Skip Navigation Links weather.gov 
NOAA logo-Select to go to the NOAA homepage NOAA's National Weather Service   Select to go to the NWS homepage
Storm Prediction Center
navigation bar left  
  navigation bar end cap


 
USA.gov is the U.S. Government's official Web portal to all Federal, state and local government Web resources and services.

    Day 2 Outlook >
Aug 22, 2017 1300 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Tue Aug 22 12:28:45 UTC 2017 (Print Version | 20170822 1300Z Day 1 shapefile | 20170822 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Tornado Wind Hail
 Population  Cities/Towns  CWAs  Interstates  Counties  ARTCC  FEMA Regions

 Forecast Discussion
   SPC AC 221228

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0728 AM CDT Tue Aug 22 2017

   Valid 221300Z - 231200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS MAINLY THIS
   AFTERNOON FROM EASTERN OH AND PA ACROSS NY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED RISK AREA...FROM KY TO WESTERN NEW ENGLAND...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM TN TO OK
   AND THE TX PANHANDLE...

   ...SUMMARY...
   Severe thunderstorms with damaging winds, and possibly a couple of
   tornadoes, are expected this afternoon from the upper Ohio Valley to
   Pennsylvania and New York.  Thunderstorms with isolated
   strong/damaging gusts will also be possible farther southwest into
   parts of the southern Plains.

   ...NY/PA to the southern Plains through late evening...
   A pronounced midlevel trough over the upper Great Lakes will
   continue to amplify while approaching Quebec tonight.  Associated
   surface cyclogenesis preceding the midlevel trough will drive a
   surface cold front southeastward across the lower Great Lakes and OH
   Valley by tonight.  In addition, the remnants of a subtropical speed
   max, enhanced by overnight convection across IL/MO, will accelerate
   east-northeastward over the OH Valley/PA/NY in advance of the
   primary midlevel trough, and in phase with the diurnal heating
   cycle.

   It appears that the primary focus for thunderstorm development today
   will a pre-frontal or the remnant outflow/differential heating zone
   on the leading edge of the ongoing convection from IN to MO. 
   Convection will likely strengthen/redevelop by midday or early
   afternoon across OH and western NY, and storms will subsequently
   spread eastward across PA/NY through the afternoon.  Midlevel flow
   and effective bulk shear will likewise strengthen into the 40-50 kt
   range from OH to PA/NY this afternoon, as surface heating results in
   steepening low-level lapse rates and MLCAPE near 1500 J/kg.  The
   primary convective evolution should a mixed mode transitioning to
   line segments, with the potential for downward momentum transfer and
   swaths of damaging winds with the more intense bowing segments. 
   Additionally, there will be a coincident increase in low-level
   shear/hodograph curvature across PA/NY during the afternoon in
   response to the cyclogenesis to the north.  Given the relatively
   moist environment, semi-discrete storms could pose a tornado threat,
   along with embedded QLCS mesovortices.  The large hail threat should
   remain marginal as a result of modest midlevel lapse rates.

   Deep-layer flow and shear will weaken with southward extent from KY
   into TN, and the weak-shear environment will extend westward along
   the surface cold front in the vicinity of I-40 in OK/TX this
   afternoon.  Loosely organized multicell clusters are expected along
   the front from TN across AR into OK/TX Panhandle, where isolated
   downbursts will be the main threat this afternoon/evening.

   ..Thompson/Smith.. 08/22/2017

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z

        
Top/Latest Day 2 Outlook/Today's Outlooks/Forecast Products/Home
Weather Topics:
Watches, Mesoscale Discussions, Outlooks, Fire Weather, All Products, Contact Us

NOAA / National Weather Service
National Centers for Environmental Prediction
Storm Prediction Center
120 David L. Boren Blvd.
Norman, OK 73072 U.S.A.
spc.feedback@noaa.gov
Page last modified: August 22, 2017
Disclaimer
Information Quality
Help
Glossary
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities