SWODY1
SPC AC 300600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT MON AUG 30 2010
VALID 301200Z - 311200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTHERN/CENTRAL
PLAINS AND UPPER MIDWEST...
...SYNOPSIS...
AN AMPLIFIED LONGWAVE PATTERN WILL PREVAIL OVER THE CONUS THROUGH
TODAY/TONIGHT. AS AN EASTERN STATES UPPER RIDGE REMAINS CENTERED
NEAR THE APPALACHIANS...THE BASAL PORTION OF THE CURRENT WESTERN
STATES UPPER TROUGH WILL EJECT/ACCELERATE NORTHEASTWARD OVER THE
GREAT BASIN/CENTRAL ROCKIES TODAY...AND REACH THE NORTHERN
PLAINS/CANADIAN PRAIRIES BY LATE TONIGHT. IN RESPONSE TO THE UPPER
TROUGH...SURFACE CYCLOGENESIS IS ANTICIPATED PRIMARILY ACROSS THE
DAKOTAS IN VICINITY A SOUTHWEST-NORTHEAST ORIENTED FRONTAL ZONE
ACROSS THE NORTH PLAINS...WITH A ROUGHLY NNE-SSW ORIENTED LEE TROUGH
ALSO SHARPENING ACROSS A BROAD LONGITUDINAL EXTENT OF THE HIGH
PLAINS.
...NORTHERN/CENTRAL PLAINS AND UPPER MIDWEST...
ALONG/NORTH OF THE AFOREMENTIONED NORTHERN PLAINS SURFACE
FRONT...SCATTERED ELEVATED TSTMS MAY POSE RISK OF ISOLATED SEVERE
HAIL ACROSS EASTERN MT INTO ND TODAY. SUCH A THREAT SHOULD MORE SO
INCREASE IN EARNEST THIS AFTERNOON AIDED BY THE ONSET OF MORE
CONSEQUENTIAL LARGE SCALE FORCING FOR ASCENT/HEIGHT FALLS. BY LATE
THIS AFTERNOON/EARLY EVENING...A MORE APPRECIABLE SURFACE BASED
SEVERE RISK SHOULD STEADILY EVOLVE ACROSS THE DAKOTAS/NEB IN
VICINITY OF THE SURFACE FRONTAL ZONE/SURFACE LOW...PERHAPS AIDED THE
NORTHEASTWARD ACCELERATION OF A MID LEVEL IMPULSE LOCATED ACROSS NM
OVERNIGHT. THE STRONGER VERTICAL SHEAR/COOLING ALOFT WILL LAG
/NORTHWEST OF/ THE MAJORITY OF THE DAKOTAS FRONTAL ZONE...BUT
INCREASING LARGE SCALE SUPPORT/MODERATE DESTABILIZATION AND A
NEAR-FRONTAL FAVORABLE JUXTAPOSITION OF VERTICAL SHEAR/BUOYANCY WILL
LIKELY YIELD A MARKED INCREASE IN SEVERE POTENTIAL BY LATE
AFTERNOON/EARLY EVENING.
IT APPEARS A SEVERAL HOUR WINDOW FOR SURFACE BASED QUASI-DISCRETE
SUPERCELLULAR STORMS...WITH A LARGE HAIL AND TORNADO RISK...WILL
EXIST MAINLY ACROSS THE EASTERN DAKOTAS LATE THIS AFTERNOON/EARLY
EVENING. THIS SHOULD PRIMARILY BE ALONG THE SURFACE FRONTAL ZONE
EAST-NORTHEAST OF A DEEPENING SURFACE LOW...WITH FORECAST SOUNDINGS
REFLECTIVE OF INCREASING LOW LEVEL SHEAR TOWARD/AFTER DARK
COINCIDENT WITH INCREASING LOW LEVEL RH. HOWEVER...DEEP LAYER FLOW
LARGELY ORIENTED PARALLEL TO THE SOUTHWEST-NORTHEAST ORIENTED
FRONTAL ZONE...WITH A VEER-BACK-VEER PATTERN NOTED WITH HEIGHT
THROUGH 2-5 KM PER FORECAST SOUNDINGS...IS SUGGESTIVE OF A
RELATIVELY QUICK QUASI-LINEAR EVOLUTION DURING THE EVENING HOURS.
THIS EVOLUTION IS SUPPORTED BY 00Z WRF-NMM EXPLICIT
GUIDANCE...FURTHERING THE IDEA THAT DAMAGING WINDS WILL EVOLVE INTO
THE DOMINANT CONCERN DURING THE EVENING. AS STORMS CONGEAL...STRONG
DEEP LAYER/LOW LEVEL FLOW WILL BE SUPPORTIVE OF ONE OR MORE
WELL-ORGANIZED LINEAR CLUSTERS WITH EMBEDDED BOWS FROM THE EASTERN
DAKOTAS INTO MN.
ACROSS THE HIGH PLAINS...IT SHOULD BE NOTED THAT OTHER LOWER
TOPPED/SURFACE BASED TSTMS MAY ALSO DEVELOP LATE THIS
AFTERNOON/EARLY EVENING ACROSS SOUTHEAST MT/NORTHEAST WY INTO THE
WESTERN DAKOTAS...ALONG/NORTH OF THE SOUTH-SOUTHEAST ADVANCING FRONT
AMID DEVELOPING LOW LEVEL UPSLOPE TRAJECTORIES. GIVEN COOL THERMAL
PROFILES ALOFT/STRONG VERTICAL SHEAR...THESE TSTMS COULD POSE A
SEVERE HAIL/DAMAGING WIND AND ISOLATED TORNADO RISK PROVIDED
SUFFICIENT DAYTIME HEATING/DESTABILIZATION.
SOUTH OF THE DAKOTAS...OTHER SEMI-ORGANIZED/SUSTAINED STRONG/SEVERE
STORMS INCLUDING A FEW SUPERCELLS ARE EXPECTED TO DEVELOP ACROSS
NEB/KS WITHIN A DEEPER MIXED BOUNDARY LAYER...WITH DAMAGING
WINDS/SOME SEVERE HAIL AS THE PRIMARY CONCERNS.
...SOUTHERN HIGH PLAINS...
A MORE ISOLATED SEVERE THREAT...PRIMARILY IN THE FORM OF
MULTICELLULAR CLUSTERS CAPABLE OF DOWNBURSTS...IS EXPECTED WITHIN A
NORTHEAST-SOUTHWEST CORRIDOR ACROSS THE SOUTHERN HIGH PLAINS THIS
AFTERNOON/EVENING. ALONG/EAST OF A SHARPENING HIGH PLAINS SURFACE
TROUGH...THIS REGIME WILL BE CHARACTERIZED BY WELL-MIXED BOUNDARY
LAYER/STEEP LOW LEVEL LAPSE RATES AND WEAK TO MODERATE BUOYANCY
COUPLED WITH MODEST SOUTHWESTERLY MEAN FLOW. GIVEN LIMITED HEIGHT
FALLS/COOLING ALOFT AT THIS LATITUDE AND RESULTANT WEAK LAPSE RATES
ALOFT/MODEST NATURE OF THE VERTICAL SHEAR /25-30 KT/...NOTHING MORE
THAN AN ISOLATED/MARGINAL SEVERE RISK IS CURRENTLY ANTICIPATED.
..GUYER/GRAMS.. 08/30/2010
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
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