SWODY1
SPC AC 011949
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0249 PM CDT WED JUL 01 2009
VALID 012000Z - 021200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE MID
ATLANTIC STATES NEWD INTO NY/VT...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE
NRN/CENTRAL HIGH PLAINS...
...MID ATLANTIC/SRN NEW ENGLAND...
CURRENT FORECAST APPEARS GENERALLY ON TRACK. MINOR CHANGES TO SEVERE
THREAT INCLUDES REMOVING SRN VA OUT OF SLIGHT RISK AS VSBY IMAGERY
SUGGESTS STRONG SUBSIDENCE HAS SPREAD INTO THIS AREA BEHIND UPPER
IMPULSE MOVING THROUGH THE VA/MD PANHANDLES. WAVE THAT AIDED
STRONGER CONVECTION ACROSS SRN NEW ENGLAND HAS LIFTED NORTH OF AREA
AND WIDESPREAD CONVECTION HAS MOSTLY STABILIZED BOUNDARY LAYER AND
REDUCED SEVERE THREAT ACROSS RI/ERN MA AND ERN CT. SLIGHT RISK HAS
BEEN EXTENDED NWD ACROSS ERN NY/VT WHERE STRONGER HEATING AND
FAVORABLE 18Z ALB SOUNDING SUGGEST SUFFICIENT SHEAR/INSTABILITY FOR
A FEW STORMS FURTHER NWD THAN EARLIER INDICATED/REF WW 536.
...NRN CENTRAL PLAINS...
EARLIER SEVERE STORMS NEAR THE BLACK HILLS DISSIPATED AS THEY MOVED
EWD INTO A MORE STABLE BOUNDARY LAYER AWAY FROM THE HIGHER TERRAIN.
HOWEVER...STORMS ARE INITIATING NEAR THE HIGHER TERRAIN OF MT/WY AND
SHOULD SHIFT ESEWD INTO THE RISK AREA THIS AFTERNOON/EVENING AS
UPPER IMPULSE MOVES FROM WY INTO SD. AFTER STORMS DEVELOP LATER
TODAY...STORM OUTFLOWS SHOULD MERGE INTO A CLUSTER TONIGHT AND MOVE
SSEWD INTO NEB AS LOW LEVEL JET STRENGTHENS.
..SRN/CENTRAL AZ...
CLOUDS ARE CLEARING IN SRN/CENTRAL AZ AND STORMS ARE DEVELOPING OVER
THE HIGHER TERRAIN IN ERN AZ/WRN NM. ELY WINDS BETWEEN 500-700 MB
ARE LIKELY TO DRIVE THE STORMS WWD DURING THE LATE AFTERNOON/EVENING
HOURS...WITH A STRONG WIND GUST OR TWO POSSIBLE AS TEMPERATURES WARM
INTO THE 90S AND ABOVE 100 DEGREES IN SOME LOCATIONS.
..IMY.. 07/01/2009
.PREV DISCUSSION... /ISSUED 1121 AM CDT WED JUL 01 2009/
...MID ATLANTIC/SRN NEW ENGLAND...
UPPER LOW WILL REMAIN STATIONARY OVER ONTARIO/GREAT LAKES REGION
THROUGH THE PERIOD...WITH SEVERAL WELL DEFINED IMPULSES ROTATING
AROUND THIS FEATURE EVIDENT ON WV IMAGERY THIS MORNING. SHORTWAVE
TROUGH NOW EJECTING ACROSS THE CENTRAL APPALACHIANS SHOULD BE
PRIMARY FEATURE OF INTEREST REGARDING SEVERE THUNDERSTORM
DEVELOPMENT ENEWD THROUGH THE EVENING. HOWEVER...LEAD IMPULSE NOW
SUSTAINING STORMS OFF THE MID ATLANTIC COAST INTO SRN NEW ENGLAND
MAY SUSTAIN AT LEAST A LOW RISK OF SEVERE HAIL/STRONGER GUSTS INTO
THE EARLY TO MID AFTERNOON.
MORNING SURFACE ANALYSIS INDICATES RICHER BOUNDARY LAYER MOISTURE
HAS BEEN SHUNTED ALONG AND JUST OFF THE COAST WITH LEADING
FRONT/TROUGH. THIS LEAVES LOWER 60F SURFACE DEW POINTS HOLDING JUST
EAST OF THE MOUNTAINS FROM VA INTO CENTRAL PA/NY...WHERE VIS IMAGERY
IS MAINTAINING MOSTLY CLEAR SKIES. WITH BOUNDARY LAYER
HEATING/STEEPENING LOW LEVEL LAPSE RATES...A FEW STRONGER STORMS
SHOULD PERSIST OFF HIGHER TERRAIN THIS AFTERNOON/EVENING WITH
THREATS OF HAIL AND ISOLATED DAMAGING WINDS. WLY FLOW ALOFT WILL BE
A BIT STRONGER FROM PORTIONS OF VA INTO THE CHESAPEAKE REGION THIS
AFTERNOON WHICH WILL NOSE INTO SRN NEW ENGLAND THIS
EVENING...SUGGESTING ACTIVITY MAY BE A BIT MORE ORGANIZED IN THE
FORM OF SMALL SCALE BOWS/BRIEF SUPERCELLS WITH A SLIGHTLY GREATER
RISK OF DAMAGING WINDS.
...NRN/CENTRAL HIGH PLAINS...
SHORTWAVE TROUGH EMBEDDED WITHIN THE NRN STREAM /NOW OVER
ALBERTA-WRN MT/ WILL CLIP THE NRN HIGH PLAINS REGION THIS AFTERNOON.
AS THIS OCCURS...SECONDARY SYSTEM LOSING DEFINITION AS IT MOVES
THROUGH NRN PERIPHERY OF UPPER RIDGE HOLDING OVER THE SRN-CENTRAL
ROCKIES...WILL EMERGE INTO THE CENTRAL HIGH PLAINS LATER TODAY AND
TONIGHT. SUFFICIENT SURFACE-H85 MOISTURE WILL REMAIN IN PLACE OVER
THE REGION FOR AXIS OF MODERATE INSTABILITY EXTENDING FROM
WRN/CENTRAL NEB INTO WRN ND/ERN MT THIS AFTERNOON...WITH ERN BOUND
OF INSTABILITY LIMITED BY WRN EDGE OF SURFACE ANTICYCLONE EXTENDING
INTO THE ERN/CENTRAL DAKOTAS.
EXPECT DEEP ASCENT AHEAD OF NRN STREAM SYSTEM WILL OCCUR NEAR
SURFACE LOW/SURFACE COLD FRONT ADVANCING ACROSS OVER THE NRN HIGH
PLAINS FOR SEVERE THUNDERSTORM DEVELOPMENT BY THE MID AFTERNOON.
ADDITIONAL...MORE SCATTERED...DEVELOPMENT IS EXPECTED SPREADING EWD
INTO THE CENTRAL HIGH PLAINS THROUGH THE AFTERNOON/EVENING. SHEAR
WILL BE SUPPORTIVE OF SUPERCELLS...LIKELY HIGH-BASED...WITH THE
INITIAL DEVELOPMENT. HOWEVER...EVOLUTION INTO ONE OR MORE CLUSTERS
IS EXPECTED DURING THE EVENING SHIFTING SSEWD. LARGE HAIL AND
ISOLATED DAMAGING WINDS ARE EXPECTED TO BE PRIMARY SEVERE THREATS.
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