Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 300549
SWODY1
SPC AC 300548

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1248 AM CDT MON MAY 30 2016

VALID 301200Z - 311200Z

...THERE IS A SLGT RISK OF SVR TSTMS NORTHERN/CENTRAL GREAT
PLAINS...

...THERE IS A MRGL RISK OF SVR TSTMS SOUTHERN HIGH PLAINS TO PARTS
OF UPPER MIDWEST...

...THERE IS A MRGL RISK OF SVR TSTMS PARTS OF NORTHEAST TO NORTHERN
NEW ENGLAND...

...SUMMARY...
ISOLATED TO WIDELY SCATTERED SEVERE STORMS WILL BE POSSIBLE ACROSS
PARTS OF THE NORTHERN AND CENTRAL GREAT PLAINS...MAINLY THIS
AFTERNOON AND EVENING. THE MAIN HAZARDS SHOULD BE LARGE HAIL AND
DAMAGING WINDS.

...SYNOPSIS...
A SHORTWAVE TROUGH OVER THE CANADIAN ROCKIES SHOULD REACH THE
NORTHERN GREAT PLAINS BY EARLY TUE. SURFACE CYCLOGENESIS SHOULD
OCCUR NEAR THE BLACK HILLS WITH THIS LOW TRACKING ACROSS SD BEFORE
HEADING NORTHEAST TOWARDS THE RED RIVER VALLEY. A COLD FRONT WILL
TRAIL FROM THIS LOW AND PUSH SOUTH ACROSS THE CENTRAL GREAT PLAINS
WITH A PORTION OF THE FRONT MERGING WITH THE DRYLINE NEAR NORTHWEST
KS THIS EVENING. ELSEWHERE...A SHORTWAVE TROUGH OVER MANITOBA SHOULD
REACH THE ONTARIO/QUEBEC BORDER AREA EARLY TUE. A LOW-AMPLITUDE
MID-LEVEL RIDGE WILL PERSIST OVER THE SOUTHERN HIGH PLAINS
DOWNSTREAM OF A NEARLY STATIONARY SHORTWAVE IMPULSE IN SOUTHERN
CA/SOUTHWEST AZ.

...NORTHERN AND CENTRAL GREAT PLAINS...
EXTENSIVE CONVECTIVE OVERTURNING OCCURRED ACROSS THE CENTRAL AND
SOUTHERN GREAT PLAINS ON SUNDAY. THIS HAS RESULTED IN A PERVASIVE
MODIFIED AIR MASS WITH POCKETS OF MIDDLE 60S SURFACE DEW POINTS
RELEGATED FROM THE LOWER MO VALLEY ON SOUTH. AS SUCH...MODEL
FORECASTS OF BUOYANCY THIS AFTERNOON APPEAR LIKELY TO BE OVERDONE
/ESPECIALLY THE NAM/. NEVERTHELESS...ROBUST INSOLATION ACROSS THE
HIGH PLAINS AND A PERSISTENT ELEVATED MIXED LAYER SHOULD FOSTER
STEEP TROPOSPHERIC LAPSE RATES...YIELDING WEAK TO MODERATE BUOYANCY
AT PEAK HEATING.

STRONG MID/UPPER-LEVEL WINDS WILL BE CONFINED TO THE BACKSIDE OF THE
SHORTWAVE TROUGH WHICH WILL RESULT IN MINOR AMPLIFICATION OF THE
WAVE DURING THE LATTER HALF OF THE PERIOD. EFFECTIVE SHEAR VALUES
OVER THE WARM SECTOR IN THE AFTERNOON/EVENING SHOULD LARGELY RANGE
FROM 25-35 KT. CONVECTION SHOULD COMMENCE NEAR THE SD/ND/MT BORDER
AREA DURING THE EARLY AFTERNOON AND DEVELOP/SPREAD EAST/SOUTH AS
CONVERGENCE STRENGTHENS ALONG THE COLD FRONT AND PRE-FRONTAL TROUGH
AMID WANING MLCIN. SEVERE HAIL SHOULD BE THE PRIMARY INITIAL
HAZARD...TRANSITIONING TO A MIX OF WIND/HAIL AS HODOGRAPHS TEND TO
FAVOR MULTICELL CLUSTER MODE.

...SOUTHERN HIGH PLAINS...
ONGOING MCS OVER THE TX BIG COUNTRY TO CONCHO VALLEY HAS A
PRONOUNCED SOUTHWARD-MOVING OUTFLOW ACROSS THE PERMIAN BASIN AS OF
05Z. 00Z NAM/GFS GUIDANCE ARE WOEFULLY UNDERDONE WITH THE SOUTHERN
EXTENT AND STRENGTH OF THE COLD POOL. IT APPEARS THIS OUTFLOW MAY
REACH THE RIO GRANDE EARLY THIS MORNING AND ESSENTIALLY WIPE OUT THE
WESTERN PERIPHERY OF MARITIME TROPICAL AIR CURRENTLY OVER THE
EDWARDS PLATEAU. SHOULD THIS OCCUR...STORM DEVELOPMENT FARTHER WEST
THIS AFTERNOON WILL BE WITHIN A MODIFIED AIR MASS THAT IS LIKELY TO
BE SUBSTANTIALLY LESS BUOYANT THAN PROGGED BY 00Z GUIDANCE.

THE AFTERNOON SYNOPTIC PATTERN WILL REMAIN SIMILAR TO SUNDAY WITH
WEAK LOW/MID-LEVEL WINDS AND MODERATE SPEED SHEAR IN THE MID/UPPER
LEVELS. ISOLATED TO SCATTERED STORMS SHOULD FORM OVER THE HIGHER
TERRAIN AND ALONG THE DRYLINE...SPREADING EAST ACROSS WEST TX INTO
THE EVENING. ISOLATED OCCURRENCES OF SEVERE HAIL/WIND WILL BE
POSSIBLE...BUT THE OVERALL RISK SHOULD BE TEMPERED BY WEAKER
BUOYANCY RELATIVE TO SUNDAY.

...NORTHEAST TO NORTHERN NEW ENGLAND...
THICK CLOUD COVERAGE ACROSS THE REGION EARLY THIS MORNING SHOULD
SHIFT EAST AND ALLOW FOR POCKETS OF ROBUST INSOLATION AHEAD OF A
WEAK COLD FRONT PUSHING EAST ACROSS THE REGION THIS AFTERNOON.
ALTHOUGH SURFACE DEW POINTS SHOULD MIX INTO THE UPPER 50S TO LOWER
60S WHERE STRONGER HEATING OCCURS...WEAK BUOYANCY SHOULD DEVELOP
AMID POOR MID-LEVEL LAPSE RATES. ON THE PERIPHERY OF 30-40 KT
500-700 MB FLOW...SETUP COULD YIELD A FEW SEMI-ORGANIZED MULTICELL
CLUSTERS WITH THE MAIN HAZARD BEING ISOLATED DAMAGING WINDS.

..GRAMS/DEAN.. 05/30/2016

$$



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