Sunday, September 12, 2010

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 121728
SWODY2
SPC AC 121726

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1226 PM CDT SUN SEP 12 2010

VALID 131200Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PART OF THE CENTRAL
PLAINS...

...SYNOPSIS...
MODELS MAINTAIN A LOW AMPLITUDE LARGE SCALE PATTERN ACROSS THE CONUS
THROUGH DAY 2. A COUPLE OF MIDLEVEL IMPULSES WILL TRACK SEWD FROM
THE GREAT LAKES ACROSS NY INTO WRN/SRN NEW ENGLAND AIDING IN THE
DEVELOPMENT OF CONVECTION/LOW-TOPPED TSTMS ON MONDAY. MEANWHILE...A
WNWLY MID-UPPER LEVEL FLOW REGIME WILL PERSIST FROM THE ROCKIES
THROUGH THE OH/TN VALLEYS TO THE MIDDLE/SRN ATLANTIC STATES...WITH
THE RIDGE AXIS BEING MAINTAINED ACROSS THE ROCKIES/ADJACENT HIGH
PLAINS.

...CENTRAL PLAINS AND PARTS OF MID-LOWER MO VALLEY...
A MIDLEVEL IMPULSE...CURRENTLY TRACKING ENEWD THROUGH THE NRN GREAT
BASIN PER WATER VAPOR IMAGERY...IS EXPECTED TO TRACK ESEWD FROM WY
INTO SD/NEB BY 14/00Z...AND THEN REACH IA/LOWER MO VALLEY BY 12Z
TUESDAY. A WEAKER IMPULSE...EMANATING FROM THE SRN ROCKIES
REGION...MAY PHASE WITH THE NRN STREAM FEATURE OVER THE CENTRAL
PLAINS TO LOWER MO VALLEY DURING THE SECOND HALF OF THE PERIOD. IN
THE LOW LEVELS...MODELS SUGGEST A COUPLE OF GENERALLY E-W BOUNDARIES
WILL EXTEND FROM IA/NRN MO INTO NEB AND NEAR THE KS/NEB BORDER AT
12Z MONDAY. THE NEB PORTION OF THESE BOUNDARIES ARE EXPECTED TO BE
THE FOCI FOR LATE AFTERNOON/EARLY EVENING TSTM DEVELOPMENT AS WAA
INCREASES ALONG NOSE OF STRENGTHENING LLJ AND FORCING FOR ASCENT
INCREASES ALOFT WITH APPROACH OF WY IMPULSE.

LOW LEVEL MOISTENING /SURFACE DEWPOINTS IN THE LOW-MID 60S SPREADING
NWD TO NEB/ AND SURFACE HEATING BENEATH PLUME OF STEEP MIDLEVEL
LAPSE RATES /7-8 C PER KM/ EXTENDING EWD TO IA/LOWER MO VALLEY WILL
PROMOTE MUCAPE 1000-2000 J/KG ACROSS THE SLIGHT RISK AREA. THIS
COMBINED WITH 35-50 EFFECTIVE BULK SHEAR SUGGEST BOTH MULTICELLS AND
SUPERCELLS PRODUCING A THREAT FOR HAIL...DAMAGING WINDS AND A
TORNADO OR TWO ALSO POSSIBLE...ESPECIALLY WITH THE INITIAL ACTIVITY.
STRENGTHENING/VEERING NOCTURNAL LLJ INTO NEB TO IA MONDAY NIGHT
SUGGESTS UPSCALE GROWTH INTO AN MCS WILL BE POSSIBLE WITH HAIL AND
STRONG/DAMAGING WIND GUSTS BECOMING THE PRIMARY THREATS. THIS
OUTLOOK HAS EXPANDED THE SLIGHT RISK AREA GIVEN MODEL AGREEMENT WITH
DEGREE OF INSTABILITY AND QPF ACROSS NRN KS INTO NEB. SEVERE
WEATHER WILL BE POSSIBLE SWD THROUGH THE REST OF KS...BUT WEAKER
FORCING ALOFT SHOULD TEND TO LIMIT THE AMOUNT OF EVENTS...AND THUS
WILL MAINTAIN LOWER OVERALL SEVERE PROBABILITIES.

...NORTHEAST STATES/WESTERN NEW ENGLAND...
IT APPEARS THAT RELATIVELY LOW-TOPPED STORMS SHOULD DEVELOP
ALONG/AHEAD OF A COUPLE OF EWD ADVANCING WIND SHIFTS ATTENDANT TO A
PAIR OF MIDLEVEL IMPULSES TRACKING ACROSS THIS REGION ON DAY 2.
GIVEN THE POTENTIAL FOR MODEST DAYTIME DESTABILIZATION AND THE
DEVELOPMENT OF STEEP LOW TO MID LEVEL LAPSE RATES...IN CONJUNCTION
WITH MODERATELY STRONG/NEARLY UNIDIRECTIONAL W-NWLY FLOW...THE
STRONGEST STORMS WILL BE CAPABLE OF GUSTY WINDS AND HAIL THROUGH
MONDAY AFTERNOON/EARLY EVENING.

..PETERS.. 09/12/2010

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