Saturday, May 8, 2010
Days 4-8 outlooks
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 080851
SPC AC 080851
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0351 AM CDT SAT MAY 08 2010
VALID 111200Z - 161200Z
...DISCUSSION...
THE MEDIUM RANGE IS EXPECTED TO BE ACTIVE WITH TSTM EPISODES FROM
THE CNTRL/SRN PLAINS TO THE MIDWEST. MID-LVL WAVE THAT WILL BE
IMPETUS FOR A POTENTIALLY ACTIVE MONDAY IS EXPECTED TO DEAMPLIFY AND
MOVE ACROSS THE GRTLKS REGION ON TUESDAY. NEXT UPR TROUGH WILL
SETTLE INTO THE GRT BASIN EARLY NEXT WEEK IN ITS WAKE...THEN EJECT
ENE IN PIECES TOWARD THE MIDWEST. TIMING THESE SHORTWAVE TROUGHS
WILL BE CHALLENGING AND MEDIUM RANGE GUIDANCE EVEN VARIES ON THE
EVENTUAL EJECTION OF THE PARENT WAVE TOWARD THE PLAINS LATER IN THE
WEEK. PASSAGE OF EACH IMPULSE WILL INDUCE TSTM CLUSTERS THAT WILL
PROBABLY HAVE AN ATTENDANT SVR AND HVY RNFL THREAT. BUT...IN
ADDITION TO TIMING UNCERTAINTY...THERE WILL ALSO BE LOW
PREDICTABILITY ASSOCD WITH THE LATITUDINAL PLACEMENT OF THE
BAROCLINIC ZONE WHICH WILL BE HIGHLY INFLUENCED BY TSTM CLUSTERS.
Day 3 outlooks
SPC AC 080727
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0227 AM CDT SAT MAY 08 2010
VALID 101200Z - 111200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CNTRL/SRN PLAINS TO
THE MID-MS VLY...
...SYNOPSIS...
THE MID-LVL WAVE LOCATED OVER THE GRT BASIN LATE IN THE WEEKEND WILL
EJECT ACROSS THE CNTRL/SRN PLAINS AS A NEGATIVE-TILT TROUGH ON
MONDAY AS THE NEXT IMPULSE DROPS SEWD TO THE PAC NW. AT THE SFC...A
LEE LOW WILL INTENSIFY OVER ERN CO THEN MOVE ACROSS NRN KS BY MONDAY
EVENING THEN TO SRN IA BY 12Z TUESDAY. A DRYLINE WILL MIX EWD TO
THE S OF THE LOW...REACHING WRN KS AND THE TX/OK BORDER AREA BY
EARLY AFTN MONDAY...THEN INTO CNTRL KS AND WRN OK BY EVENING. TO
THE E...A WRMFNT WILL CONTINUE TO DEVELOP NWD INTO THE MID-MS VLY.
...CNTRL/SRN PLAINS TO THE MID-MS VLY...
MONDAY STILL HAS THE POTENTIAL TO BE AN ACTIVE WEATHER DAY WITH
STRONG TORNADOES AND VERY LARGE HAIL POSSIBLE...PARTICULARLY OVER
CNTRL/SCNTRL KS AND EXTREME NWRN/NCNTRL OK.
BANDS/CLUSTERS OF ELEVATED TSTMS ARE EXPECTED TO BE ONGOING EARLY
MONDAY ACROSS PORTIONS OF ERN KS/OK OWING TO A ROBUST WAA REGIME
WITHIN A BROAD 45-50 KT SSWLY LLJ. THIS ACTIVITY MAY PROVE
PROBLEMATIC FOR A NWD EXPANSION OF THE WARM SECTOR MONDAY AFTN AND
THIS UNCERTAINTY WAS THE PRIMARY REASON FOR NOT UPGRADING TO A MDT
RISK.
CONFIDENCE REMAINS SUFFICIENTLY HIGH...HOWEVER...IN THE RETURN OF
MID/UPR 60S BOUNDARY LAYER DEW POINTS E OF THE DRYLINE/TRIPLE POINT
INTO AT LEAST SWRN KS BY AFTN. DRYLINE CIRCULATION WILL DEEPEN WITH
APPROACH OF THE UPR TROUGH BY MID-AFTN AND STRONG HEATING WILL ERODE
CINH FOR TSTM INITIATION...MOSTLY LIKELY IN WRN KS. FARTHER
S...CINH WILL BE STRONGER AND LARGE SCALE FORCING COMPARATIVELY
WEAKER ACROSS WRN OK. BUT...ISOLD STORM DEVELOPMENT CANNOT BE RULED
OUT AS FAR S AS WRN OK/RED RIVER.
