Strong to Severe Weather Threat, Saturday, 1/3/15

I need to keep reminding myself that a marginal risk is a see text from back in the day. If you ask me, this whole marginal stuff adds more confusion to an already difficult severe weather risk explanation. I don't even mention the outlooks on air unless they include a slight/moderate/high.

NEW ORLEANS AFD:

AS MENTIONED THE WEATHER WILL BE QUIET TONIGHT BUT THINGS WILL START
TO CHANGE. CLOSED LOW THAT BROUGHT SNOW...YES SNOW TO PORTIONS OF SRN
CA AND LAS VEGAS WILL STOP DIGGING THIS EVNG AND SLOWLY WORK TWRDS
THE DESERT SW AND 4 CORNERS REGION. THIS CUT OFF LOW WILL BE VERY
SLOW TO MOVE FROM THU MORNING THROUGH FRI NIGHT WHEN IT FINALLY
STARTS TO OPEN UP AND DRIVEN OUT BY AN APPROACHING S/W COMING FROM
THE PAC NW. FINALLY BY SAT EVNG THE LOW WILL BE A STRONG OPEN WAVE
MOVING ACROSS THE CNTRL PLAINS AND INTO THE MID MS VALLEY AND
EVENTUALLY ABSORBED IN THE MEAN FLOW AS IT PUSHES TWRDS THE GRT
LAKES. THIS WILL PUT THE REGION UNDER SW FLOW EARLY TOMORROW WHICH
WILL START TO INCREASE THE MOISTURE OVER THE AREA. AT THE SFC HIGH
PRESSURE WILL HOLD STRONG ONE MORE NIGHT BUT WILL SHIFT OFF TO THE
NE THU NIGHT AND THIS WILL ALLOW MOISTURE TO RETURN IN THE LL AS
WELL. BY FRI/FRI NIGHT A WEAK INVERTED TROUGH WILL SET UP ACROSS THE
REGION WITH A WEAK WAVE MOVING OUT OF THE NWRN GULF SAT MORNING AND
INTO AR AND THEN THE MO BOOTHEEL THROUGH THE DAY. THIS WILL
EVENTUALLY DRIVE A COLD FRONT THROUGH THE CWA SAT NIGHT AND EARLY
SUN.

SO WHAT DOES THIS ALL MEAN...WELL TONIGHT LOOK FOR ONLY INCREASING
MID/HI CLOUDS AND THEN AS THE LL MOISTURE SLOWLY INCREASES TOMORROW
WE MAY START TO SEE A FEW LGT SHRA PUSHING IN FROM THE WEST/SW.
DURING THE EVNG HRS THINGS WILL CHANGE. PWS WILL CREEP BACK UP TO
AROUND 1.5 INCHES AND AS THE LIFT INCREASES SRHA AND EVEN A FEW
EMBEDDED TSRA WILL INCREASE IN COVERAGE THROUGH THE NIGHT. ON FRI
THERE WILL LIKELY BE A BREAK AT SOME POINT...PROBABLY IN THE AFTN.
THERE WILL BE SOME INSTABILITY AND A LITTLE MID LVL FLOW TO WORK
WITH THAT COULD ALLOW FOR A FEW STRONG STORMS BUT IF THERE IS SVR
WEATHER IT LOOKS LIKE THE BEST CHANCE WILL BE SAT. ON SAT
INSTABILITY WILL INCREASE AND AS THE OLD CUT OFF LOW CURRENTLY OVER
SRN CA IS LIFTING OUT ACROSS THE SRN/CNTRL PLAINS LIFT WILL INCREASE
AND MID LVL FLOW WILL RAMP UP WITH H5 WINDS APPROACHING 65-70KTS.
COMBINE THAT WITH THE WEAK WAVE MOVING INTO AR AND DEEPENING INTO A
FULL BLOWN SFC LOW WILL NOT HURT THINGS. SHEAR WILL BE IN PLACE AND
THIS IS SETTING UP THE INGREDIENTS FOR A FEW STRONG TO SEVERE STORMS
SAT. AS BOTH THE SFC LOW AND S/W PULL OFF TO THE NE SAT NIGHT THINGS
SHOULD START TO QUIET DOWN. A FEW THINGS WORKING AGAINST SVR WEATHER
CHANCES IS TIMING. WHEN THE BEST LL SHEAR IS IN PLACE THE DEEP LAYER
SHEAR WONT BE QUITE YET AND THE STRONGEST MID LVL FORCING WILL STILL
BE WEST OF THE AREA SO NOT EVERYTHING WILL LINE UP. DEEP LAYER SHEAR
0-6KM BULK SHEAR AROUND 40-50KTS WONT BE SEEN UNTIL CLOSER TO 00Z
SUN. SO WITH THAT WE MAY NOT BE ABLE TO REALIZE THE FULL POTENTIAL
DUE TO TIMING ISSUES. RAIN CHANCES WILL FINALLY COME TO AN END AFTER
THE COLD FRONT PULLS THROUGH DURING THE DAY SUN.

