Severe Storm Outlook Narrative (AC)
Issued by NWS

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ACUS01 KWNS 030553
SWODY1
SPC AC 030552

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1252 AM CDT TUE MAY 03 2016

VALID 031200Z - 041200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING
ACROSS PARTS OF THE CAROLINA PIEDMONT INTO THE SOUTHERN MID ATLANTIC
COASTAL PLAIN...

...THERE IS A MRGL RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE
SOUTHEAST STATES...INCLUDING THE EASTERN FLORIDA PENINSULA...

...SUMMARY...
SCATTERED STRONG TO SEVERE STORMS ARE POSSIBLE ACROSS PARTS OF THE
SOUTHEASTERN U.S. TODAY.

...SYNOPSIS...
MODELS INDICATE SOME WEAKENING OF THE UPPER HIGH CENTERED NEAR THE
MONTANA/ALBERTA BORDER DURING THIS PERIOD.  BUT UPPER RIDGING IS
EXPECTED TO REMAIN PROMINENT ACROSS MUCH OF WESTERN NORTH
AMERICA...WITHIN THE SPLIT BELTS OF WESTERLIES EMERGING FROM THE
MID-LATITUDE PACIFIC.  DOWNSTREAM OF THIS FEATURE...A STRONG SHORT
WAVE TROUGH /NOW DIGGING TO THE SOUTHWEST OF HUDSON BAY/ IS FORECAST
TO CONTINUE SOUTHWARD THROUGH MUCH OF THE UPPER MIDWEST BY 12Z
WEDNESDAY.  AS THIS OCCURS...INCREASED PHASING WITH TROUGHING NOW
DIGGING ACROSS THE CENTRAL PLAINS/MIDDLE MISSISSIPPI VALLEY APPEARS
PROBABLE...ALONG WITH FURTHER AMPLIFICATION OF LARGER-SCALE
TROUGHING ACROSS THE EASTERN U.S./GULF OF MEXICO/FLORIDA PENINSULA
AND WESTERN ATLANTIC.

IN LOWER LEVELS...A COLD FRONT IS EXPECTED TO MAKE FURTHER
SOUTHEASTWARD PROGRESS...THROUGH THE MID ATLANTIC COAST REGION...AND
GRADUALLY SOUTHEAST OF THE SOUTHERN APPALACHIANS THROUGH THE SOUTH
ATLANTIC AND EASTERN GULF COAST...WHILE STALLING AND WEAKENING OVER
THE WESTERN GULF OF MEXICO.  SEASONABLY MOIST CONDITIONS WILL REMAIN
CONFINED TO AREAS ALONG AND AHEAD OF THE FRONT...WHERE POTENTIAL FOR
STRONGEST STORMS WILL EXIST TODAY.  HOWEVER...FORCING FOR ASCENT AND
STRONG MID-LEVEL COOLING WITH THE IMPULSE DIGGING INTO THE UPPER
MIDWEST MAY ALSO CONTRIBUTE TO LOW-TOPPED THUNDERSTORM ACTIVITY.
SOMEWHAT SIMILAR CONDITIONS WITH A LESS VIGOROUS IMPULSE DIGGING
THROUGH THE SOUTH CENTRAL HIGH PLAINS AT PEAK HEATING MAY CONTRIBUTE
TO ADDITIONAL THUNDERSTORM ACTIVITY.

SOME MOISTENING ACROSS THE PACIFIC NORTHWEST INTO PARTS OF THE
NORTHERN ROCKIES...TO THE WEST OF THE WEAKENING RIDGING...AND AHEAD
OF UPPER TROUGHING APPROACHING THE PACIFIC COAST...MAY CONTRIBUTE TO
THE RISK FOR THUNDERSTORMS.  THIS MAY BE MOSTLY CONFINED TO WHERE
DAYTIME HEATING AND OROGRAPHIC FORCING LOCALLY ENHANCE
DESTABILIZATION AND LIFT.

...EASTERN GULF STATES/SOUTHERN MID ATLANTIC COAST STATES...
WEAK TO MODERATE BOUNDARY LAYER DESTABILIZATION...CHARACTERIZED BY
CAPE OF 1000-2000 J/KG BY LATE AFTERNOON...BENEATH CYCLONIC
MID-LEVEL FLOW WILL CONTRIBUTE TO THE POTENTIAL FOR VIGOROUS
CONVECTIVE DEVELOPMENT TODAY...PARTICULARLY FROM THE SAVANNAH VALLEY
NORTHEASTWARD THROUGH THE SOUTHERN MID ATLANTIC COAST.  IN THE WAKE
OF CONVECTION WHICH MAY STILL BE SPREADING ACROSS PARTS OF THE
COASTAL PLAIN EARLY TODAY...NEW CONVECTIVE DEVELOPMENT SEEMS MOST
LIKELY TO INITIATE NEAR THE MOUNTAINS TO THE WEST OF CHARLOTTE NC.
THIS ACTIVITY MAY BE AIDED BY FORCING ASSOCIATED WITH A ZONE OF
ENHANCED LOW-LEVEL WARM ADVECTION...DOWNSTREAM OF A WESTERLY 50-60+
KT 500 MB JET STREAK FORECAST TO NOSE ACROSS AND TO THE LEE OF THE
SOUTHERN APPALACHIANS DURING THE PEAK HEATING HOURS.  LOW-LEVEL
HODOGRAPHS MAY BE MODEST IN SIZE...BUT DEEP LAYER SHEAR WILL BE
FAVORABLE FOR SUPERCELL STRUCTURES CAPABLE OF PRODUCING SEVERE HAIL
AND DAMAGING WIND GUSTS.  THIS ACTIVITY IS EXPECTED TO SPREAD WITH
SUPPORTING FORCING FOR ASCENT...TOWARD THE SOUTHEAST
VIRGINIA/EASTERN NORTH CAROLINA COASTAL PLAIN THROUGH EARLY EVENING.

SOMEWHAT WEAKER LOW/MID-LEVEL FLOW...AND POTENTIAL BOUNDARY LAYER
DRYING BENEATH A MORE PRONOUNCED WESTERLY LOW-LEVEL FLOW
COMPONENT...PROVIDE MORE UNCERTAINTY CONCERNING STORM COVERAGE AND
INTENSITY TO THE SOUTHWEST OF THE SAVANNAH VALLEY.

...FLORIDA PENINSULA...
A PRONOUNCED WESTERLY COMPONENT TO THE 850 MB FLOW IS EXPECTED TO
FOCUS POTENTIAL FOR CONVECTIVE DEVELOPMENT ALONG THE ATLANTIC COAST
SEA BREEZE...WHERE VERTICAL SHEAR PROFILES BENEATH 30+ KT WEST
NORTHWESTERLY 500 MB FLOW MAY BECOME SUFFICIENT FOR SUPERCELLS.  THE
EXTENT OF THIS POTENTIAL REMAINS UNCLEAR...WITH GUIDANCE SUGGESTIVE
THAT CONSIDERABLE BOUNDARY LAYER DRYING WITH RELATIVELY DEEP MIXING
MAY TAKE PLACE DURING THE DAY OVER MUCH OF THE INTERIOR PENINSULA.

..KERR/PICCA.. 05/03/2016

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