KPITSnow Posted August 31, 2021 Share Posted August 31, 2021 2 minutes ago, TimB84 said: I tend to agree. Not necessarily because I think we’ll see a half foot of rain in the immediate Pittsburgh area - that’s probably an outlier, but because there’s a solid chance that some location in the PBZ forecast area (MGW, perhaps?) will see 6”. And that possibility covers a solid number of counties under their jurisdiction. Yep, and I think it depends on who is writing it. There was one a day or two that was excellent, but this dude who wrote this just is straight awful and frankly lazy. Here is the detailed one. Quote Tuesday Night and Wednesday... here comes Ida. The weakening tropical system Ida will begin to move northward across the TN Valley Tuesday night and accelerate in response to a northern stream trough digging southeastward from the Midwest. Rain from the northern side of Ida will overspread northern West Virginia and SW PA (and perhaps barely into SE Ohio close to the Ohio River) overnight and continue through much of Wednesday as Ida moves northeastward through Appalachia. This will pose a significant flood threat to locations south and east of Pittsburgh and anyone in that area needs to remain weather aware for the next few days. How much rain and where exactly? That`s the biggest question. Recent model guidance has trended slightly farther SE, painting the axis of heaviest rainfall somewhere between SW PA and the higher terrain of WV, with Morgantown being near the center axis in several models. Across the heaviest rainband, look for amounts between 3 and 6 inches with localized higher amounts. Farther north, amounts should drop off precipitously w/ areas north of Pittsburgh likely receiving less than an inch. Where does this put the immediate Pittsburgh metro? In an area of high uncertainty. Model guidance ranges from roughly just 1 inch upwards to about 5 inches for Allegheny County and surrounding area, all dependent on the exact track of the system. We should be able to hone in on these details by the evening suite of model guidance. Rain will come to an end by dusk or shortly thereafter on Wednesday as the remnants of Ida depart eastward, with much cooler, drier air filtering in behind the system. Link to comment Share on other sites More sharing options...
TimB Posted August 31, 2021 Share Posted August 31, 2021 12z HRRR (those darker yellows are still a little too close for comfort): Link to comment Share on other sites More sharing options...
Ahoff Posted August 31, 2021 Author Share Posted August 31, 2021 1 hour ago, KPITSnow said: This has some REALLY ugly potential. I would all be for a shift south as I don't really want to see 6 inches of rain over the metro. Perfect placement for a winter storm though. Too bad it's not January. Link to comment Share on other sites More sharing options...
Rd9108 Posted August 31, 2021 Share Posted August 31, 2021 32 minutes ago, TimB84 said: 12z HRRR (those darker yellows are still a little too close for comfort): I mean how accurate are models this far out to the point where 50 miles could be the difference between 1inch and 6inches. We've seen this before in winter. Link to comment Share on other sites More sharing options...
TimB Posted August 31, 2021 Share Posted August 31, 2021 1 minute ago, Rd9108 said: I mean how accurate are models this far out to the point where 50 miles could be the difference between 1inch and 6inches. We've seen this before in winter. Exactly. We’re far from out of the woods here. Link to comment Share on other sites More sharing options...
Rd9108 Posted August 31, 2021 Share Posted August 31, 2021 So the models are all over the place. kind of reminds me of a snow storm. Only difference is I'm rooting for the lowest number. unfortunately the opposite usually happens. Link to comment Share on other sites More sharing options...
Ahoff Posted August 31, 2021 Author Share Posted August 31, 2021 The insanity of the fact that in a few months we would be rooting for a northern trend. Here we just want to suppress. Link to comment Share on other sites More sharing options...
TimB Posted August 31, 2021 Share Posted August 31, 2021 Feel like the 12z models are shifting back south (GFS is an exception, but are we relying on the GFS inside 24 hours?). Link to comment Share on other sites More sharing options...
Rd9108 Posted August 31, 2021 Share Posted August 31, 2021 HRRR has been consistently on the northern end of the envelope This may come down to nowcasting Link to comment Share on other sites More sharing options...
Rd9108 Posted August 31, 2021 Share Posted August 31, 2021 Also UK bumped north of the 0z Link to comment Share on other sites More sharing options...
TimB Posted August 31, 2021 Share Posted August 31, 2021 The short range models gave me hope of a slight south nudge, but the globals are coming in north. Link to comment Share on other sites More sharing options...
