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> July 21-22, 2018 MidAtl/NE Coastal Storm, Short Range Forecasts - Observations
Undertakerson
post Jul 20 2018, 09:04 AM
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While many are migrating, the weather moves along to an end of the recent "winning weather streak" for most of the region.

Once again, I picked the correct week for a vacation and, save for past Tuesday's rain (which did not last all day) - have had a delightful run or typical summer.

That looks to change as soon as tomorrow as a system that has some of the appearance of a winter time Nor'easter, approaches in response to the parent low in the Lakes region.

GFS seems to want to make more of this, and sooner, than do the other global set I've seen so far today - moving it into the MidAtl as early as tomorrow afternoon. Others delay the arrival, included in there is the NAM version.

Here's NAM QPF output, as the front that moves in the wake of the coastal, as it lifts northeast, gets stuck and become the focal point for rainy "mayhem" - potentially lasting the entire following 7 day time pd.


Attached Image


Here's the most recent WPC outlook for our time pd of interest.


Attached Image


This post has been edited by Undertakerson: Jul 21 2018, 08:26 AM
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psu1313
post Jul 20 2018, 09:14 AM
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QUOTE(Undertakerson @ Jul 20 2018, 10:04 AM) *
While many are migrating, the weather moves along to an end of the recent "winning weather streak" for most of the region.

Once again, I picked the correct week for a vacation and, save for past Tuesday's rain (which did not last all day) - have had a delightful run or typical summer.

That looks to change as soon as tomorrow as a system that has some of the appearance of a winter time Nor'easter, approaches in response to the parent low in the Lakes region.

GFS seems to want to make more of this, and sooner, than do the other global set I've seen so far today - moving it into the MidAtl as early as tomorrow afternoon. Others delay the arrival, included in there is the NAM version.

Here's NAM QPF output, as the front that moves in the wake of the coastal, as it lifts northeast, gets stuck and become the focal point for rainy "mayhem" - potentially lasting the entire following 7 day time pd.


Attached Image


Here's the most recent WPC outlook for our time pd of interest.


Attached Image


We have two threads open for this now. My concern is that this new pattern lingers into August.
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Undertakerson
post Jul 20 2018, 02:01 PM
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QUOTE(psu1313 @ Jul 20 2018, 10:14 AM) *
We have two threads open for this now. My concern is that this new pattern lingers into August.

The OFM signals suggest that as well. At least the BSR does - the way I see it, troughs dominate ridging.
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phils1
post Jul 20 2018, 02:08 PM
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*Significant coastal storm on Saturday/Saturday night begins a very wet pattern for the eastern US...this storm will head northward into interior New England by early Sunday and weaken, but this will not end the rainfall by any means. A flow of air from the tropical Atlantic to the Mid-Atlantic will persist from Sunday through next week and lead to numerous rounds of showers and thunderstorms in the eastern US*

https://www.perspectaweather.com/blog/2018/...-the-eastern-us
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KENNYP2339
post Jul 21 2018, 06:01 AM
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After observing this morning radar, I think the rain should be arriving earlier than anticipated, I think I was slated to have the rain show up between 8pm - 10pm time frame, since the rain is already at the Delmarva zone and moving briskly to the north I wouldn't be surprised to have showers by 3-4pm time frame.
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MaineJay
post Jul 21 2018, 07:03 AM
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Storm taking shape

Band 8
Attached Image

http://rammb-slider.cira.colostate.edu/?sa...;s=rammb-slider

PWATs

Attached Image


--------------------
The Perseids are coming, The predators are coming! Peaking ~August 12-13
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Undertakerson
post Jul 21 2018, 09:04 AM
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I like how the CTP AFD mentions blending "man and machine" smile.gif


QUOTE
We are keeping the forecast highly consistent and still expect


a 9-18 hour period of moderate and occasionally heavy rain with
embedded/elevated thunder. As the clouds continue to thicken
and lower this morning, the temps will stabilize, with little
movement expected through the daylight hours
. Thus, our early
morning temps could be the maxes, or at least within a deg or
two of the eventual maxes for the day.

Most model guidance is very certain that it will rain over our
eastern third to half. PoPs deserve to be 100pct. The 06Z NAM
has come back to the west and over Elk-Centre-Dauphin Cos. But,
this is a 06Z run, and skepticism still lives in my brain for a
solution which shifts so drastically in just 6hrs. But, at least
it is not as far west as the HREF mean QPF area. That looks much
too far to the west.

