7/27 Severe Threat Discussion and Obs

[Eskimo Joe]

Is there any other model than the NAM/HRRR that is reliable for severe wx. It seems that we always get excited over a 48 hour view of the NAM then get let down when its the day before.

[Kmlwx]

Is there any other model than the NAM/HRRR that is reliable for severe wx. It seems that we always get excited over a 48 hour view of the NAM then get let down when its the day before.

I think that's more a factor of DC severe expectations/result. DC is not a severe town 90% of the time with some notable exceptions. We might get a good/major event for every 20-30 busts. Difficult to tell which this will be until the morning of probably. 

[StudentOfClimatology]

Only thing I'm worried about is cloud cover. If we can get some decent breaks in coverage I think we're game.

[PhineasC]

Probably another overhyped bust for the cities. Last few mega storms gave me drizzle and a few claps of thunder.

[mappy]

Ellinwood thinks SPC was a bit on the bullish side given the uncertainty. 6z NAM for us was definitely not like the 0z NAM. He thinks 30% somewhere east of the apps will be needed but still a lot to be worked out. We'll need to see more runs like the NAM of last night if we want to hold higher potential.

I saw the twitter convo....

[Kmlwx]

Probably another overhyped bust for the cities. Last few mega storms gave me drizzle and a few claps of thunder.

Always a safe bet - but probably one of the higher end threats we've seen this year. Breaks in cloud cover will really help as usual.

[yoda]

Looks like 12z NAM brought back the slight chance of something btwn 8pm and 12am per the soundings

[CAPE]

12z NAM...bulk shear, decent helicity, and instability coincide around 42 hr for parts of central MD, upper eastern shore into DE and SNJ.

[yoda]

12z NAM lights up the area just after 00z it would appear using the soundings... and once again those are quite impressive

[yoda]

Hello again curved hodo... pretty impressive looking

 

[yoda]

EZF:

 

 

 

DCA:

 

 

 

[yoda]

Don't remember this before from LWX... and looks like they already declared a "critical weather day" for tomorrow

 

http://ow.ly/i/6mb9Z

 

NWS DC/Baltimore ‏@NWS_BaltWash 44m

Severe weather becoming increasingly likely for Sunday PM. http://ow.ly/i/6mb9Z  Very important to stay tuned for updates.

[Kmlwx]

Don't remember this before from LWX... and looks like they already declared a "critical weather day" for tomorrow

 

http://ow.ly/i/6mb9Z

 

NWS DC/Baltimore ‏@NWS_BaltWash 44m

Severe weather becoming increasingly likely for Sunday PM. http://ow.ly/i/6mb9Z  Very important to stay tuned for updates.

 

http://www.nco.ncep.noaa.gov/pmb/cwd/

[CAPE]

How often are these issued?

 A critical weather event is defined as any of the following occurring on/near the coast of or within the United States and its territories (including Puerto Rico, the Virgin Islands and Guam):

1. A widespread tornado outbreak;

2. A storm system causing a major precipitation event;

3. A severe cold-season storm affecting a large area with widespread heavy snow, freezing rain, or blizzard conditions; or

4. A tropical system threatening the coastline or producing excessive rainfall after moving inland.

[yoda]

12z GFS looks like it supports the 12z NAM to a degree for tomorrow evening... I don't have the 03z sounding... but the 00z soundings at KIAD/DCA/EZF were all pretty decent

[chris87]

How often are these issued?

 

There are issued quite often -- a moderate risk always gets one.

[Kmlwx]

There are issued quite often -- a moderate risk always gets one.

 

What implications does it have? More balloon launches? 

[chris87]

What implications does it have? More balloon launches? 

 

Someone more tied into WPC operations could probably give you a better explanation but I think it's really just for internal coordination.

[CAPE]

Someone more tied into WPC operations could probably give you a better explanation but I think it's really just for internal coordination.

I think that is exactly it- coordination of resources to ensure timely delivery of info.

[chris87]

I think that is exactly it- coordination of resources to ensure timely delivery of info.

