2022 Mid-Atlantic Severe Wx Thread (General Discussion Etc)

[Eskimo Joe]

Flood Watch out...some spicy language:

Quote

DISTRICT OF COLUMBIA-FREDERICK MD-CARROLL-NORTHERN BALTIMORE-
SOUTHERN BALTIMORE-PRINCE GEORGES-ANNE ARUNDEL-NORTHWEST MONTGOMERY-
CENTRAL AND SOUTHEAST MONTGOMERY-NORTHWEST HOWARD-CENTRAL AND
SOUTHEAST HOWARD-NORTHWEST HARFORD-SOUTHEAST HARFORD-PRINCE
WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX-ARLINGTON/FALLS
CHURCH/ALEXANDRIA-WESTERN LOUDOUN-EASTERN LOUDOUN-
INCLUDING THE CITIES OF SILVER SPRING, SOUTH GATE, BOWIE, ARLINGTON, 
ANNAPOLIS, MANASSAS, ODENTON, WESTMINSTER, DAMASCUS, FALLS CHURCH, 
PURCELLVILLE, BETHESDA, CHANTILLY, BALLENGER CREEK, CENTREVILLE, 
STERLING, COLLEGE PARK, REISTERSTOWN, COLUMBIA, HERNDON, ALEXANDRIA, 
SEVERNA PARK, GREENBELT, GERMANTOWN, LEESBURG, MCLEAN, CAMP SPRINGS, 
ROCKVILLE, JARRETTSVILLE, FREDERICK, ARNOLD, DALE CITY, 
SUITLAND-SILVER HILL, LAKE RIDGE, GAITHERSBURG, SEVERN, RESTON, 
MONTCLAIR, BALTIMORE, ELDERSBURG, CLINTON, GLEN BURNIE, ASHBURN, 
ELLICOTT CITY, WOODBRIDGE, WASHINGTON, ANNANDALE, FRANCONIA, 
COCKEYSVILLE, LISBON, LAUREL, AND ABERDEEN
1253 PM EDT FRI JUL 8 2022

...FLOOD WATCH IN EFFECT FROM 11 PM EDT THIS EVENING THROUGH 
SATURDAY AFTERNOON...

* WHAT...FLASH FLOODING CAUSED BY EXCESSIVE RAINFALL IS POSSIBLE.

* WHERE...WASHINGTON DC, MARYLAND AND NORTHERN VIRGINIA, INCLUDING 
  THE FOLLOWING AREAS: IN DC, DISTRICT OF COLUMBIA. IN MARYLAND, 
  ANNE ARUNDEL, CARROLL, CENTRAL AND SOUTHEAST HOWARD, CENTRAL AND 
  SOUTHEAST MONTGOMERY, FREDERICK MD, NORTHERN BALTIMORE, NORTHWEST 
  HARFORD, NORTHWEST HOWARD, NORTHWEST MONTGOMERY, PRINCE GEORGES, 
  SOUTHEAST HARFORD AND SOUTHERN BALTIMORE. IN NORTHERN VIRGINIA, 
  ARLINGTON/FALLS CHURCH/ALEXANDRIA, EASTERN LOUDOUN, FAIRFAX, 
  PRINCE WILLIAM/MANASSAS/MANASSAS PARK AND WESTERN LOUDOUN.

* WHEN...FROM 11 PM EDT THIS EVENING THROUGH SATURDAY AFTERNOON.

* IMPACTS...EXCESSIVE RUNOFF MAY RESULT IN FLOODING OF RIVERS, 
  CREEKS, STREAMS, AND OTHER LOW-LYING AND FLOOD-PRONE LOCATIONS.

* ADDITIONAL DETAILS...
  - SHOWERS ARE EXPECTED WITH SCATTERED THUNDERSTORMS LATE THIS
    EVENING INTO MIDDAY SATURDAY. AVERAGE RAINFALL AMOUNTS AROUND
    1 TO 3 INCHES ARE EXPECTED, BUT LOCALIZED AMOUNTS AROUND 4 TO
    7 INCHES IN HEAVIER SHOWERS AND THUNDERSTORMS. RAINFALL
    AMOUNTS AROUND 1 TO 3 INCHES WITHIN AN HOUR OR TWO ARE
    POSSIBLE IN AREAS WHERE THE HEAVIEST RAINFALL OCCURS. THE
    BEST CHANCE FOR THE HEAVIEST RAINFALL WILL BE OVERNIGHT INTO
    SATURDAY MORNING.
  - PLEASE VISIT HTTP://WWW.WEATHER.GOV/SAFETY/FLOOD FOR
    INFORMATION ON FLOOD SAFETY.