The rainfall will be falling onto ground which could some rain,
as the drought monitor is starting to show some color in our SE
counties. The heaviest of the rainfall in these SErly flow set
ups is usually in the SE-facing slopes of Schuylkill Co and
along Blue Mtn in Lebanon/Dauphin/Cumberland Cos. The upslope
can really push totals much higher than we think they could be.
Have kept an eye on the WPC ExRainOutlook and the newest Day1
outlook puts all of our SE and Schuylkill Co into the SLGT risk
area. With support from both man and machine, and careful
collaboration with the neighbors,
we have posted a flash flood
watch starting this aftn and ending around midnight for the area
highlighted. The main points against the flash flood risk are
the relatively quick forward movement of the coastal low and
assocd PWAT anomaly (+2 std devs), and the flash flood guidance
(FFG) which is very high (3-4"/6hrs) in all of Lancaster and
York Cos and the lower elevs of Dauphin and Lebanon Cos.

Most problems with this event should end up being nuisance
flooding. But 2" of water anytime of year can create minor,
local problems.
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LUCC
post Jul 21 2018, 09:14 AM
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Think we can get that ULL out west to phase with coastal sooner. Lmao

Rain has started here in extreme SNJ, Wildwood Crest.
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jacksonjeff
post Jul 21 2018, 09:54 AM
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QUOTE(LUCC @ Jul 21 2018, 10:14 AM) *
Think we can get that ULL out west to phase with coastal sooner. Lmao

Rain has started here in extreme SNJ, Wildwood Crest.

Lol
So no virga!!!!
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Undertakerson
post Jul 21 2018, 10:08 AM
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QUOTE(jacksonjeff @ Jul 21 2018, 10:54 AM) *
Lol
So no virga!!!!

lmao at you guys this morning. So well that spirit remains. smile.gif
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MaineJay
post Jul 21 2018, 10:16 AM
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SREFs are creeping down up here.

Attached Image


https://www.spc.noaa.gov/exper/sref/srefplumes/?SID=LEW

12z NAM with only about 1/4"-1/2" for the sebago lake region.

Attached Image


Attached Image

It's going to be a battle up here between how quick that trof swing the best forcing north, and how quick the ridging noses in.



https://www.tropicaltidbits.com/analysis/mo...072112&fh=1


--------------------
The Perseids are coming, The predators are coming! Peaking ~August 12-13
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yamvmax
post Jul 21 2018, 10:33 AM
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Beautiful fall like day here at the moment.
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jacksonjeff
post Jul 21 2018, 10:39 AM
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QUOTE(Undertakerson @ Jul 21 2018, 11:08 AM) *
lmao at you guys this morning. So well that spirit remains. smile.gif

Got to laught to keep from crying!!!
Taking the wifey to the city for the night for dinner and a show. I was hoping for 4 hours of virga.
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PoconoSnow
post Jul 21 2018, 10:42 AM
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Incredible 850s with a unique and strong moisture transport




O BOY! cimms updated their tpw page. amazing visuals

here is NA total precipatble water



http://tropic.ssec.wisc.edu/real-time/mtpw2/

please check out their new TPW2 site and bookmark it. no doubt it wll be useful for the remainder of the tropical season into winter

This post has been edited by PoconoSnow: Jul 21 2018, 10:42 AM


--------------------
Ensemble Primer use only for real forecasting :)
http://www.wpc.ncep.noaa.gov/ensembletraining/
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stretchct
post Jul 21 2018, 11:08 AM
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Just left LBI. Hoping to outrun this. Clouds are flying by overhead and its breezy at Forked River stop.


--------------------



First Torn. warn May 15. 5 confirmed in WCT/HV
First STW: May 3rd (no T-storm imby)
First 90+ day: May 3, 92.8
First 80+ day: May 2, 89.2
First 70+ day: Feb 22, 77
Days over 90: 1
To make degree symbol: hold ALT type 0176 on numeric keypad

--------------------------------
Seasonal snow - normal 44"

2017-2018 74.5"
2016-17: 58"
2015-16: 33.5"
2014-2015 57"
2013-2014 58.25"
2012-2013 64.5"
2011-2012 30.5"
2010-2011 79"
2009-2010 49"
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Undertakerson
post Jul 21 2018, 11:52 AM
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I have an outdoor music event to attend tonight. sad.gif Starts at 6, right when the heaviest stuff rolls in. That we've had two solid hours of drizzle/showers at minimum (and steady showers ATTM), I'm scrambling to make alternate arrangements so as to stay dry. Not that I didn't know it was going to rain, but the timing (as was mentioned earlier) is, well... earlier. I was hoping to get to late afternoon, at least, before any rain

GFS says the SLP gets to Chez UTS, about the same time as the party breaks up.

