[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 201240
SWODY1
SPC AC 201239

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0739 AM CDT THU JUL 20 2006

VALID 201300Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE MID MS/OH AND TN
VALLEYS AND GREAT LAKES AREA...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN HIGH PLAINS SEWD
INTO CENTRAL PLAINS...

...SYNOPSIS...
A TROUGH WILL BEGIN TO DEEPEN FROM THE NRN/CENTRAL ROCKIES EWD INTO
THE NRN OHIO VALLEY AND NEW ENGLAND AS THE LARGE UPPER RIDGE SHIFTS
WWD AND BEGINS TO BUILD NWD INTO THE PACIFIC NW. EMBEDDED WITHIN
THIS AMPLIFYING TROUGH WILL BE ONE SHORTWAVE TROUGH MOVING THROUGH
THE GREAT LAKES AND ANOTHER DROPPING SEWD FROM THE NRN ROCKIES INTO
THE CENTRAL PLAINS. A COLD FRONT ASSOCIATED WITH THE DEEPENING
TROUGH WILL MOVE EWD AND IS FORECAST TO EXTEND FROM THE EASTERN
GREAT LAKES SWWD INTO MO AND THEN WWD INTO ERN CO BY LATE AFTERNOON.


...MID MS/OH/TN VALLEYS AND GREAT LAKES AREA...
CONVECTIVE EVOLUTION AND SEVERE THREAT TODAY COMPLICATED BY ONGOING
CONVECTION...BUT LARGE AREA OF INSTABILITY AND UNSEASONABLY HOT
TEMPERATURES WITHIN A MOIST BOUNDARY LAYER WILL RESULT IN A LARGE
SLIGHT RISK AREA. CURRENT THINKING IS WEAKENED BOW ECHO IN NRN
IL/IND WILL MOVE SWD DURING THE DAY IN RESPONSE TO WLY LOW LEVEL JET
AND INSTABILITY AXIS THAT CURRENTLY EXTENDS SWD FROM THE SYSTEM.
WELL ORGANIZED COLD POOL/MESO HIGH SHOULD KEEP SYSTEM ORGANIZED
UNTIL THE AIR MASS DESTABILIZES SUFFICIENTLY FOR REINTENSIFICATION
OF THE SYSTEM. ALTHOUGH THE MID LEVEL WINDS/DEEP LAYER SHEAR WILL BE
WEAKER ACROSS THE LOWER OH/TN VALLEY THAN ACROSS THE GREAT LAKES
AREA...STRONG INSTABILITY...STEEP LAPSE RATES AND ORGANIZED OUTFLOW
LIKELY WOULD KEEP THIS SYSTEM SEVERE AT LEAST AS FAR SOUTH AS TN. 

OTHER SEVERE STORMS MAY DEVELOP ALONG FRONT/OUTFLOW BOUNDARIES
THIS AFTERNOON AND EVENING DUE TO STRONG INSTABILITY...MLCAPES
RANGING FROM 3500+ J/KG MID MS VALLEY TO AROUND 1500 J/KG OVER THE
OH VALLEY...AND STRENGTHENING WINDS ALOFT/SHEAR AS HEIGHTS SLOWLY
FALL. GIVEN THE WARM MID LEVEL TEMPERATURES ALOFT...THE PRIMARY
THREAT WILL BE DAMAGING WINDS.

....NRN/CENTRAL HIGH PLAINS...
ESELY BOUNDARY LAYER WINDS BEHIND COLD FRONT WILL MAINTAIN DEWPOINTS
IN THE 50S OVER PARTS OF THE CNTRL/NRN HIGH PLAINS. STEEP LAPSE
RATES ABOVE THE MOIST AXIS WILL CONTRIBUTE TO MODERATE INSTABILITY
THIS AFTERNOON. AS SHORTWAVE TROUGH MOVES SEWD INTO THE
AREA...STORMS ARE EXPECTED TO DEVELOP OVER THE HIGHER TERRAIN.
THOUGH THE WINDS ARE NOT FORECAST TO BE PARTICULARLY STRONG BELOW
500 MB...SELY BOUNDARY LAYER WINDS VEERING TO WLY IN THE LOWER 3KM
WILL RESULT IN SUFFICIENT SHEAR FOR SUPERCELLS. AN ISOLATED TORNADO
OR TWO MAY BE POSSIBLE WHEN THE STORMS FIRST DEVELOP...BUT AS
OUTFLOWS MERGE...STORMS SHOULD ORGANIZE INTO AN MCS AND MOVE SEWD
ALONG THE 850 MB TEMPERATURE GRADIENT AND INTO THE 25 KT LOW LEVEL
JET. SEVERE HAIL WOULD BE THE PRIMARY THREAT EARLY AND THEN
TRANSITION INTO MORE OF A DAMAGING WIND THREAT AS THE SYSTEM 
FORWARD PROPAGATES INTO WRN/CENTRAL NEB AND NRN KS.

...SWRN TX...
UPPER WAVE THAT RESULTED IN SEVERE THUNDERSTORMS FROM AL INTO ERN TX
WED WILL BE MOVING ACROSS SWRN TX DURING THE PERIOD OF MAX HEATING.
ALTHOUGH THE BOUNDARY LAYER WILL NOT BE AS MOIST OR UNSTABLE AS IT
WAS ACROSS THE CENTRAL GULF STATES... INVERTED-V SOUNDINGS SUGGEST
STRONG/BRIEF SEVERE WIND GUSTS ARE POSSIBLE WITH STORMS.

...SRN AZ...
ELY WINDS ARE FORECAST THROUGHOUT MUCH OF THE TROPOSPHERE ACROSS AZ
TODAY. HOWEVER...WATER VAPOR IMAGERY SHOWS DRIER AIR SPREADING IN
FROM NEW MEXICO AND THE CONVECTIVE COVERAGE WAS MOSTLY SUPPRESSED
WITHIN THIS DRIER MID/HIGH LEVEL AIR MASS ON WED. STORMS CURRENTLY
OVER SERN AZ SHOULD SHIFT WWD...BUT MORNING CLOUDS/PCPN SHOULD LIMIT
HEATING/INSTABILITY SOMEWHAT. AS DRIER AIR MOVES IN FROM THE
EAST...ONLY ISOLATED STORMS ARE EXPECTED OVER THE HIGHER TERRAIN OF
SERN AZ THIS AFTERNOON.

..IMY.. 07/20/2006