RitualOfTheTrout Posted August 31, 2021 Share Posted August 31, 2021 1 hour ago, TimB84 said: Feel like the 12z models are shifting back south (GFS is an exception, but are we relying on the GFS inside 24 hours?). I was thinking the opposite after reviewing 12z models, most seemed to have nudged a bit North. NWS put out a solid discussion pertaining the upcoming situation. .SYNOPSIS... The remnants of Hurricane Ida will bring heavy rainfall and potentially significant flood impacts to the Upper Ohio Valley tonight into Wednesday. Cooler, drier air is expected after the system passes Wednesday night. && .NEAR TERM /THROUGH WEDNESDAY/... Regional radar imagery shows a line of showers developing and strengthening in area of modest CAPE (~500 J/kg) and along/near a diffuse frontal boundary stretching along and just north of I-70. With rainfall rates of up to 2 inches per hour possible, any training segments will pose a flash flood risk. Total amounts in the highest areas will likely be in the vicinity of 2 inches per HREF probabilities, effectively saturating the ground in those areas before tomorrow`s rainfall. This convection should wane towards dusk. Attention then turns to the remnants of Ida and a potentially significant flood event for the Upper Ohio Valley into the Allegheny Mountains. Ida is forecast to move into Appalachia Tuesday night before heading off the Mid-Atlantic coast on Wednesday. Very high moisture content associated with Ida will surge northward into the Upper Ohio Valley along a strengthening frontal/baroclinic zone that will lie right across the forecast area. Strong frontogenetical and isentropic lift in the frontal zone in the right entrance region of the northern stream jet will allow for a band of moderate-to-heavy rainfall to develop and persist across the area. Run-over-run model guidance has been consistent with placing the axis of heaviest rainfall in an area stretching from the Mon Valley to areas northeastward such as Uniontown and Connellsville and then into the Laurel Highlands. 24- hour totals ending 8PM Wednesday look to be around or possibly in excess of 6 inches in this heaviest axis, with rainfall totals dropping off fairly precipitously to north and west. The greatest uncertainty in the rainfall forecast will be across the rainfall gradient , which will encompass the immediate Pittsburgh metro area. HREF probabilities suggest rainfall amounts may be upwards of 4 inches towards the southern portion of Allegheny County, dropping significantly to perhaps just around 1 inch towards the Beaver County border. No changes are currently planned for the flash flood watch. Officially the watch begins at 2am, though rain is expected to begin before that. Wouldn`t rule out a warning or two today with afternoon convection or this evening as the initiate wave of Ida rainfall approaches the area. As far as impacts, we`re anticipating a somewhat similar scenario to significant tropical systems of the past such as Gordon (2018) or even Francis/Ivan (2014). The similarities exist within rainfall totals and duration, though the axis of heaviest rainfall will likely be slightly farther southeast than it occurred with Francis or Ivan. This will cause significant rises in the Monongahela River and its tributaries such as the Youghiogheny and Cheat Rivers. Additionally, flash flooding is likely in those surrounding areas with many smaller streams likely going to exceed bankful. If you live in a flood prone area, please have an emergency plan in place and methods for receiving warning information. Rainfall should begin to exit eastern Ohio and NW PA by noon Wednesday, eventually exiting the entire Pittsburgh forecast area by tomorrow evening once Ida shifts off and cool, drier air ensues. Link to comment Share on other sites More sharing options...
jwilson Posted August 31, 2021 Share Posted August 31, 2021 Not much consensus from the models. A pre-winter delight in storm tracking with Allegheny once again the battleground. Link to comment Share on other sites More sharing options...
TimB Posted August 31, 2021 Share Posted August 31, 2021 13 minutes ago, RitualOfTheTrout said: I was thinking the opposite after reviewing 12z models, most seemed to have nudged a bit North. NWS put out a solid discussion pertaining the upcoming situation. Yeah, early returns from the NAM and earlier runs of the HRRR looked promising for less rain. Everything else has made a decisive shift north. Actually, not sure where I got that. Maybe from the other convective models, or from haste. Wasn’t the NAM or HRRR. Other thing is these ongoing slow-moving storms this afternoon ahead of the main event. Flash flood warnings in effect this afternoon. Link to comment Share on other sites More sharing options...
RitualOfTheTrout Posted August 31, 2021 Share Posted August 31, 2021 8 minutes ago, TimB84 said: Yeah, early returns from the NAM and earlier runs of the HRRR looked promising for less rain. Everything else has made a decisive shift north. Other thing is these ongoing slow-moving storms this afternoon ahead of the main event. Flash flood warnings in effect this afternoon. Gotcha, yeah I didn't take into account the timing of your post vs the models I was looking at. The worst is still SE of Pittsburgh and although it seems like whatever the trend is in the last 12-18 hours continues until game time I don't see guidance being the far off but if there are any convective components to the rainfall that will through another variable into the mix. That line moving through now will saturate the ground before the main event for sure. I was hoping to have some clarity, my commute in takes me through various flood prone areas so it would have been nice to make the call on whether to just stay home tomorrow. Last thing I want is to get detoured or stuck on Washington Blvd. Link to comment Share on other sites More sharing options...