EFFECTIVE SHEAR IN EXCESS OF 55 KTS AND THE ORIENTATION OF VECTORS
PERPENDICULAR TO THE DRYLINE WILL STRONGLY SUPPORT SUPERCELLS. FCST
HODOGRAPHS EXHIBIT STRONGLY VEERING LOW-LEVEL WINDS WITH THE
COMPLETE VERTICAL PROFILE SIGNATURES INDICATIVE OF HISTORIC STRONG
TORNADIC CASES. VERY LARGE HAIL WILL ALSO BE POSSIBLE.
AS MENTIONED BEFORE...IT IS UNCLEAR HOW FAR N AND E THE QUALITY WARM
SECTOR WILL EXPAND. THE MAXIMUM TORNADO THREAT MAY REALISTICALLY BE
IN NARROW ZONE ACROSS SCNTRL/CNTRL KS INTO NCNTRL OK BEFORE STORMS
MOVE TOWARD A MORE STABLE LOW-LEVEL ENVIRONMENT. LATER OUTLOOKS CAN
ADDRESS THIS UNCERTAINTY.
OTHERWISE...STORMS WILL LIKELY DEVELOP INTO ONE OR MORE MCS/S AND
DEVELOP/MOVE ENE TOWARD THE MID-MS VLY OVERNIGHT WITH LARGE HAIL THE
PRIMARY THREAT.
Day 2 outlooks
SPC AC 080558
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1258 AM CDT SAT MAY 08 2010
VALID 091200Z - 101200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MID-LVL IMPULSE NEAR 43N/145W AT 05Z IS EXPECTED TO DIG INTO THE GRT
BASIN REGION BY SUNDAY NIGHT. AHEAD OF THIS FEATURE...LWR-AMPLITUDE
WAVES WILL CREST THE ROCKIES AND INTO THE PLAINS THROUGH THE PD. AT
THE SFC...TAIL-END OF THE FRONT MOVING INTO THE GULF COASTAL REGION
NOW WILL REDEVELOP NWD THROUGH CNTRL TX BY SUNDAY NIGHT.
...CNTRL PLAINS...
LARGE-SCALE SLY RETURN FLOW WILL GRADUALLY STRENGTHEN TONIGHT AND
SUNDAY AHEAD OF THE APCHG UPR TROUGH AND BEGIN TO TRANSPORT A RICH
GULF AIR MASS INTO CNTRL/SRN TX. A LEAD IMPULSE WILL LIKELY ENHANCE
ISENTROPIC LIFT/ELEVATED TSTMS OVER PARTS OF OK/N TX AS EARLY AS 12Z
SUNDAY WITH ACTIVITY GRADUALLY SPREADING EWD INTO THE MID-SOUTH
DURING THE AFTN. WRN-FRINGES OF THIS ACTIVITY WILL EXPAND WNW FROM
CNTRL/ERN OK TO CNTRL/ERN KS SUNDAY NIGHT AS THE SSWLY LLJ
INTENSIFIES TO 50 KTS AND CONSIDERABLE MOISTENING OCCURS IN THE
H85-H7 LAYER. STORMS WILL BE ROOTED ATOP A STABLE LAYER...BUT
MUCAPE OF 1000-2000 J/KG AND EFFECTIVE SHEAR AOA 45 KTS WILL BE
SUFFICIENT FOR AT LEAST ISOLD ORGANIZED STORMS WITH LARGE HAIL.
...SW TX...
BOUNDARY LAYER IS EXPECTED TO STRONGLY HEAT OVER THE MARFA/STOCKTON
PLATEAUS SUNDAY AFTN AND AUGMENT DIURNAL AND INCREASINGLY MOIST
UPSLOPE FLOW. ISOLD HIGH-BASED TSTMS WILL BE PSBL OVER THE MTNS BY
LATE AFTN WITH ONE OR TWO CELLS ROOTING INTO THE RICHER MOISTURE
ALONG THE ERN SLOPES IF CINH CAN ERODE SUFFICIENTLY. HAVE ADDED LOW
PROBABILITIES THAT AN ISOLD SUPERCELL MAY EVOLVE WITH PRIMARILY
LARGE HAIL POTENTIAL GIVEN 40 KTS OF WLY VERTICAL SHEAR AND STEEP
MID-LVL LAPSE RATES. ACTIVITY SHOULD WEAKEN BEFORE REACHING THE
TRANSPECOS DURING THE EVENING.