 

exactly, there's nothing really to read into with it -- they happen all the time -- this situation is no different than any other moderate risk is handled

[arlwx]

From Pittsburgh  AFD:

 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1248 PM EDT SAT JUL 26 2014

.SYNOPSIS...
SHOWER AND THUNDERSTORM CHANCES...WITH THE RISK OF SEVERE
WEATHER...WILL INCREASE THROUGH SUNDAY. COLDER WEATHER CAN BE
EXPECTED FOR NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
THE EARLY AFTN UPDATE FEATURED MORE ADJUSTMENTS TO POPS FOR LTR
TNGT AND SUNDAY AS THE NXT SHRTWV MOVG ACRS THE GREAT LAKES IS
EXPECTED TO SPAWN SOME SCT TSTMS LATE THIS AFTN AND THIS EVE.
STORMS OVR WRN OH AND IN ARE EXPECTED TO CONGEAL INTO AN
MCS...TRACK OF WHICH MAY CLIP ECNTRL OHIO TNGT. THE RISK OF SVR
WITH THAT IS SLGT...BUT HAS BEEN INCLUDED THE HAZARDOUS WEATHER OUTLOOK.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
THE PRIMARY CONCERN OF THE FORECAST EFFORT IS OF SUNDAY AS
DEEPENING SHRTWV IS PROJECTED ACRS THE GREAT LAKES AND TWD THE
UPR OH REGION. SEASONALLY STRONG JET STREAK WL INCRS THE MID AND
UPR WIND OVR BACKED SFC FLOW RESULTING IN SEVERE SPPRTG SPEED AND
DIRECTIONAL SHEAR. BNDRY POSITIONING AND INSTABILITY RMN THE
LIMITING FACTORS FOR THE UPR OH REGION GIVEN CLDS AND SHWR
DVLPMNT...BUT FALLING MID LVL TEMPS WITH THE ADVN OF THE MID LVL
THERMAL TROF ARE EXPECTED OFFSET...ESPECIALLY LTR IN THE DAY.

THE BOTTOM LINE IS THAT THE ENTIRE ARE HAS BEEN HIGHLIGHTED FOR A
FULL ARRAY SEVERE RISK...BETTER CHC FOR WHICH IS PROJECTED ALONG
AND SOUTH OF A ZANESVILLE TO MORGANTOWN LINE WHERE THE STORM
PREDICTION CENTER HAS DRAWN MODERATE PROBABILITIES IN VCNTY OF THE
EXPECTED FRONTAL POSITION.
 

[EasternUSWX]

Interesting best parameters are south, but risk shifted a bit north.

 

[yoda]

SIG SEVERE 103,416 25,251,674

Columbus, OH...Baltimore, MD...Washington, DC...Cleveland, OH...Pittsburgh, PA...

 

from 1730 OTLK

[Ian]

Less interesting discussion overall. Not that it matters

[arlwx]

DAY 2 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   1230 PM CDT SAT JUL 26 2014

   VALID 271200Z - 281200Z

   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF OH...NE KY AND
   WV...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE OH
   VALLEY...TN VALLEY...MID-ATLANTIC...PA...NY AND SRN NEW ENGLAND...

   ...SUMMARY...
   TORNADOES...DAMAGING WINDS AND LARGE HAIL ARE EXPECTED ACROSS MUCH
   OF EASTERN KENTUCKY...SOUTHERN OHIO AND WEST VIRGINIA DURING THE
   AFTERNOON AND EVENING. SEVERE WEATHER IS ALSO EXPECTED ACROSS MUCH
   OF THE MID-ATLANTIC AND NORTHEASTERN STATES WITH MAINLY DAMAGING
   WINDS AND HAIL. ISOLATED HAIL AND WIND IS ALSO POSSIBLE ACROSS
   SOUTHEASTERN ARIZONA.