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yamvmax
post Jul 21 2018, 12:25 PM
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Storm looks much more west of where it was supposed to be. I was hoping for some heavy rain tonight. Thinking I might miss it.
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Undertakerson
post Jul 21 2018, 12:40 PM
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I never gave much thought to the JAX Rule, in the summertime laugh.gif laugh.gif

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QUOTE
Mesoscale Discussion 1119
NWS Storm Prediction Center Norman OK
1237 PM CDT Sat Jul 21 2018

Areas affected...far southern Georgia and northern Florida

Concerning...Severe Thunderstorm Watch 299...

Valid 211737Z - 211900Z

The severe weather threat for Severe Thunderstorm Watch 299
continues.

SUMMARY...Threat for isolated damaging wind will persist another 2-3
hours as storms continue through far southern Georgia into northern
Florida. A downstream WW is not anticipated, but a portion of WW 299
can be locally extended farther southeast if needed.

DISCUSSION...Line of storms from the eastern FL panhandle into
extreme southern GA continues developing southward at around 35 mph.
The storms are embedded within modest (20-30 kt) west northwesterly
deep-layer flow, and the downstream boundary layer has destabilized
with 2000-2500 J/kg MLCAPE. Some small bowing segments continue to
be observed within the line. However there has been a slight
weakening trend, possibly due to storms having moved south of
stronger winds aloft as well as poor mid-level lapse rates
associated with very warm air (-3.6 C) with an inversion at 500 mb.
Nevertheless, low-level convergence along the leading gust front and
strong heating of the moist surface layer should continue to support
forward propagation next few hours along with a threat for isolated
damaging wind into mid afternoon.

..Dial.. 07/21/2018

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...JAX...TAE...

LAT...LON 30228398 30508333 30458240 30508189 30598158 30128150
29638197 29648326 30228398

Top/All Mesoscale Discussions/Forecast Products/Home


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Undertakerson
post Jul 21 2018, 12:47 PM
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QUOTE(PoconoSnow @ Jul 21 2018, 11:42 AM) *
Incredible 850s with a unique and strong moisture transport


O BOY! cimms updated their tpw page. amazing visuals

here is NA total precipatble water



http://tropic.ssec.wisc.edu/real-time/mtpw2/

please check out their new TPW2 site and bookmark it. no doubt it wll be useful for the remainder of the tropical season into winter

This post pins the crux of the matter for the heaviest QPF - centering right into Central PA and Lehigh Valley, including Phila NW region.

That transport seems to have gotten a touch stronger (as is logical with a developing coastal to our S/E). CTP now concedes that the meso model depiction of west track is to be believed. FF Watches now posted.


They are going slightly against WPC - what happened at that office, they (seemingly) suddenly, start to not, simply, regurgitate. I like.

.
QUOTE
NEAR TERM /THROUGH TONIGHT/...
*Increasing confidence in heavy rain and potential flooding
over south central PA this evening into tonight

The latest hires models and ensembles indicate a clear westward
shift in the heavy QPF axis associated with hybrid low tracking
north from the NC/VA coast. The highest QPF amounts are now
focused into south central PA. Therefore, several adjustments
were made to POP/QPF grids this morning to match the emerging
westward and increasing trends in the hires data. An expansion
of the flash flood watch is also likely with the next update.

There are several contributing factors to what could be a very
heavy rain event across parts of south central PA. Anomalous
east-southeast LLJ transports tropical moisture into the area
with PW values 2+ inches. There is very strong convergence and
lift progged at the nose of LLJ which should overcome a general
lack of instability/poor lapse rates. The greatest threat
appears to come from a deformation axis that should pivot/move
slowly over south central PA.

The main uncertainty is with the magnitude of rainfall amounts
and how that relates to flooding potential, given the dry
antecedent conditions and rather high 3-6hr flash flood
guidance (FFG). Will the lack of instability be overcome in
order to produce rain rates heavy enough to threaten FFG? WPC
is not buying in entirely on the hires model signal. We did
coordinate on an expanded coverage of the D1 slight risk to
cover more of south-central PA.
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Undertakerson
post Jul 21 2018, 12:50 PM
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And NE is "ne"-xt.

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