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Sept 1st/2nd Hurricane Ida Remnants OBS:


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Welp, here we go.  SPC expanding that enhanced risk across most of the area. Looks like they just updated the outlook for the area late tonight. Even the DC area already under the gun for tornadoes.. They even have a tornado watch till 8am. 


Going to be a long and nerve racking day with this tornado threat.  I can't recall seeing a 10% for are area, which is pretty high.  Time for bed.  No doubt, we'll all be watching how things go tomorrow. Definitely be safe out there..

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The remnants of Ida will be affecting the region today and tonight,
with significant impacts expected for the area. Model trends early
this morning continued a slight northward nudge of the highest QPF
axis, with the GFS/NAM/ECMWF in good agreement that 3+ inches of
rainfall will occur near/northwest of the Fall Line (with embedded
totals 6+ inches somewhere in the southern Poconos and/or Lehigh
Valley and vicinity). The CMC remains farther south (almost to
outlier status), with the main axis generally between I-76 and I-80.
The convection-allowing models (CAMs) are in between, and these are
generally in line with our current thinking this morning.

There are a few reasons for favoring a slightly farther south
solution to the main QPF axis. For one thing, models tend to shunt
warm sectors too far northward in advance of these systems,
particularly ones that are in the process of intensifying via large-
scale baroclinic processes. Additionally, models tend to bias
convective precipitation too far north, in association with the
synoptic forcing, rather than with the ambient/pooling instability
(which tends to win out with convectively-enhanced events like
these). Finally, suspect upslope contributions to precipitation are
being underrepresented farther southeast near the Fall Line to the I-
95 corridor. For these reasons, our latest QPF forecast did not
adjust totals as far north as the consensus of the coarser NWP
models. However, these discrepancies do lead to higher uncertainty
with forecast totals along the I-95 corridor. For example,
Philadelphia may end up anywhere between 1 and 5 inches of rain
based on the array of guidance available.

However, the risk of flash flooding is not only tied to total
rainfall but also duration, and the CAM solutions would suggest that
much of the rainfall south of the high-QPF axis will be occurring in
a relatively short period of time. Excessive rainfall rates (via PWs
well north of 2 inches) are likely with the main convective show
late this afternoon into the early overnight hours, and will likely
lead to several instances of flash flooding near the urban corridor.
Therefore, despite somewhat lowered QPF for the I-95 corridor
southeastward, the risk of flash flooding remains quite elevated
because of the rainfall rates. The HREF guidance provides some
insight here, with the 00z ensembles indicating probabilities of 1-h
rainfall accumulations exceeding flash flood guidance (FFG) above 50
percent in virtually all areas northwest of I-95 in our CWA during
the evening hours, despite a range of 3-5 inches in total QPF.
Notably, the probabilities of 6-h rainfall accumulations exceeding
FFG are above 90 percent in much of the same area, which conveys the
seriousness of the flooding threat for our area quite well.

Of course, that is not all. With the warm sector expected to shift
northward into at least the southern half of the CWA, the ambient
preconvective environment will be quite favorable for severe
weather. Model soundings indicate MLCAPE 1000-2000 J/kg (closer to
500-1000 J/kg near the warm front), 0-6 km bulk shear nearing 40 kt,
and SRH > 200 J/kg in the late afternoon and early evening hours.
This is an environment supportive of rotating storms, with CAM
simulations suggesting a mixed mode of short line segments and
cellular storms. Damaging wind gusts and tornadoes are the main
threats, and the SPC has nudged the enhanced risk slightly farther
north given model trends this morning. Given the coverage of
convection expected, the favorable environment is quite concerning,
with the severe potential continuing to look more and more
impressive. The main time window for severe weather is likely in the
20z to 06z time frame from west to east. Individual cells will
likely move quickly north-northeast, but the overall system will
move only slowly eastward, so training convection poses a flash
flood risk in the southern half of the CWA.
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Models clearly struggling (not robust enough) already with the scope of the early morning rain and thunderstorms over NE MD, N. DE and SE PA. I believe this is the activity that rocked central VA overnight. HRDPS showed this scenario best at 0z. If we are to run with that model it paints a brutal picture later today for most of us. 




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19 minutes ago, irishbri74 said:

Terrible start to the day ..


I had the joy of driving from Pennsville, NJ to Newark DE.  I encountered heavy downpours from I95 to 896 to 279.  Wasn't expecting such a miserable drive to work today, thought it would only be going home. As usual, I was incorrect.



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26 minutes ago, irishbri74 said:

Awesome… radar outrages/info outtages? 


They are doing maintenance on Radarscope. Great timing huh? Use the Base modes from 5:30 AM CT - 6 AM CT. After that it should be back up and running on Super-res. 

Additional - Everything is down. Switch to NOAA for the data provider. 

Sorry for the bad info. 😬

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Nws reporting station 13 miles away from my location in Hanover  shows about .5" so far. But I  checked my old digs at Bwi and they had a thunderstorm between 4-5am that dropped 1.98"! Now that's some heavy rain.


Edit: Here's that storm on radar. Time sensitive. It was a quick mover to drop that much rain.


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Torrential rain and some thunder in West Deptford this morning. Thought I’d be ok leaving for work and wet coming home later. Looks like we should catch a break after these initial cells roll through. Then we wait to see what this afternoon/ evening brings with severe weather. 

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