   ...OH VALLEY/SRN GREAT LAKES AND CNTRL APPALACHIAN MTNS...
   A POSITIVELY-TILTED UPPER-LEVEL TROUGH WILL MOVE SEWD ACROSS THE WRN
   GREAT LAKES ON SUNDAY AS A WELL-DEFINED 60 TO 75 KT MID-LEVEL JET
   MOVES OVER THE MID MS VALLEY AND INTO THE OH VALLEY. AT THE SFC...A
   LOW WILL DEEPEN AND MOVE SEWD ACROSS THE GREAT LAKES REGION AS A
   COLD FRONT ADVANCES EWD INTO THE OH AND TN VALLEYS. THUNDERSTORMS
   MAY BE ONGOING ACROSS PARTS OF THE UPPER OH VALLEY AT THE START OF
   THE PERIOD. THIS ACTIVITY SHOULD EXPAND IN COVERAGE AS SFC TEMPS
   WARM AND MODERATE TO STRONG INSTABILITY DEVELOPS ACROSS MUCH OF THE
   OH VALLEY. SEVERAL CONVECTIVE CLUSTERS ARE FORECAST TO ORGANIZE
   DURING THE AFTERNOON WITH MODEL FORECASTS EXPANDING CONVECTIVE
   DEVELOPMENT NWD INTO THE SRN GREAT LAKES REGION AND NEWD ACROSS THE
   CNTRL APPALACHIAN MTNS BY LATE AFTERNOON. THE APPROACHING
   UPPER-LEVEL TROUGH AND ASSOCIATED MID-LEVEL JET ALONG WITH MODERATE
   TO STRONG INSTABILITY MAY SUPPORT THE DEVELOPMENT OF NUMEROUS SEVERE
   THUNDERSTORMS WITH THE POSSIBILITY FOR TORNADOES ACROSS PARTS OF THE
   OH VALLEY AND CNTRL APPALACHIAN MTNS FROM MIDDAY SUNDAY PERSISTING
   INTO THE AFTERNOON AND EVENING.

   NAM FORECAST SOUNDINGS ACROSS THE MODERATE RISK AREA FOR HUNTINGTON
   AND CHARLESTON WV AT 21Z/MON SHOW IMPRESSIVE THERMODYNAMIC AND SHEAR
   PROFILES. SFC DEWPOINTS ARE FORECAST TO BE IN THE LOWER 70S F WITH
   MLCAPE VALUES INCREASING INTO THE 2000 TO 3000 J/KG RANGE. IN
   ADDITION...0-6 KM SHEAR IS FORECAST TO BE IN THE 50 TO 60 KT RANGE
   WITH SHEAR GRADUALLY INCREASING DURING THE AFTERNOON. THIS SHOULD
   EASILY SUPPORT SUPERCELL DEVELOPMENT AS THE EXIT REGION OF THE
   MID-LEVEL JET OVERSPREADS THE MODERATE RISK AREA. THE STRONG SHEAR
   PROFILES SHOULD HELP MAINTAIN DISCRETE CELLS AND SUPERCELLS WILL BE
   LIKELY EVEN AS STORM COVERAGE INCREASES AND CELL MERGERS OCCUR
   DURING THE AFTERNOON. FORECAST SOUNDINGS ALSO SHOW 0-3 KM STORM
   RELATIVE HELICITIES IN THE 300 TO 400 M2/S2 SUGGESTING LOW-LEVEL
   SHEAR WILL BE FAVORABLE FOR TORNADOES. THE GREATEST POTENTIAL FOR
   SUPERCELLS WITH TORNADO POTENTIAL IS FORECAST TO BE WHERE THE EXIT
   REGION OF THE MID-LEVEL JET INTERSECTS THE LOW-LEVEL JET IN OH...ERN
   KY AND WV. A STRONG TORNADO OR TWO WILL BE POSSIBLE WITH THE MORE
   DOMINANT SUPERCELL STORMS. ANY STORM THAT CAN ROTATE WILL ALSO BE
   CAPABLE OF PRODUCING LARGE HAIL AND WIND DAMAGE. BOWING LINE
   SEGMENTS WITH WIND DAMAGE POTENTIAL SHOULD ALSO DEVELOP SUNDAY
   AFTERNOON IN THE MODERATE RISK AREA. THE SEVERE THREAT SHOULD ALSO
   IMPACT THE SRN GREAT LAKES AND PARTS OF THE TN VALLEY SUNDAY
   AFTERNOON WITH THE THREAT INCREASING ACROSS MD AND PA DURING THE
   LATE AFTERNOON.

