SWODY1
SPC AC 040551
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1251 AM CDT MON AUG 04 2008
VALID 041200Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE DAKOTAS INTO THE NRN
OH VALLEY AND PARTS OF LOWER MI...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF SRN LA INTO THE
UPPER TX COAST...
...SYNOPSIS...
A BROADLY CYCLONIC LARGE-SCALE PATTERN OVER THE N-CNTRL STATES WILL
UNDERGO AMPLIFICATION THIS PERIOD AS A SHORT WAVE TROUGH TRANSLATES
EWD FROM THE NRN HIGH PLAINS THROUGH THE UPPER MS VALLEY. THIS
IMPULSE WILL BE ACCOMPANIED BY A BELT OF 45-55 KT FLOW IN THE
MIDLEVELS...INCREASING TO 75-90 KT IN THE UPPER TROPOSPHERE. AT THE
SURFACE...A WEAK...LEAD SURFACE LOW WILL DEVELOP ENEWD FROM NERN IA
INTO LOWER MI WITH A BOUNDARY TRAILING WWD THROUGH THE MID MO VALLEY
TO LOW PRESSURE OVER THE CNTRL HIGH PLAINS. MEANWHILE...A COLD
FRONT ASSOCIATED WITH THE AFOREMENTIONED SHORT WAVE TROUGH WILL PUSH
SEWD THROUGH THE NRN PLAINS AND UPPER MS VALLEY TODAY INTO TONIGHT.
...NRN/CNTRL PLAINS INTO LOWER MI...
A COMPLEX FORECAST EXISTS THIS PERIOD DUE TO ANTICIPATED...ONGOING
MCS/S OVER WI AND THE NRN HIGH PLAINS AT 04/12Z. WHILE LEAD SHORT
WAVE TROUGH /NOW OVER THE UPPER MS VALLEY/ CONTINUES TO LIFT NEWD
ACROSS SRN ONTARIO...AN ATTENDANT WSWLY LLJ WILL MAINTAIN AN INFLUX
OF A MOIST LOW-LEVEL AIR MASS INTO WRN FLANK OF WI MCS. THIS
MOISTURE COMBINED WITH THE EWD ADVECTION OF INCREASINGLY STEEP
MIDLEVEL LAPSE RATES WILL RESULT IN THE DEVELOPMENT OF MODERATE
INSTABILITY BY AFTERNOON /MLCAPES OF 1500-2500 J PER KG/ ACROSS
PARTS OF LOWER MI AND THE WRN/CNTRL OH VALLEY. THIS INSTABILITY IN
CONCERT WITH THE PERSISTENT WAA ALONG NOSE OF LLJ SHOULD EITHER: 1)
MAINTAIN WI MCS MORE SEWD ACROSS LOWER MI PERHAPS INTO NRN PORTIONS
OF IND/OH...OR 2) SUPPORT DEVELOPMENT OF DIURNAL STORMS ALONG
OUTFLOW BOUNDARY REMNANT FROM WI MCS SHOULD IT DECAY. THE PRESENCE
OF 30-35 KT DEEP-LAYER SHEAR WILL PROMOTE ORGANIZED
STORMS...INCLUDING THE POTENTIAL FOR BOWING AND/OR SUPERCELL
STRUCTURES WITH THE PRIMARY SEVERE THREATS BEING DAMAGING WINDS AND
HAIL.
FARTHER W...MORE UNCERTAINTY EXISTS WITH REGARD TO CONVECTIVE
EVOLUTION FROM THE DAKOTAS AND NEB EWD INTO MN/IA. AS MENTIONED
ABOVE...IT APPEARS THAT AN MCS WILL BE ONGOING AT THE ONSET OF THE
FORECAST OVER SERN MT INTO THE WRN DAKOTAS IN ADVANCE OF SHORT WAVE
TROUGH MOVING ACROSS MT. THE RICHEST BOUNDARY LAYER MOISTURE AND
STRONGEST CONVECTIVE INSTABILITY WILL REMAIN CONFINED TO
QUASI-STATIONARY E-W BOUNDARY ACROSS NEB/IA WHERE MLCAPES WILL
APPROACH 2500-4000 J/KG. FARTHER NW...LOW-LEVEL MOISTURE WILL BE
COMPARATIVELY LESS...BUT STEEP LAPSE RATES WILL STILL CONTRIBUTE TO
POCKETS OF MODERATE INSTABILITY ACROSS SD IN ADVANCE OF SECONDARY
FRONTAL SURGE.
DIURNAL TSTM DEVELOPMENT APPEARS MOST LIKELY THIS AFTERNOON ALONG:
1) REMNANT MCS OUTFLOW AND/OR SECONDARY FRONTAL SURGE OVER WRN/CNTRL
SD...AND 2) E-W FRONTAL ZONE OVER NEB/IA. THE COMBINATION OF THE
MODERATE TO STRONG INSTABILITY AND 35-50 KT OF EFFECTIVE BULK SHEAR
SUGGESTS THE POTENTIAL FOR SUPERCELLS WITH THE THREAT FOR A COUPLE
OF TORNADOES...LARGE HAIL AND DAMAGING WINDS. STORMS SHOULD GROW
UPSCALE INTO AN MCS /POSSIBLE BOW ECHO/ TONIGHT WITH A HAIL AND
DAMAGING WIND THREAT SPREADING EWD ACROSS THE REGION. UNCERTAINTY
EXISTS IN THE EVOLUTION AND TRACK OF ANY MCS THAT MAY
EVOLVE...THEREFORE HIGHER SEVERE PROBABILITIES AND A CATEGORICAL
UPGRADE WILL NOT BE INCLUDED IN THIS FORECAST.
...SRN LA INTO THE UPPER TX COAST...
LATEST NHC FORECASTS TAKE T.S. EDOUARD WNWWD ACROSS THE NWRN GULF OF
MEXICO TO NEAR GALVESTON BAY BY TUESDAY MORNING. FORECAST SOUNDINGS
INDICATE THAT A MOIST/UNSTABLE AND MODESTLY SHEARED ENVIRONMENT WILL
EXIST ALONG THE IMMEDIATE COAST WITHIN NRN SEMICIRCLE OF SYSTEM. AS
SUCH...THE POTENTIAL WILL EXIST FOR A FEW ORGANIZED/ROTATING STORMS
TO AFFECT THE IMMEDIATE COAST...ESPECIALLY THIS AFTERNOON WHERE
DIABATIC HEATING WILL EFFECTIVELY BOOST INSTABILITY. A BRIEF
TORNADO OR TWO AND/OR LOCALLY DAMAGING WIND GUSTS APPEAR TO BE THE
PRIMARY THREATS WITH THE MOST INTENSE STORMS.
...AZ/NM...
SCATTERED...DIURNAL STORMS ARE ONCE AGAIN EXPECTED TODAY OVER THE
HIGHER TERRAIN WITHIN A RELATIVELY MOIST AND STEEP LOW-LEVEL LAPSE
RATE ENVIRONMENT. 10-15 KT ELY MIDLEVEL FLOW MAY ALLOW FOR STORMS
TO MOVE/PROPAGATE WWD/SWWD INTO THE LOWER ELEVATIONS WITH THE
POTENTIAL FOR WET MICROBURST ACTIVITY WITH ANY MORE INTENSE STORM
CLUSTERS.
..MEAD/GRAMS.. 08/04/2008
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