Wednesday, October 6, 2010

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 061940
SWODY1
SPC AC 061938

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0238 PM CDT WED OCT 06 2010

VALID 062000Z - 071200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF ERN/NRN AZ INTO
SERN UT...

...AZ/UT...

HAVE OPTED TO MAKE MINOR CHANGES TO ONGOING RISK OF SEVERE ACROSS
PARTS OF SWRN UT/NWRN AZ. PROBABILITIES ARE LOWERED ACROSS THIS
REGION WHERE EXTENSIVE CLOUDINESS/PRECIPITATION ARE SUPPRESSING
INSTABILITY.

OTHERWISE...LATEST WV IMAGERY SUGGESTS MID LEVEL SHORTWAVE TROUGH IS
NOW LIFTING NWD ACROSS CNTRL AZ AND IT APPEARS THE MORE SIGNIFICANT
LARGE SCALE ASCENT/MOISTENING WILL BE CONCENTRATED OVER NRN AZ INTO
SERN UT. SFC DATA SUPPORTS THIS WITH 19Z OBSERVATIONS BEGINNING TO
VEER ACROSS THE LOWER DESERTS AND DEW POINTS ARE BEGINNING TO DROP.
18Z SOUNDING AT TUS ALSO DEPICTS THIS TRANSITION WITH ONLY THE
CONTACT LAYER REMAINING MOIST.

RADAR DATA CONTINUES TO INDICATE NUMEROUS THUNDERSTORMS ALONG A
CORRIDOR FROM ERN YAVAPAI COUNTY IN CNTRL AZ...NEWD INTO SERN UT.
LONG-LIVED SUPERCELLS HAVE TRANSITIONED ACROSS THIS REGION WITH
SEVERAL TORNADOES HAVING TOUCHED DOWN SINCE THE EARLY MORNING HOURS.
LATEST THINKING IS THE GREATEST TORNADO POTENTIAL WILL GRADUALLY
SHIFT INTO THE NERN QUARTER OF AZ AND SERN UT OVER THE NEXT SEVERAL
HOURS...PRIMARILY AHEAD OF EJECTING SHORTWAVE TROUGH WHERE LOW LEVEL
SHEAR AND BACKED FLOW WILL BE MAXIMIZED. IT/S NOT ENTIRELY CLEAR
HOW MUCH CONVECTION WILL DEVELOP IN THE WAKE OF THE SHORTWAVE INTO
SERN AZ...BUT VEERING LOW LEVEL FLOW SHOULD SUPPRESS THE TORNADIC
POTENTIAL AS DEW POINTS DROP WITHIN SSWLY BOUNDARY LAYER FLOW.

..DARROW.. 10/06/2010

.PREV DISCUSSION... /ISSUED 1059 AM CDT WED OCT 06 2010/

...SWRN STATES...
CLOSED UPPER LOW OVER SOUTH CENTRAL CA HAS BEEN SLOWLY RETROGRADING
THIS MORNING...THOUGH AMPLIFYING UPPER TROUGH OVER THE PACIFIC
SHOULD GRADUALLY BEGIN TO SHIFT THIS SYSTEM NEWD TONIGHT. WV IMAGERY
SUGGESTS INTENSE VORT LOBE WAS ROTATING NEWD ACROSS SRN AZ AND WILL
SHIFT NNEWD ACROSS AZ THROUGH THE DAY. AHEAD OF THIS FEATURE...VERY
STRONG UPPER LEVEL DIFFLUENCE/ DIVERGENCE SHOULD AID IN MORNING
SEVERE STORMS OVER NRN/CENTRAL AZ SPREADING/DEVELOPING EWD AND NWD
THROUGH THE DAY. STORMS ARE MOST LIKELY TO EXPAND INTO SRN UT THIS
MORNING AND DEVELOP IN ERN AZ SINCE STORM UPDRAFTS ARE ABLE TO
DEVELOP ABOVE CAPPING INVERSION...EVIDENT ON MORNING TUS SOUNDING
SOUTH OF THE RIM. DEEP LAYER SHEAR WILL BE SUFFICIENT FOR ROTATING
STORMS. THE MOIST BOUNDARY LAYER AND BACKED LOW LEVEL WINDS SHOULD
REMAIN SUPPORTIVE OF TORNADOES FROM NRN AZ NWD INTO SRN UT. FURTHER
EAST...ACROSS ERN AZ/SERN UT/SWRN CO AND NWRN NM...MODELS SUGGEST
MORE MIXING WILL OCCUR AS THE BOUNDARY LAYER WARMS...RESULTING IN A
DRIER BOUNDARY LAYER. IF THIS OCCURS...THE ENVIRONMENT WOULD BE MORE
FAVORABLE FOR STRONG GUSTY WINDS AND SEVERE HAIL.

WHILE STORMS WILL BE A LITTLE SLOWER TO DEVELOP SOUTH OF THE RIM...
THE COMBINATION OF A WARMING AIR MASS AND LARGE SCALE FORCING SHOULD
AID IN STORMS DEVELOPING ACROSS SERN AZ/SWRN NM THIS AFTERNOON.
WHILE HEIGHTS ARE FORECAST TO CHANGE LITTLE...DEEP LAYER SHEAR WILL
STILL SUPPORT SUPERCELLS ACROSS THIS REGION. LOW LEVEL WINDS ARE
FORECAST TO VEER SOMEWHAT...ESPECIALLY FROM TUS WWD...BUT EAST OF
THIS AREA...THE SHEAR AND INSTABILITY MAY SUPPORT A BRIEF TORNADO.

THE SEVERE THREAT SHOULD GRADUALLY END FROM THE SOUTH AND WEST AS
THE UPPER WAVE PASSES THROUGH. HOWEVER...SINCE THE WAVE WILL MOVE
MORE NWD THAN EWD...SEVERE CONVECTION MAY PERSIST IN FAR ERN AZ/WRN
NM AND EVEN SERN UT/WRN CO WELL INTO THE EVENING HOURS.

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