SPC MD 1799

Wed, 08 Sep 2010 00:00:04 +0000 UTC

MD 1799 CONCERNING HEAVY RAINFALL FOR PORTIONS CENTRAL/N-CENTRAL/NW TX.

MESOSCALE DISCUSSION 1799
NWS STORM PREDICTION CENTER NORMAN OK
0637 PM CDT TUE SEP 07 2010

AREAS AFFECTED...PORTIONS CENTRAL/N-CENTRAL/NW TX.

CONCERNING...HEAVY RAINFALL 

VALID 072337Z - 080230Z

BROAD PLUMES OF HEAVY RAIN ACCOMPANYING INNER-CORE REGION AND INNER
BANDS OF HERMINE ARE EXPECTED TO CONTINUE SHIFTING NNWWD THEN NWD
ACROSS CENTRAL TX THIS EVENING...IN STEP WITH TRANSLATION OF CYCLONE
CENTER.  THIS AREA OF MOSTLY WARM-CLOUD RAIN ALSO MAY
EXPAND/INTENSITY SOMEWHAT AFTER DARK.  RATES 2-3 INCHES/HOUR ARE
PROBABLE.  LOCAL/BRIEF RATES NEAR 4 INCHES/HOUR CAN OCCUR IN MOST
INTENSE/EMBEDDED WARM-CLOUD CORES AND IN ANY TSTMS.

STRONGLY-DEFINED LOW-LEVEL VORTICITY MAX ASSOCIATED WITH HERMINE
WILL CONTINUE TO SHIFT NNWWD PER NHC PROGS...WITH GREATEST
COVERAGE/INTENSITY OF INNER-REGION CONVECTION REMAINING CONCENTRATED
OVER NERN SEMICIRCLE...NW-NE-SE OF CENTER.  LOW LEVEL CONVERGENCE OF
VERY HIGH PW AIR -- 2.25-2.5 INCHES BASED ON GPS DATA -- WILL
CONTINUE INTO THIS REGION...WITH ADDITIONAL FOCI ALONG BANDS NOW
CROSSING I-35 CORRIDOR IN CENTRAL TX.  TRAINING OF ECHOES ALSO IS
LIKELY IN BANDS THAT WILL EXACERBATE HEAVY RAIN THREAT LOCALLY. 
SLGT NOCTURNAL STABILIZATION/DECOUPLING OF BOUNDARY LAYER ALSO WILL
HELP TO FOCUS LLJ AROUND ERN/NRN PORTION OF INNER CYCLONE
ENVELOPE...WHILE STILL KEEPING EFFECTIVE LIFTED PARCELS ROOTED IN
EXTREMELY MOIST BOUNDARY LAYER.

FOR TORNADO THREAT REF SPC WW 647 VALID UNTIL 01Z AND MESOSCALE
DISCUSSION 1798.  REF HPC EXCESSIVE RAINFALL DISCUSSION FOR OVERVIEW
OF HEAVY RAIN THREAT THROUGH 09/00Z.  REF LATEST NHC ADVISORIES FOR
FCST TRACK/INTENSITY OF HERMINE.

..EDWARDS.. 09/07/2010

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FWD...OUN...EWX...SJT...

LAT...LON   30749902 30959930 31389946 32309946 33469940 33499807
            31959741 31149745 30179757 30899796 30699828 30439855
            30749902