JACKSON:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
339 PM CST THU JAN 1 2015

...WET WEATHER PATTERN INTO FIRST HALF OF WEEKEND...WITH INCREASING
RISK OF STRONG TO SEVERE STORMS AND HEAVY DOWNPOURS ON SATURDAY...

.SHORT TERM...
TONIGHT THROUGH SATURDAY NIGHT...RAIN HAS BECOME WIDESPREAD OVER
MOST OF OUR AREA THIS AFTERNOON WITH THE EXCEPTION OF THE HIGHWAY 98
CORRIDOR. POCKETS OF MODERATE TO HEAVY RAIN ARE OCCURRING OVER THE
NORTHWEST HALF OF THE AREA. TRENDS AND MODELS INDICATE THIS RAIN WILL
CONTINUE FOR AT LEAST SEVERAL MORE HOURS AS ISENTROPIC ASCENT
CONTINUES AHEAD OF LEAD S/WV SHOWN IN WATER VAPOR OVER EASTERN TX
ATTM. MODELS INDICATE A LULL IN THE PRECIPITATION LATER TONIGHT INTO
FRIDAY AS LOW LEVEL VEERS IN WAKE OF INITIAL WAVE. HAVE WENT ALONG
WITH THIS TREND BY LOWERING POPS A BIT DURING THIS TIME FROM CATEGORICAL
VALUES OF EARLIER TONIGHT. WHILE POPS WILL BE LOWER...STILL EXPECT SOME
PRECIPITATION TO CONTINUE AS ISENTROPIC ASCENT OF MOIST AND SOMEHWAT
UNSTABLE GULF AIR CONTINUES ATOP RESIDUAL COOL DOME NEAR SURFACE.
HIGH RESOLUTION MODELS SHOW MORE SHOWERY NATURE TO PRECIPITATION AND
HAVE DEPICTED WEATHER GRIDS ACCORDINGLY.

FURTHER UPTICK IN PRECIPITATION COVERAGE EXPECTED AGAIN LATER FRIDAY
NIGHT INTO EARLY SATURDAY. MODELS DEPICT THIS IN TWO FOCI...ONE OVER
OUR FAR WESTERN AREAS AS MAIN UPPER TROUGH BEGINS TO APPROACH...AND
ANOTHER FARTHER EAST IN AREA OF INCREASING LOW LEVEL WARM AIR
ADVECTION/ISENTROPIC ASCENT OVER EASTERN HALF OF MS. CONSENSUS OF
MODEL POPS CAPTURE THIS SCENARIO PRETTY WELL AND HAVE ACCEPTED.

MAIN TIME PERIOD FOR HAZARDOUS WEATHER POTENTIAL LOOKS TO BE
SAT INTO SAT EVE. MODELS IN AGREEMENT THAT SW CONUS MID/UPPER LEVEL
LOW WILL EJECT THROUGH THE SOUTHERN PLAINS...INCITING DEVELOPING
SURFACE CYCLONE TO OUR NW. UNUSUALLY WARM/MOIST AIRMASS WHICH WILL
HAVE BEEN BUILDING OFFSHORE NEXT 24-36 HOURS WILL SURGE NORTH AS
PRESSURES FALL ACROSS REGION. GFS/EURO AGREE ON 65-70F SURFACE
DEWPOINTS OVERSPREADING MOST OF OUR AREA BY MIDDAY SAT. LAPSE RATES
WILL ACTUALLY BE RELATIVELY ROBUST FOR MID WINTER AS WELL WITH VERTICAL
TOTALS IN THE 27-28C RANGE. THIS WILL SUPPORT MLCAPE VALUES OF 750 TO
1250 J/KG...POTENTIALLY A BIT HIGHER IN ANY AREAS WHICH GET A LITTLE
SUN. LOW AND DEEP LAYER SHEAR WILL BE VERY FAVORABLE FOR SEVERE
WEATHER AS LOW/MID LEVEL JETSTREAKS OVERSPREAD AREA WITH THE EJECTING
TROUGH. ALL THIS SPELLS AN INCREASING RISK FOR SEVERE STORMS SAT...
INCLUDING THE POTENTIAL FOR SOME TORNADOES. MAIN UPPER TROUGH IS
EJECTING WELL TO OUR NW WHICH WILL LIMIT MID LEVEL HEIGHT FALLS THE
FARTHER SOUTH ONE GOES. HOWEVER...IT DOES APPEAR THERE WILL BE AN
OVERLAY OF DECENT HEIGHT FALLS AND FAVORABLE PARAMETER SPACING OVER
THE NW 2/3 OF OUR AREA...AND UPPER JET SUPPORT IS FAVORABLE IN
ENTRANCE REGION OF 150 KT 250 MB JET PULLING THROUGH MID MS VALLEY.
FOR NOW HAVE INCREASED THE AREA GENERALLY ALONG AND JUST NW OF THE
NATCHEZ TRACE TO AN ELEVATED RISK OF SEVERE...AND EXPECT FURTHER
REFINEMENTS WILL BE NEEDED THE CLOSER THE EVENT COMES.