 

[jewell2188]

Can someone explain the 3 county gap in between the watch zone lmao???

[Eskimo Joe]

^Gap is possible because:

1.) Terrain features can enhance flooding, plus they have lower FFG.

2.) Metro areas are rather vulnerable to flooding and have lower FFG.

Elsewhere, looks like guidance isn't hammering them much and they've been a bit drier. Just my two cents.

[mattie g]

29 minutes ago, Eskimo Joe said:

Flood Watch out...some spicy language:

 

No thanks on 4-7" of rain.

I'll take 3" if I have to, but even then it's pretty inconvenient.

[WxUSAF]

2 hours ago, Eskimo Joe said:

@WxUSAFreturns and the rain runs away.

Watering when I get back???

[H2O]

So storm cancel with the euro?  

[yoda]

DPs are already in the low 70s out... yuck

[Eskimo Joe]

52 minutes ago, H2O said:

So storm cancel with the euro?  

Euro shunts the axis of heaviest rainfall over to Delmarva and speeds everything up. It's almost like winter...lol.

[aldie 22]

Euro says keep my sprinklers ready

[MN Transplant]

18z NAM nest puts down some 10-15" values in spots by Charlottesville, but that model has terrain issues.

[H2O]

8 minutes ago, MN Transplant said:

18z NAM nest puts down some 10-15" values in spots by Charlottesville, but that model has terrain issues.

I think it has brain issues too

[aldie 22]

13 minutes ago, MN Transplant said:

18z NAM nest puts down some 10-15" values in spots by Charlottesville, but that model has terrain issues.

wait isn't it supposed to see the terrain?

[MN Transplant]

2 minutes ago, leesburg 04 said:

wait isn't it supposed to see the terrain?

Yes, but it overexaggerates the impact.

[batmanbrad]

WPC just placed a tiny bullseye of moderate risk for excessive rainfall right over the DC metro area:

...Ohio Valley, Central Appalachians, Mid-Atlantic
1930 UTC Update -- Per collaboration with WFO LWX, have hoisted a 
Moderate Risk area over parts of the Balt-Wash area for more 
widespread convection later tonight and into tomorrow morning 
(early portion of the Day 2 ERO period). There continues to be a 
multi-model heavy rainfall signal, especially from the CAMs, 
though the 18Z HRRR has broken a bit from the consensus by now 
showing the max QPF footprint a little farther south into Southern 
MD and the Northern Neck of VA. Will continue to keep an eye on 
observational and mesoanalysis trends this evening; for now have 
aligned the Moderate Risk area up with the general multi-model 
consensus, which also incorporates the more elevated 1 and 3 hour 
QPF exceedance probabilities per the 12Z HREF.

[North Balti Zen]

meh. 

[southmdwatcher]

So this is going to be a southern MD/central VA event??.......well at least most of us have relatively dry ground

[jewell2188]

21 minutes ago, southmdwatcher said:

So this is going to be a southern MD/central VA event??.......well at least most of us have relatively dry ground

?? I think this is going to be a DC north into Baltimore event. It looks like a zone from 66 south to perhaps Charlottesville give or take will be the screw zone with the exception of some pockets of heavy amounts. 

[Stormfly]

34 minutes ago, North Balti Zen said:

meh. 

Nothingburger stands are bigger than firework stands here in northern MD!

[North Balti Zen]

16 minutes ago, Stormfly said:

Nothingburger stands are bigger than firework stands here in northern MD!

I mean, event after event, winter or summer, sets up just south of up here.

 

double meh

[yoda]

What are the ARIs that LWX AFD talks about?

