy precipitation is shown in the ECMWF PET, with 20-30% 

chances for 3-day amounts exceeding the 85th percentile and 1 inch during the 

middle of the period. However, both the raw and calibrated guidance from the 

GEFS and Canadian are more unsupportive of this risk, and given the lack of a 

distinguishable mean surface low analyzed in the daily surface pressure fields, 

and more zonal surface flow from the Gulf of Mexico, no corresponding 

precipitation hazard is posted. 







From the middle of April and onward, much of the anomalous ridging over the 

Interior West and Great Plains is generally favored to shift eastward with 

time, allowing for more troughing to develop over the eastern Pacific and 

eventually encroach the West Coast. The associated increase in onshore flow is 

reflected in the raw precipitation tools as well as the GEFS and ECWMF PETs 

with increasing chances for 3-day amounts exceeding the 85th percentile over 

parts of the Pacific Northwest and the northern half of California.  Despite 

good model agreement even at this lead, no corresponding precipitation hazards 

are issued as actual daily amounts are unlikely to reach hazard criteria. 







No hazards are issued over Alaska. Near to above normal precipitation is 

favored across the southern Mainland and Southeast, and this is not anticipated 

to adversely affect the upcoming river break-up season.  



FORECASTER: Nick Novella 



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