Skip to content

Jul 31, 2013 1300 UTC Day 1 Convective Outlook

July 31, 2013

Jul 31, 2013 1300 UTC Day 1 Convective Outlook

day1otlk

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0751 AM CDT WED JUL 31 2013

VALID 311300Z – 011200Z

…THERE IS A SLGT RISK OF SVR TSTMS ACROSS PART OF THE CENTRAL PLAINS TO MID MO VALLEY…

…CENTRAL PLAINS TO MID MO VALLEY…
06Z MODELS CONTINUE TO INDICATE A CORRIDOR OF MODERATE INSTABILITY WILL DEVELOP INTO THE AFTERNOON FROM WRN KS INTO CENTRAL AND ERN NEB. THE NRN EXTENT OF THE SLIGHT RISK AREA WILL BE ALONG THE SRN PERIPHERY OF 50-60 KT NWLY MIDLEVEL WINDS…AND THUS STRONGER BULK SHEAR. DESPITE WEAK LOWER TROPOSPHERIC WINDS ACROSS THE SLIGHT RISK AREA…MODELS SUGGEST EFFECTIVE BULK SHEAR EVEN SWD INTO WRN KS WILL BE SUFFICIENT FOR STORM ORGANIZATION. SOME UNCERTAINTY EXISTS WITH TSTM COVERAGE THIS AFTERNOON…THOUGH THE DEGREE OF INSTABILITY AND SHEAR IS SUFFICIENT TO MAINTAIN THE SLIGHT RISK AREA. STRAIGHT HODOGRAPHS WILL FAVOR STORM SPLITS WITH HAIL AND DAMAGING WINDS BEING THE PRIMARY THREATS. A STRENGTHENING SLY LLJ INTO WRN/CENTRAL NEB THIS EVENING THROUGH TONIGHT WILL RESULT IN AN INCREASE IN WAA AND A THREAT FOR ELEVATED TSTMS…SOME BEING SEVERE WELL AFTER DARK.

…UPPER MS VALLEY/WRN GREAT LAKES…
A MIDLEVEL IMPULSE THAT TRACKED EWD ACROSS THE DAKOTAS PRIOR TO THE START OF DAY 1 WILL PROGRESS ESEWD INTO THE GREAT LAKES TODAY. THIS WILL OCCUR AS A MORE PRONOUNCED SHORTWAVE TROUGH OVER SRN MANITOBA/NWRN ONTARIO SHIFTS EWD AND THE ATTENDANT TROUGH AMPLIFIES SEWD FROM NRN MN INTO THE UPPER MS VALLEY AND GREAT LAKES THIS FORECAST PERIOD. FORCING FOR ASCENT WITH THE WEAKENING IMPULSE SHOULD MAINTAIN THE ONGOING CONVECTION AS IT MOVES ACROSS NRN WI AND PARTS OF UPPER MI THIS MORNING. MEANWHILE…ASCENT ATTENDANT TO HEIGHT FALLS WITH THE MORE PROMINENT AMPLIFYING TROUGH SHOULD RESULT IN TSTMS ACROSS MAINLY UPPER MI…ERN WI INTO NRN IL TO IA THIS AFTERNOON. A STRENGTHENING OF WNWLY MIDLEVEL WINDS/BULK SHEAR ACROSS THIS REGION COMBINED WITH MLCAPE VALUES TO AROUND 1000 J/KG SUGGEST THE STORMS THAT DO FORM WILL HAVE THE POTENTIAL TO BE ORGANIZED…PRODUCING A FEW STRONGER WIND GUSTS AND HAIL. HOWEVER…THE LACK OF STRONGER LOW LEVEL CONVERGENCE EXPECTED ACROSS THESE STATES SHOULD TEND TO LIMIT THE TSTM COVERAGE…AND THUS MAINTAIN LOW SEVERE WIND/HAIL PROBABILITIES. RECENT MODELS SUGGEST A FEW CHANGES TO THESE LOW SEVERE PROBABILITIES WITH AN EXTENSION SWD INTO NRN IL AND NWD INTO PART OF UPPER MI.

…CASCADE REGION OF ORE/WA…
MODELS SUGGEST THE CLOSED LOW CENTERED OFF THE PACIFIC NORTHWEST COAST WILL SHIFT VERY SLOWLY EWD TODAY…WHILE AT LEAST ONE MIDLEVEL IMPULSE ROTATES NWD THROUGH THE ERN PERIPHERY OF THIS SYSTEM ACROSS WRN PARTS OF ORE/WA. EARLY MORNING WATER VAPOR IMAGERY SHOWED ONE SUCH IMPULSE LOCATED OFF THE COAST OF NWRN CA. MARGINAL INSTABILITY /MLCAPE AROUND 500 J PER KG/ SHOULD DEVELOP BY LATE AFTERNOON INTO THE EARLY EVENING. THIS COMBINED WITH EFFECTIVE BULK SHEAR OF 25-35 KT WILL PROVE SUFFICIENT FOR A FEW ORGANIZED STORMS WITH A THREAT FOR STRONG WIND GUSTS AND SOME HAIL.

…SERN STATES…
WEAK HEIGHT FALLS…PW VALUES AROUND 2 INCH PER 12Z SOUNDINGS AND SOME DESTABILIZATION TODAY WILL SUPPORT ADDITIONAL SHOWERS AND TSTMS ACROSS THE SERN STATES THIS FORECAST PERIOD. VISIBLE SATELLITE IMAGERY EARLY THIS MORNING SHOWED EXTENSIVE CLOUDINESS EXTENDING FROM THE SRN APPALACHIANS THROUGH THE SERN STATES THAT SHOULD LIMIT SURFACE HEATING. UNCERTAINTY IN THE DEVELOPMENT OF GREATER INSTABILITY INTO THE AFTERNOON DUE TO THE CLOUDINESS AND WEAK DEEP LAYER SHEAR WILL LIMIT STORM ORGANIZATION. THE HIGH PW CONTENT AIR MASS COULD SUPPORT A FEW ENHANCED DOWNDRAFTS…BUT OVERALL LOW CONFIDENCE FOR THE LOCATION OF THE GREATEST THREAT AREA PRECLUDES THE INCLUSION OF LOW SEVERE WIND PROBABILITIES WITH THIS OUTLOOK ISSUANCE.

Advertisements

From → Weather Blog

Leave a Comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

w

Connecting to %s

%d bloggers like this: