AT2k Design BBS Message Area
Casually read the BBS message area using an easy to use interface. Messages are categorized exactly like they are on the BBS. You may post new messages or reply to existing messages! You are not logged in. Login here for full access privileges. |
Previous Message | Next Message | Back to General Weather-related Discussi... <-- <--- | Return to Home Page |
|
||||||
From | To | Subject | Date/Time | |||
![]() |
Mike Powell | All | HVYSNOW: Probabilistic He |
December 19, 2024 9:03 AM * |
||
FOUS11 KWBC 190856 QPFHSD Probabilistic Heavy Snow and Icing Discussion NWS Weather Prediction Center College Park MD 356 AM EST Thu Dec 19 2024 Valid 12Z Thu Dec 19 2024 - 12Z Sun Dec 22 2024 ...Midwest to Great Lakes... Days 1-2... A progressive Alberta Clipper producing a swath of heavy snow over North Dakota tonight will track across the Upper Midwest today. Modest 850mb WAA along the warm front and 850mb theta-e wrapping around the northern flank of the storm will prompt a snow to come down at 1-2"/hr rates in some cases from eastern ND to central Minnesota and central Wisconsin. The higher end of those rates will be harder to come by east of the Mississippi River as 850mb frontolysis sets in, leading to a reduction in snowfall rates. Still, the 500mb shortwave trough responsible for upper level ascent will still preside over the region and allow for periods of moderate-to-heavy snow through Thursday evening. In fact, some snowfall could be lake-enhanced along the shores of Wisconsin and Illinois as northerly winds advecting -10C 850mb temps race over Lake Michigan. By Thursday night, the 850mb low will track through northern Indiana with the best accumulating snow potential to the north of the 850mb low track. This favors central and northern Michigan Friday morning with a chance for the Detroit metro area to see light accumulations Friday afternoon. The storm system will gradually weaken into an open wave Friday afternoon as it approaches the central Appalachians, effectively ending the period of snowfall related to this Clipper in the Great Lakes by Friday evening. The WSSI shows a large swath of Minor Impacts that stretch from North Dakota and far northern South Dakota to as farther east as northern Michigan. There are some embedded Moderate Impact areas, primarily in parts of central North Dakota, around the Twin Cities metro, and in eastern Wisconsin. Moderate Impacts imply these areas can expect hazardous driving conditions with some potential closures and disruptions to infrastructure. WPC probabilities sport high chances (>70%) for snowfall totals >4" from central MN to the Door Peninsula of Wisconsin. It is worth noting that there are some localized low chance probabilities (10-30%) for snowfall totals >8" in central MN and central WI, as well as around the Green Bay area where lake-enhanced snowfall could result in localized amounts approaching 10 inches. ...Central Appalachians to Northeast.... Days 2-3... As the Alberta Clipper tracks through the Lower Great Lakes Friday morning, a secondary 500mb vort max that raced south from south- central Canada will begin to phase with the shortwave associated with the Clipper. This process, starting as early Thursday night, will lead to an amplification of the 500mb trough as it tracks towards the Central Appalachians Friday morning. Meanwhile, off the East Coast, increasing upper level divergence along a frontal boundary will allow for low pressure to quickly organize and strengthen Friday afternoon. As WAA increases along the front, moisture will wrap around the low and lead to broad precipitation shield just off the Northeast coast Friday night. This could result in heavy snow along Downeast Maine, but how close to the Maine coastline the storm gets remain lower in confidence. WPC probabilities suggest the eastern-most portion of Downeast Maine has low-to-moderate chances (30-50%) for snowfall >6" of snow through Saturday evening. In addition, high pressure over Quebec will work in tandem with the deepening storm system to tighten the pressure gradient and strengthening low-level northerly winds off the MA Capes. There is the potential for ocean-effect snow over southeast MA Friday evening. WPC probabilities show low chances (10-3) for snowfall >4", which does include the Boston metro area. Throughout the rest of the Northeast, western NY and northern PA will see the clipper's remnant 850mb circulation track overhead with modest 850-700mb moisture and weak 850mb WAA will supply the ingredients necessary for periods of snow late Thursday night and into Friday. By Friday afternoon, the forecast over parts of the northern Mid-Atlantic will hinge upon the strength of low-level easterly flow and a convergence axis over the region, while sufficient upper level divergence from the left-exit region of a 500mb jet streak arrives. Should these factors mesh together in just the right way, a pivoting band of snow may organize some where between northeast MD or the northern DelMarVa Peninsula on northeast through eastern PA, the Poconos, and into the Tri-State area. The latter is most favored for accumulating snowfall as WPC probabilities show moderate chances (40-60%) for snowfall totals surpassing 2" between Friday afternoon and early Saturday morning. If there is one mountain range that is favored to witness heavier snowfall, it is the central Appalachians in eastern WV and western MD. As the remnant surface low of the Clipper heads east Friday evening, its moisture source will track into the mountains at the same time as northwesterly winds begin to increase. The end result is upslope flow that causes periods of snow as far north as PA's Laurel Highlands. WPC probabilities favor those windward slopes of eastern WV with moderate chances (40-60%) for snowfall >4", especially at elevations above 2000ft between 18Z Fri - 18Z Sat. For all these areas mentioned in this section, the WSSI shows Minor Impacts for impacted areas that would primarily lead to locally hazardous travel conditions through Saturday morning. The probabilities for significant ice accumulations are less than 10 percent. Mullinax $$ --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (618:250/1) |
||||||
|
Previous Message | Next Message | Back to General Weather-related Discussi... <-- <--- | Return to Home Page |
![]() Execution Time: 0.018 seconds If you experience any problems with this website or need help, contact the webmaster. VADV-PHP Copyright © 2002-2025 Steve Winn, Aspect Technologies. All Rights Reserved. Virtual Advanced Copyright © 1995-1997 Roland De Graaf. |