[batmanbrad]

According to https://www.allacronyms.com/ARI/weather_forecast

ARI stands for Accelerated Research Institute

[MN Transplant]

56 minutes ago, yoda said:

What are the ARIs that LWX AFD talks about?

Average Recurrence interval.

It is funny to see the AFD talk about widespread 1-3” with lollis to 4-7”, and then have the HRRR runs come in with virtually nothing for the metros.

 

 

[jewell2188]

5 minutes ago, MN Transplant said:

Average Recurrence interval.

It is funny to see the AFD talk about widespread 1-3” with lollis to 4-7”, and then have the HRRR runs come in with virtually nothing for the metros.

 

 

It would seem no matter where you are, this has extreme bust or boom potential. Knowing our area I would side with bust atm versus boom. 

[aldie 22]

34 minutes ago, MN Transplant said:

Average Recurrence interval.

It is funny to see the AFD talk about widespread 1-3” with lollis to 4-7”, and then have the HRRR runs come in with virtually nothing for the metros.

 

 

Various models this week have had anywhere from 2-4" for my area this week from both events it would be a total kick in the gnads to walk away with a big goose egg but it's certainly possible 

[09-10 analogy]

1 hour ago, MN Transplant said:

Average Recurrence interval.

It is funny to see the AFD talk about widespread 1-3” with lollis to 4-7”, and then have the HRRR runs come in with virtually nothing for the metros.

 

 

But I love me an ominous-sounding AFD, and this afternoon's was a good 'un. Standard deviations! Higher magnitudes of forcing! One to five-to-ten year ... event! (Just a "hint," though.) Area of greatest concern! A new one: "hydrophobic." All it missed, was "lollipops." But I guess that's more a snow thing?

This is NOT to poke fun at the forecasters at Sterling or the AFD's author! They are fantastic. I'm just a connoisseur of AFD's -- some of them are little works of art, I've saved Dewey's before PD2 somewhere -- and I always like the ones when the writer brings in a bit of drama.  

[Kay]

7 minutes ago, Kay said:

I'm just a connoisseur of AFD's

SAME. I too was savoring "hydrophobic".

edit: quoting fail

[kgottwald]

AFDs used to be a lot more interesting, varied and idiosyncratic back in the 1990s. A model "forecasting mins for planet Venus". "I just shake my head at the LFM." 

 

Nowadays they have to stick with their template: synopsis, short term, long term, and all the IDGAF stuff (aviation, marine, tides) at the bottom. All kind of samey,

[Kay]

2 hours ago, kgottwald said:

AFDs used to be a lot more interesting, varied and idiosyncratic back in the 1990s. A model "forecasting mins for planet Venus". "I just shake my head at the LFM." 

 

Nowadays they have to stick with their template: synopsis, short term, long term, and all the IDGAF stuff (aviation, marine, tides) at the bottom. All kind of samey,

Haha. I'd love to read some of those, didn't start till the 00s. AFDs were (are) a huge part of teaching myself about weather. Hit the glossary links and googled stuff etc.

I still think they can be entertaining. I religiously read Tides/Coastal Flooding. Aviation is often a good synopsis, too. However -- I do really miss WOODY! I could tell his writing style in a sentence or less

[batmanbrad]

Yes, Andy "Woody!" Woodcock, he was a trip.  I occasionally go to other WFO's to check out their AFD's - some can get very wordy/technical, I especially remember the Taunton (now Boston/Norton) office when there would be a coastal storm in winter or a tropical system in summer, the discussion was a bit like "War and Peace"!

[yoda]

Looks like Tuesday afternoon may be our last chance for some storms or even severe storms for the next 10 days or so -- from this afternoon's AFD:

 

With southerly flow and moisture return ahead of a cold front
Tuesday, temperatures will soar toward the low 90s for most
locales. PWs will increase through the day to near 1.75-2" east
of I-81 by the evening. Profiles show a decent overlap of CAPE
in the -10 to -20C layer on soundings, so there could be a large
hail threat in combination with a damaging wind threat in any
thunderstorm. There could be two rounds of thunderstorms: 1)
Along a lee-side pressure trough near and east of the Blue Ridge
and 2) With the frontal boundary itself. There is also
noteworthy shear for this time of year (40-50 kts of bulk
shear).