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FXUS21 KWNC 041803

PMDTHR

US Hazards Outlook

NWS Climate Prediction Center College Park MD

300 PM EDT April 04 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). While a heavy precipitation threat is favored to 

diminish by the start of week-2, strengthening pressure gradients in the wake 

of the system sustains the risk of high winds for much of the northeastern 

CONUS. The return of enhanced onshore flow is possible over parts of the 

western CONUS tied to an area of developing mid-level low pressure over the 

eastern Pacific by mid-April, however, substantial model disagreement precludes 

any corresponding hazards in the outlook.   



HAZARDS



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

Mid-Atlantic, Ohio Valley, Great Lakes, and Northeast, Fri-Sat, Apr 12-13.



DETAILED SUMMARY



FOR SUNDAY APRIL 07 - THURSDAY APRIL 11: 

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



FOR FRIDAY APRIL 12 - THURSDAY APRIL 18: Late next week, dynamical models 

continue to feature shortwave 500-hPa troughing lifting out over the 

northeastern CONUS, with anomalously positive mid-level heights overspreading 

much of the central and western CONUS upstream into the weekend. Later in 

week-2, a key difference between the ensemble guidance concerns the evolution 

of the anomalous ridging favored upstream. The 0z ECMWF favors a stronger ridge 

extending into the northeastern Pacific, whereas the 0z GEFS is more zonally 

narrow with this mid-level mean feature, while also favoring more troughing 

over the eastern Pacific. These differences over western North America 

significantly reduce outlook certainty, and absent any substantial troughing or 

cyclonic features in the mean 500-hPa height or surface fields, there appears 

to be little in the way of hazard potential, with unseasonably warm and drier 

than normal conditions for much of the CONUS during the outlook period. 







Tied to the aforementioned troughing over the northeastern CONUS, there is fair 

agreement between the GEFS and ECMWF ensembles depicting the mean surface low 

positioned over eastern Canada by the outset of week-2.  The uncalibrated GEFS 

and ECMWF generally show the highest mean precipitation amounts offshore, and 

given the overall weaker presentation of heavy precipitation signals in the 

Probabilistic Extreme Tools (PETs), a slight risk of heavy precipitation is 

removed in the updated outlook. However, a slight risk of high winds remains 

issued (Apr 12-13), and still includes parts of the Great Lakes and eastern 

Seaboard where guidance continues to favor potentially strong pressure 

gradients with support from the ECMWF PET depicting 20-30% for wind speeds 

exceeding the 85th percentile. 







In the near-term, a fairly potent low pressure system is tracking over the 

Northeast and is likely to bring mixed precipitation and heavy snowfall 

accumulations (locally upwards of 1 foot) over New England within the next day 

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

flow are favored, where the return of unseasonably warmer than normal 

temperatures and increased precipitation amounts during week-1 may accelerate 

snowmelt. The increased runoff may bring flooding along small streams, 

particularly for areas where the highest snowfall is received. No associated 

hazards are posted at this time, but this flooding potential will be monitored 

in upcoming outlooks. 







As anomalous mid-level ridging is favored to overspread the central and eastern 

CONUS through the middle of week-2, the GEFS favors mid-level troughing 

shifting eastward from the eastern Pacific, with increased onshore flow over 

the West Coast. The pattern evolution is at odds with ECMWF, which maintains 

fairly amplified ridging and a comparably drier pattern across much of western 

North America by mid-April.  Even with increased precipitation signals evident 

in the raw and calibrated GEFS PET, these amounts are not expected to reach 

hazard thresholds, and no precipitation related hazards are issued.  







No hazards are issued over Alaska. Near to below normal temperatures and 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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