   ...MID-ATLANTIC/PA/NJ/SRN NEW ENGLAND...
   A POSITIVELY-TILTED UPPER-LEVEL TROUGH WILL MOVE INTO THE WRN GREAT
   LAKES AS A LEAD SHORTWAVE TROUGH MOVES INTO THE MID-ATLANTIC ON
   SUNDAY. AT THE SFC...A TROUGH IS FORECAST TO BE IN PLACE FROM SRN
   NEW ENGLAND EXTENDING SSWWD INTO MD AND VA. SFC DEWPOINTS ALONG THE
   TROUGH SHOULD BE IN THE UPPER 60S F WITH MODERATE INSTABILITY
   DEVELOPING BY MIDDAY. SCATTERED THUNDERSTORMS APPEAR LIKELY TO
   INITIATE ALONG THE SFC TROUGH DURING THE AFTERNOON WITH SEVERAL
   STORM CLUSTERS MOVING ACROSS THE ATLANTIC COAST PLAINS.

   FORECAST SOUNDINGS ALONG THE SFC TROUGH FOR WASHINGTON DC AND NEW
   YORK CITY SUNDAY AFTERNOON SHOW MLCAPE IN THE 1500 TO 2000 J/KG
   RANGE WITH 30 TO 35 KT OF 0-6 KM SHEAR. THIS ALONG WITH STEEP
   LOW-LEVEL LAPSE RATES SHOULD BE FAVORABLE FOR WIND DAMAGE WITH THE
   STRONGER MULTICELLS. HAIL WILL ALSO BE POSSIBLE WITH ANY CELL THAT
   CAN EXHIBIT ROTATION. AN ISOLATED TORNADO OR TWO ALSO CAN NOT BE
   RULED OUT SUNDAY AFTERNOON.

   ...SE AZ...
   AN UPPER-LEVEL RIDGE WILL BE IN PLACE ACROSS THE FOUR CORNERS REGION
   SUNDAY WITH EAST SOUTHEASTERLY FLOW LOCATED ACROSS MUCH OF THE
   DESERT SOUTHWEST. AN AXIS OF MODERATE INSTABILITY SHOULD DEVELOP
   ACROSS SRN AND CNTRL AZ BY WITH NUMEROUS THUNDERSTORMS DEVELOPING BY
   SUNDAY AFTERNOON. FORECAST SOUNDINGS FOR PHOENIX AZ AT 21Z/SUN SHOW
   SFC DEWPOINTS NEAR 60 F WITH VERY STEEP LOW-LEVEL LAPSE RATES AND
   SFC TEMP-DEWPOINT SPREADS NEAR 40 DEGREES F. THIS SHOULD ENHANCE
   DOWNDRAFT ACCELERATION WITH THE STRONGER MULTICELLS MAKING A
   MARGINAL WIND DAMAGE THREAT POSSIBLE SUNDAY AFTERNOON.

   ..BROYLES.. 07/26/2014

   CLICK TO GET WUUS02 PTSDY2 PRODUCT

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z


   CURRENT UTC TIME: 1735Z (1:35PM), RELOAD THIS PAGE TO UPDATE THE TIME
 

[high risk]

   An important aspect of a critical weather day is that NCEP can not implement ANY changes to any operational model or product.

 

 

I think that is exactly it- coordination of resources to ensure timely delivery of info.

[Kmlwx]

Less interesting discussion overall. Not that it matters

Could also be related to it being different forecasters. Feel like we've seen this many times only for it to be strongly worded again on the new day 1 the following morning. 

High potential for both winning and busting I suppose as is usual here. 

[Kmlwx]

Like play doh being molded into new shapes lol

[needbiggerboat]

Like play doh being molded into new shapes lol

Thread needs a NSFW tag now.

[CAPE]

Interesting best parameters are south, but risk shifted a bit north.

 

 

You have to look at more than instability parameters. Location of the low level jet and best upper divergence occurs in Ohio and WV. Look at the upward vertical velocity and relative vorticity at 850, 700, and 500 mb.. It all comes together aloft over the moderate risk area.