SWODY2
SPC AC 290537
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1237 AM CDT SUN AUG 29 2010
VALID 301200Z - 311200Z
...THERE IS A SLGT RISK OF SVR TSTMS MON/MONDAY NIGHT ACROSS THE
NORTHERN PLAINS...
...SYNOPSIS...
MODELS CONTINUE TO INDICATE THAT A HIGH CENTER WILL REMAIN STRONG
OVER THE MID ATLANTIC COAST STATES THROUGH THIS PERIOD...WITHIN
BROADER SCALE SUBTROPICAL RIDGING...WHICH LIKELY WILL CONTINUE TO
ENCOMPASS MUCH OF THE SOUTHERN AND EASTERN U.S...ADJACENT WESTERN
ATLANTIC AND GULF OF MEXICO. THIS LATTER FEATURE ALSO APPEARS
LIKELY TO EXPAND WESTWARD ACROSS THE MEXICAN PLATEAU AND PARTS OF
THE SOUTHERN ROCKIES AND PLATEAU REGION...AS LARGER SCALE TROUGHING
BEGINS TO LIFT OUT OF THE WESTERN STATES...GENERALLY COINCIDENT WITH
THE NORTHEASTWARD ACCELERATION OF A SIGNIFICANT EMBEDDED SHORT WAVE
TROUGH OUT OF THE GREAT BASIN THROUGH THE CENTRAL CANADIAN/U.S.
BORDER AREA BY 12Z TUESDAY.
SOUTHWESTERLY MID/UPPER FLOW IS EXPECTED TO STRENGTHEN CONSIDERABLY
ACROSS MUCH OF THE CENTRAL AND NORTHERN PLAINS IN ASSOCIATION WITH
THE EVOLVING PATTERN...INCLUDING UP TO 50-70 KT AROUND 500 MB DURING
THE LATTER HALF OF THE PERIOD. MEANWHILE... STRONG SOUTHERLY
LOW-LEVEL FLOW BETWEEN THE EASTERN RIDGE AND A SURFACE TROUGH TO THE
LEE OF THE ROCKIES SHOULD BE MAINTAINED THROUGH MUCH OF THE PLAINS
INTO THE UPPER MISSISSIPPI VALLEY...AND PERHAPS EVEN STRENGTHEN
FURTHER MONDAY NIGHT IN RESPONSE TO THE ONSET OF SURFACE
CYCLOGENESIS. SUBSTANTIAL DIFFERENCES CONCERNING THIS PROCESS
CONTINUE TO EXIST AMONG THE VARIOUS MODELS...BUT IT STILL APPEARS
THAT THE PRIMARY SURFACE LOW WILL DEVELOP ACROSS SOUTHERN MANITOBA
INTO NORTHWESTERN ONTARIO LATE MONDAY NIGHT INTO TUESDAY.
...NORTHERN PLAINS...
WHILE THE CONFIDENCE IN THE EXISTENCE OF A SEVERE THUNDERSTORM
THREAT IS INCREASING FOR MONDAY/MONDAY NIGHT ACROSS PARTS OF
NEBRASKA AND THE CENTRAL/EASTERN DAKOTAS...INTO WESTERN
MINNESOTA...THE DETAILS OF THE POTENTIAL CONVECTIVE EVOLUTION...AND
THE MAGNITUDE OF THE THREAT...ARE A BIT MORE UNCERTAIN. THIS IS
PRIMARILY DUE TO THE POSSIBILITY OF A QUICKER RETURN OF HIGHER
BOUNDARY LAYER MOISTURE THAN PERHAPS EARLIER ANTICIPATED. AND THE
NAM...IN PARTICULAR...IS SUGGESTIVE OF THE DEVELOPMENT OF STRONGER
WARM SECTOR DEEP LAYER SHEAR...ACROSS THE EASTERN DAKOTAS/WESTERN
MINNESOTA BY EARLY MONDAY EVENING.
THERMODYNAMIC PROFILES ACROSS MUCH OF THE NORTHERN PLAINS ARE
EXPECTED TO BE CHARACTERIZED BY STEEP MID-LEVEL LAPSE RATES...AND AT
LEAST A NARROW PRE-FRONTAL CORRIDOR OF STRONG SURFACE HEATING
...ACROSS PARTS OF WESTERN/NORTH CENTRAL NEBRASKA THROUGH CENTRAL
SOUTH DAKOTA AND EASTERN NORTH DAKOTA...SHOULD YIELD A HOT AND
DEEPLY MIXED BOUNDARY LAYER. THIS IS STILL EXPECTED TO PROVIDE A
FOCUS FOR THE INITIATION OF STORMS LATE MONDAY AFTERNOON...AS THE
LEADING EDGE OF MID-LEVEL HEIGHT FALLS AND COOLING WEAKEN
INHIBITION. THIS ENVIRONMENT WILL BE FAVORABLE FOR SEVERE STORMS
...INCLUDING ISOLATED SUPERCELLS...WITH THE RISK FOR LARGE
HAIL...STRONG DOWNBURSTS AND SURFACE COLD POOL DEVELOPMENT
...ACCOMPANIED BY POTENTIALLY DAMAGING SURFACE GUSTS.
CONVECTION IS EXPECTED TO DEVELOP EASTWARD WITH AN ATTENDANT SEVERE
THREAT AT LEAST INTO EVENING HOURS. IT IS UNCLEAR FROM LATEST MODEL
DATA WHETHER STORMS WILL CONSOLIDATE INTO AN EVOLVING SQUALL
LINE...OR REMAIN AT LEAST SOMEWHAT DISCRETE IN NATURE. BUT AS
ACTIVITY ADVANCES EASTWARD INTO A MORE MOIST... AND MOISTENING
BOUNDARY LAYER...WITH SURFACE DEW POINTS INCREASING TO AROUND
70F...A WINDOW OF OPPORTUNITY APPEARS TO EXIST FOR THE DEVELOPMENT
OF TORNADIC SUPERCELLS ACROSS PARTS OF THE EASTERN DAKOTAS INTO
WESTERN MINNESOTA. THIS THREAT COULD PERSIST THROUGH THE 03-06Z
TIME FRAME...BEFORE DIMINISHING OVERNIGHT.
..KERR.. 08/29/2010
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment