[SWODY2] SWODY2

[SWODY2 at goshenarc.org]

ACUS02 KWNS 210743
SWODY2
SPC AC 210741

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0241 AM CDT FRI MAY 21 2004

VALID 221200Z - 231200Z

THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 35 NE
PBG 25 ENE BML BHB ...CONT... 25 SSW JFK PIT MIE BLV VIH EMP GLD AKO
CYS DGW GCC 50 NNE 81V PHP ANW 40 NW OFK OSC.

GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM SSI AQQ ...CONT... 45
SE GPT LUL CBM MSL BNA BWG OWB PAH POF UNO JLN 40 NNE PNC 50 SSE DRT
...CONT... 45 SW P07 FST DDC LIC DEN LAR RWL RKS EVW EKO WMC 4LW RDM
10 NW DLS 50 ENE BLI ...CONT... 45 NE CTB HVR GDV 55 SSW JMS 50 SSW
DLH ANJ ...CONT... 50 WNW 3B1 45 SSE HUL.

...THERE IS A SLGT RISK OF SVR TSTMS CENTRAL HIGH PLAINS EWD ACROSS
MID-UPPER MS VALLEY...GREAT LAKES...NEW ENGLAND....

...SYNOPSIS...
IN MID-UPPER LEVELS...MEAN WRN TROUGH AND ERN RIDGE PATTERN IS FCST
TO CONTINUE THROUGH DAY-2 PERIOD...BUT WITH SIGNIFICANT SHORTWAVE
ADJUSTMENTS.  WRN STATES TROUGH WILL DEAMPLIFY AS SEVERAL
PERTURBATIONS EJECT NEWD ACROSS CENTRAL/SRN ROCKIES AND
PLAINS...AMIDST BROAD FETCH OF SWLY FLOW.  00Z SHORT-RANGE GUIDANCE
AND 21Z SREF OUTPUT ARE IN STRONG AGREEMENT THAT ONE OR TWO OF THESE
LOWER-AMPLITUDE SHORTWAVE TROUGHS WILL EJECT NEWD OVER CENTRAL/SRN
PLAINS SATURDAY AFTERNOON.  MEANWHILE... PRONOUNCED MID-UPPER
CYCLONE SHOULD EVOLVE OVER PACIFIC NW FROM SPEED MAXIMA NOW DIGGING
SEWD AROUND NERN PERIPHERY OF GULF OF AK RIDGE.

AT SFC...CYCLONE SHOULD BE LOCATED INVOF SRN NE/SRN NEB EARLY IN
PERIOD...ALONG BAROCLINIC ZONE THAT SHOULD SAG SWD INTO KS DURING
DAY.  FARTHER E...SYNOPTIC FRONT SHOULD BE QUASISTATIONARY AND
ALIGNED PARALLEL TO DEEP-TROPOSPHERIC MEAN FLOW...FROM MO/IA BORDER
REGION ENEWD ACROSS SRN/ERN GREAT LAKES AREA AND NEW ENGLAND.  WEAK
FRONTAL-WAVE CYCLONE MAY RIPPLE EWD ACROSS PA/NY/NEW ENGLAND DURING
LATE MORNING/EARLY AFTERNOON.

...GREAT PLAINS TO UPPER MIDWEST...
GREATEST SEVERE PROBABILITIES ARE CONCENTRATED NEAR AND NE OF SFC
LOW -- WHERE COMBINATION OF LIFT...SHEAR AND RELATIVELY WEAK CINH
ARE MOST CONDUCIVE FOR RAPID AFTERNOON DEVELOPMENT.  ONCE
AGAIN...LARGE TO EXTREME BUOYANCY IS LIKELY OVER LOWER MO VALLEY
REGION NEAR FRONTAL ZONE...WITH SFC DEW POINTS UPPER 60S TO LOW 70S
F AND STEEP MIDLEVEL LAPSE RATES CONTRIBUTING TO MLCAPE 3500-4500
J/KG.  VERTICAL SHEAR PROFILES ALONG FRONT WILL FAVOR SUPERCELLS
WITH 40-50 KT DEEP-LAYER SHEAR. SEVERE MCS MAY EVOLVE FROM THIS
ACTIVITY AND MOVE ACROSS MID-UPPER MS VALLEY AFTER DARK.  SOME
SIGNIFICANT SEVERE IS POSSIBLE GIVEN ADEQUATE SHEAR AND SUCH LARGE
INSTABILITY...BUT MESOSCALE UNCERTAINTIES PRECLUDE MORE EMPHATIC
CATEGORICAL RISK ATTM.

POST-FRONTAL UPSLOPE FLOW AND ASSOCIATED MOIST ADVECTION AND ASCENT
MAY CONTRIBUTE TO SEVERE TSTM FORMATION OVER SWRN SD AND ERN
WY...PERHAPS AS FAR S AS NEB PANHANDLE AND AS FAR N AS MT FOOTHILLS.
 THOUGH LOW LEVEL FLOW SHOULD BE RATHER WEAK...STRONGLY CURVED
HODOGRAPHS AND AT LEAST MARGINAL DEEP-LAYER SHEAR WILL SUPPORT
SUPERCELL POTENTIAL.

BECAUSE OF STRONG CAPPING AND POTENTIAL VERY HIGH LCL FOR ANY
CONVECTION THAT DOES FORM...MORE MARGINAL/CONDITIONAL SEVERE
PROBABILITIES EXIST DURING LATE AFTERNOON/EARLY EVENING ALONG
DRYLINE...FROM CENTRAL KS SSWWD ACROSS W TX.  ACTIVITY WOULD BE
STRONGLY TIED TO DIABATIC SFC HEATING AND NOT LONG-LIVED.

...GREAT LAKES STATES TO NEW ENGLAND...
SCATTERED TSTMS IN MCS CLUSTERS ARE POSSIBLE THROUGHOUT
PERIOD...TRACKING EWD TO ESEWD ACROSS THIS SWATH.  THIS INCLUDES
POSSIBILITY THAT SEVERE MCS MAY BE ONGOING AT 22/12Z.  MAIN THREAT
WILL BE DAMAGING WIND. DERECHO EVENT IS POSSIBLE FROM AFTERNOON
ONWARD INTO OVERNIGHT HOURS...HOWEVER MESOSCALE UNCERTAINTIES
PRECLUDE MORE CONCENTRATED CORRIDOR OF PROBABILITIES ATTM.  IN
BETWEEN PRE-EXISTING COMPLEXES AND INVOF SFC FRONTAL ZONE...
AFTERNOON/EVENING DEVELOPMENT IS LIKELY WITH BOWS AND A FEW
SUPERCELLS POSSIBLE.  ASIDE FROM OUTFLOW POOLS...FLOW SHOULD BE
NEARLY UNIDIRECTIONAL IN WARM SECTOR...AMIDST 1500-2000 J/KG
AFTERNOON MLCAPE.

FRONTAL ZONE SHOULD BE MODULATED ON MESOSCALE BY ONE OR MORE OUTFLOW
BOUNDARIES REMAINING FROM DAY 1 AND/OR EARLY MORNING DAY-2 MCS
ACTIVITY.  THIS LENDS SOME UNCERTAINTY TO LATITUDINAL POSITIONING OF
EFFECTIVE FRONT...AND THEREFORE STRENGTH OF MIDLEVEL FLOW AND
DEEP-LAYER SHEAR AVAILABLE TO ASSOCIATED CONVECTION.  IN GENERAL TWO
REGIMES WILL BE MOST SUITABLE FOR BOTH SUPERCELL POTENTIAL AND
SFC-BASED BOW ECHO PROPAGATION --
1. AREA E OF FRONTAL-WAVE LOW WHERE BOUNDARY LAYER FLOW IS BACKED BY
ISALLOBARIC FORCING AND
2. ANY OUTFLOW BOUNDARIES FAVORABLY ALIGNED FOR RIGHT MOTION

...INTERIOR NWRN STATES...
WIDELY SCATTERED TSTMS POSSIBLE DURING AFTERNOON AND EARLY EVENING 
PRIMARILY E OF CASCADES...INCLUDING SNAKE RIVER VALLEY REGION...AS
INSOLATION AND OROGRAPHIC ASCENT WEAKEN CINH.  STRONG LARGE SCALE
COOLING/ASCENT ALOFT...COMBINED WITH SFC DIABATIC HEATING AND 35-50
KT DEEP-LAYER SHEAR...MAY SUPPORT WIND/HAIL NEAR SEVERE LEVELS FROM
A FEW STORMS.  MLCAPE UP TO 500 J/KG POSSIBLE AMIDST 8-9 DEG C/KM
MIDLEVEL LAPSE RATES.

..EDWARDS.. 05/21/2004

...NOTICE...
FOR USERS DECODING THE POINTS PARAGRAPH HEREIN...LATITUDE AND
LONGITUDE POINTS FOR THE CATEGORICAL AND PROBABILISTIC OUTLOOK
GRAPHICS ALSO ARE LOCATED IN A SEPARATE PRODUCT UNDER THE WMO
HEADINGS WUUS01 PTSDY1...WUUS02 PTSDY2...AND WUUS03 PTSDY3.  THE
INCLUSION OF POINTS IN THIS PRODUCT WILL EVENTUALLY BE DISCONTINUED.