Day 1 outlooks
SPC AC 080559
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT SAT MAY 08 2010
VALID 081200Z - 091200Z
...NO SVR TSTM AREAS FORECAST...
...SERN U.S...
WLY FLOW WILL GRADUALLY INCREASE ACROSS THE SERN U.S. WITHIN BASE OF
EJECTING GREAT LAKES UPPER TROUGH. INTERIOR SFC RIDGING WILL BUILD
ACROSS THE MIDDLE OF THE CONUS FORCING A FAIRLY WELL DEFINED COLD
FRONT AND PRE-FRONTAL WIND SHIFT EAST OF THE APPALACHIANS EARLY IN
THE PERIOD. ALTHOUGH WINDS WILL VEER CONSIDERABLY ACROSS GA AND SC
IT APPEARS SFC DEW POINTS SHOULD HOLD IN THE 60S AHEAD OF THE FRONT.
PRIOR TO LOW LEVEL MOISTURE BEING SCOURED OFFSHORE...STRONG HEATING
SHOULD FORCE SFC PARCELS TO REACH THEIR CONVECTIVE TEMPERATURES.
IT/S NOT ENTIRELY CLEAR HOW CONVERGENT THIS BOUNDARY WILL BE ACROSS
GA/SC...BUT EARLY MORNING WV IMAGERY SUGGESTS A WEAK
IMPULSE/SHORTWAVE TROUGH MAY BE EMBEDDED WITHIN THE BASE OF THE
BROADER TROUGH OVER LA/MS. SUBSEQUENT EWD MOVEMENT OF THIS FEATURE
WOULD INTERACT WITH TRAILING FRONTAL ZONE ACROSS GA/CAROLINAS DURING
PEAK HEATING. ALTHOUGH SUBTLE...A FEW STRONG OR ISOLATED SEVERE
THUNDERSTORMS COULD DEVELOP DURING THE AFTERNOON HOURS.
HOWEVER...COVERAGE WILL LIKELY BE INSUFFICIENT TO WARRANT A SLIGHT
RISK...THOUGH LARGE HAIL AND LOCALLY DAMAGING WINDS WOULD BE THE
PRIMARY RISKS WITH STRONGER UPDRAFTS.
...NERN U.S...
IMPRESSIVE HEIGHT FALLS WILL OVERSPREAD THE NERN U.S. AHEAD OF
STRONG UPPER TROUGH EARLY IN THE PERIOD. ASSOCIATED SFC COLD FRONT
WILL SURGE INTO THE HUDSON VALLEY BY 16Z WITH A SMALL WARM SECTOR
EXPECTED TO BECOME WEAKLY UNSTABLE ACROSS PORTIONS OF SRN NEW
ENGLAND INTO THE HUDSON VALLEY BY MID DAY. FORECAST SOUNDINGS
SUGGEST A NARROW WINDOW OF OPPORTUNITY WILL EXIST FOR SFC-BASED
CONVECTION ALONG ADVANCING COLD FRONT IF DEW POINTS CAN RISE INTO
THE UPPER 50S WHERE SFC TEMPERATURES WARM INTO THE 60S. ALTHOUGH
DEEP LAYER SHEAR IS QUITE STRONG...INSTABILITY WILL LIKELY PROVE TOO
WEAK TO WARRANT MORE THAN A FEW ROBUST UPDRAFTS CAPABLE OF PRODUCING
GUSTY WINDS.
...ELSEWHERE...
A FEW POCKETS OF THUNDERSTORMS WILL DEVELOP ACROSS HIGHER ELEVATIONS
OF THE CNTRL AND NRN ROCKIES...AS WELL AS THE MOUNTAINS OF NRN CA.
ANOTHER REGION WHERE THUNDERSTORMS MAY DEVELOP WILL BE ACROSS NRN TX
INTO SRN OK AS STRONG WARM ADVECTION DEVELOPS ACROSS THE SRN PLAINS
LATE IN THE PERIOD. MOIST ISENTROPIC ASCENT ATOP A VERY COOL
RETREATING ANTICYCLONE SHOULD ENCOURAGE ELEVATED CONVECTION TOWARD
09/12Z. THIS ACTIVITY WILL LIKELY BE ROOTED NEAR 700MB AND SEVERE
HAIL IS NOT ANTICIPATED.
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