TimB Posted August 31, 2021 Share Posted August 31, 2021 Just now, RitualOfTheTrout said: Gotcha, yeah I didn't take into account the timing of your post vs the models I was looking at. The worst is still SE of Pittsburgh and although it seems like whatever the trend is in the last 12-18 hours continues until game time I don't see guidance being the far off but if there are any convective components to the rainfall that will through another variable into the mix. That line moving through now will saturate the ground before the main event for sure. I was hoping to have some clarity, my commute in takes me through various flood prone areas so it would have been nice to make the call on whether to just stay home tomorrow. Last thing I want is to get detoured or stuck on Washington Blvd. I edited the above post. I think it was the other convective models that wanted to push it south, as much as you can trust those. NAM and HRRR both had a slight increase in qpf in the immediate area. That’s the thing here, it’s just like winter. No clarity about anything. At least we know the p-type this time. Link to comment Share on other sites More sharing options...
Rd9108 Posted August 31, 2021 Share Posted August 31, 2021 7 minutes ago, RitualOfTheTrout said: Gotcha, yeah I didn't take into account the timing of your post vs the models I was looking at. The worst is still SE of Pittsburgh and although it seems like whatever the trend is in the last 12-18 hours continues until game time I don't see guidance being the far off but if there are any convective components to the rainfall that will through another variable into the mix. That line moving through now will saturate the ground before the main event for sure. I was hoping to have some clarity, my commute in takes me through various flood prone areas so it would have been nice to make the call on whether to just stay home tomorrow. Last thing I want is to get detoured or stuck on Washington Blvd. Flooding on the 10th street bypass already. It's starting early Link to comment Share on other sites More sharing options...
TimB Posted August 31, 2021 Share Posted August 31, 2021 12 minutes ago, Rd9108 said: Flooding on the 10th street bypass already. It's starting early Looks like some PWS in the east end are reporting 1.5”+ already. Dormont area too. Link to comment Share on other sites More sharing options...
KPITSnow Posted August 31, 2021 Share Posted August 31, 2021 Ummmm this is less than ideal that we are already seeing flooding issues with an outer band moving in. Link to comment Share on other sites More sharing options...
TimB Posted August 31, 2021 Share Posted August 31, 2021 To the surprise of absolutely no one, the Euro has shifted.....north. Also, 0.68” officially at PIT in a half hour. Link to comment Share on other sites More sharing options...
Rd9108 Posted August 31, 2021 Share Posted August 31, 2021 Less of the QPF amounts but this would cause some issues Link to comment Share on other sites More sharing options...
KPITSnow Posted August 31, 2021 Share Posted August 31, 2021 Driving on 910 and already a total you know what show. Link to comment Share on other sites More sharing options...
TimB Posted August 31, 2021 Share Posted August 31, 2021 18z HRRR looks ugly. 2” QPF and it’s only up to 9z. Link to comment Share on other sites More sharing options...
KPITSnow Posted August 31, 2021 Share Posted August 31, 2021 3 minutes ago, TimB84 said: 18z HRRR looks ugly. 2” QPF and it’s only up to 9z. Yeah..it’s going to make a run at 5-6 inches or more. It “jackpots” us Link to comment Share on other sites More sharing options...
TimB Posted August 31, 2021 Share Posted August 31, 2021 Just now, KPITSnow said: Yeah..it’s going to make a run at 5-6 inches or more. It “jackpots” us The key here is that unlike the 12z model suite, the 18z HRRR total doesn’t include what fell early this afternoon. Link to comment Share on other sites More sharing options...
Rd9108 Posted August 31, 2021 Share Posted August 31, 2021 3 minutes ago, TimB84 said: The key here is that unlike the 12z model suite, the 18z HRRR total doesn’t include what fell early this afternoon. Too bad this isn't winter 40 inches of snow would be crazy. 4-5 inches of rain not so much. 1 Link to comment Share on other sites More sharing options...
dj3 Posted August 31, 2021 Share Posted August 31, 2021 Hopefully atmospheric memory replays this in about 4 months 3 Link to comment Share on other sites More sharing options...
KPITSnow Posted August 31, 2021 Share Posted August 31, 2021 18z hrrr puts out 3-6 inches basically county wide. 1 Link to comment Share on other sites More sharing options...
KPITSnow Posted August 31, 2021 Share Posted August 31, 2021 This first band seems to be back building. Again not great. Link to comment Share on other sites More sharing options...
KPITSnow Posted August 31, 2021 Share Posted August 31, 2021 Yikes. 18z nam is horrific. The southern half of the county has a bunch of areas in the 6-8 inch range. Link to comment Share on other sites More sharing options...
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