Quantitative Precipitation Forecast Discussion NWS Weather Prediction Center College Park MD 515 PM EDT Sun Jun 03 2018 Final Day 1, Day 2 and Day 3 QPF Discussion Valid Jun 04/0000 UTC thru Jun 07/0000 UTC Reference AWIPS Graphics under...Precip Accum - 24hr For the 04/00z QPF issuance: no significant changes were made to the 03/18z QPF issuance. A few tweaks were made across the interior Mid Atlantic and Northeast based on radar trends, and across the Southwest based on radar trends and recent HRRR runs. ...Mid Atlantic/Northeast/Great Lakes/Ohio Valley... A meandering low over centered over eastern Virginia will continue to support areas of moderate to heavy precipitation across portions of the Mid Atlantic through the remainder of the afternoon into the evening hours. Deep saturation through the air column continues to support very efficient rain processes, with some areas continuing to see heavy amounts accumulate quickly. The heavy rainfall threat is still expected to diminish this evening as a upstream trough moving across the Great Lakes begins to drive the low offshore. This low is expected to move off of the Mid Atlantic coast overnight, with the models in generally good agreement taking the system south of New England on Mon. Strong southerly low level flow ahead of the low is expected to direct a plume of deep moisture into coastal southern New England on Mon, with the GFS showing PWs increasing to around 2 inches on Mon. This moisture interacting the with favorable upper dynamics ahead of an upstream low closing off over southeastern Canada, is expected to support some moderate to heavy rains across southeastern New England. Increasing instability and deepening moisture ahead of the aforementioned upper trough and its associated cold front should continue to support developing showers and thunderstorms across the Ohio valley into the central Appalachians this afternoon, with enhanced divergence ahead of the upper trough supporting a greater threat for heavy amounts across eastern Ohio into western Pennsylvania and West Virginia this afternoon. As the front pushes further east into a more stable airmass, rainfall rates are expected to diminish while the system moves across central to eastern Pennsylvania and New York overnight. However, the moisture and forcing ahead of the front may be sufficient enough to produce moderate to locally heavy amounts, especially across portions of Upstate New York. ...Southern Rockies/Plains... Southwesterly flow ahead of shortwave trough moving into the Four Corners region continues to moisten the mid levels across New Mexico and southern Colorado as southeasterly winds behind a cold front that has settled southwest into West Texas begin channel low level moisture into the region. This will continue to support developing storms across the mountains before spreading east into the High Plains this afternoon and evening. With PW anomalies increasing to 2-3 standard deviations above normal, there remains a good model signal for locally heavy accumulations this afternoon and evening from the southern Colorado and New Mexico ranges southeastward into the adjacent High Plains of eastern New Mexico and West Texas. Forecast confidence diminishes overnight as the hi-res models show significant spread with respect to how quickly convection diminishes as it moves further east into central Texas. While the NAM CONEST shows widespread moderate to locally heavy amounts spreading east into central Texas, the HWR-NMMB shows convection diminishing much sooner with only scattered light amounts. WPC QPF reflects a compromise similar to the HREF Mean, maintaining at least some light to moderate amounts along an axis of deeper moisture and greater instability across central Texas. As the aforementioned shortwave continues to move east, models continue to differ late in the period with possible convective redevelopment across central into southeast Texas, with the NAM CONEST this time being the much drier solution. With limited confidence, continued to follow the HREF Mean through the end of the period. Day 2 ...Northern New England... No significant changes made to the previous WPC qpf across northern to eastern portions of New England with the comma head/deformation precip region to the northwest of the surface low moving northeast from off the southeast New England coast to south of Nova Scotia. Aside from some minor timing differences---model consensus is for moderate precip totals over northern portions of New England and moderate to heavy over eastern portions of Maine. ...Upper MS Valley---Lower Great Lakes---Upper OH Valley---Central Appalachians into the Mid-Atlantic... In the wake of the low moving off the New England coast day 2--- a secondary cold front will drop southward through the Great Lakes and toward the Ohio Valley. Additional precipitation likely ahead of this front from the Upper MS Valley---across the lower Great Lakes and into the Upper OH Valley---Central Appalachians into the Mid-Atlantic. Generally light to moderate totals expected---with upslope into the Central Appalachians supporting locally heavy amounts here. Days 2 & 3 ...Northern Plains into the Upper MS Valley... Shortwave energy pushing east northeast into the Northern High Plains late day 2 will begin to strengthen the low level southerly inflow into the associated frontal boundary pushing into the Northern Plains. This will begin to initiate convection in the vicinity of this front late Tuesday afternoon---with this activity likely becoming well organized Tuesday night into early Wednesday as it pushes across portions of the Northern Plains and toward the Upper MS Valley. Heaviest totals likely during the day 3 time period with moderate to heavy amounts depicted across central to eastern ND---northern SD into much of MN and western WI. This activity likely will weaken after 1200 UTC Wednesday but may again re-fire late Wednesday afternoon. Convection expected to be fairly progressive with only a marginal risk depicted for the day 3 Excessive Rainfall Outlook...12Z Tue-12Z...Wed over central to eastern ND into northwest MN. ...Southern Plains toward the Lower MS Valley... Organized convection potential will continue day 2 along the frontal boundary lifting slowly northward across central TX. South to southwesterly low level flow into this front will support additional organized convection pushing southeast across southern OK/Northern TX Monday night into early Tue and toward the Lower MS Valley later Tuesday. Any remaining activity along this front day 3 expected to be confined to the Central Gulf coast/Lower MS Valley region with moderate to locally heavy totals possible. ...Central to South Florida... The eastern extent of the front over the Southern Plains will be very slow moving over Central Florida---focusing an axis of above average pw values along and to its south over Central to South Florida both day 2 and 3. This will support moderate to heavy precip totals along and south of this front days 2 and 3 for Central to South Florida. Pereira/Oravec Graphics available at www.wpc.ncep.noaa.gov/qpf/qpf2.shtml