WITH REGARD TO HEAVY RAINFALL POTENTIAL...AS MENTIONED ABOVE MODELS
SUGGEST VERY FAVORABLE UPPER JET SUPPORT FOR ROBUST CONVECTION ACROSS
AREA SAT INTO SAT NIGHT. RIGHT NOW APPEARS AS THOUGH THERE WILL BE
TWO FOCI FOR ORGANIZED HEAVY RAIN PRODUCING STORMS. FIRST WILL BE IN
THE WESTERN AREAS FRI NIGHT THROUGH EARLY SAT AFTERNOON AS UPPER
DIVERGENCE OVERSPREADS AREA JUST EAST OF AN AXIS OF STRONG MOISTURE
TRANSPORT. GFS SHOWS A WEAKNESS IN CORFIDI VECTORS HERE DURING THIS
TIME PERIOD IMPLYING INCREASED RISK OF TRAINING. OF PERHAPS MORE
CONCERN IS AREA OF SURGING SUBTROPICAL AIRMASS WITH 330+K 850 MB
THETA E AND PW VALUES APPROACHING 2 INCHES WHICH ECMWF/GFS SHOW
COMING UP INTO SOUTHERN MS BY SAT AFTERNOON. THIS SETS UP A STRONG
AXIS OF MOISTURE TRANSPORT FROM SC LA THROUGH NE MS WHICH HOLDS IN
PLACE FOR ABOUT 12 HOURS AS UPPER JET SUPPORT OVERSPREADS AREA. THIS
COULD RESULT IN TRAINING OF EFFICIENT RAIN PRODUCING STORMS FOR
SEVERAL HOURS SOMEWHERE ACROSS CENTRAL/ERN MS SAT AFTERNOON AND
EVENING. FOR NOW GIVEN RATHER MESOSCALE NATURE OF THIS POTENTIAL
SETUP WILL JUST LEAVE FLOODING POTENTIAL IN HWO AS LIMITED...BUT WILL
NEED TO MONITOR FOR GREATER RISK AND POSSIBLE FLASH FLOOD WATCH AS
THE EVENT APPROACHES. THERE WILL ALSO BE SOME RISK OF PONDING ISSUES
DUE TO PROLONGED NATURE OF WAVES OF MODERATE TO HEAVY RAIN WITH
EMBEDDED TSRA TONIGHT THROUGH FRIDAY NIGHT AND THIS WILL ALSO BE
MENTIONED IN HWO. GFS AND EURO NOW SHOWING 72 HOUR TOTALS OF 2-4
INCHES OVER MOST OF OUR AREA BY SUNDAY MORNING. /AEG/

MOBILE:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
418 PM CST THU JAN 1 2015

...SHOWERS AND STORMS INCREASE IN COVERAGE FRIDAY THROUGH EARLY
SUNDAY WITH LOCALLY HEAVY RAINFALL POSSIBLE...

...A FEW STRONG TO SEVERE STORMS POSSIBLE SATURDAY AND SATURDAY NIGHT...

.SHORT TERM [TONIGHT THROUGH FRIDAY]...A STALLED SURFACE BOUNDARY
OVER THE NORTHERN GULF WILL PROVIDE THE FOCUS FOR ISENTROPIC
UPGLIDE INDUCED SHOWERS EXPECTED TO SPREAD EAST ACROSS THE FA
TONIGHT. LOOKING AT THE GUIDANCE IS ADVERTISING ABOVE THE
SURFACE...ELEVATED THUNDERSTORMS MIXING IN WELL AFTER SUNRISE
THROUGH FRIDAY. AT THIS POINT...BEST PRECIP COVERAGE WILL BE OVER
NORTHWESTERN ZONES AND POINTS NORTHWEST. WILL HAVE TO KEEP AN EYE ON
THIS AS SIGNIFICANT PRECIP MAY DEEPEN THE COLD POOL THE UPGLIDE IS
WORKING ON AND SHIFT THE BEST UPGLIDE AREAS...THIS PRECIP...FARTHER
SOUTH AND EAST. WITH INCREASING CLOUD COVER AND PRECIP MOVING
IN...HAVE TIGHTENED THE TEMP RANGE FROM SEASONAL. /16

[FRIDAY NIGHT THROUGH SUNDAY]...SOUTHWEST FLOW ALOFT WILL CONTINUE TO
SPREAD ACROSS THE CENTRAL GULF COAST REGION FRIDAY NIGHT AS A
VIGOROUS UPPER LEVEL STORM SYSTEM LIFTS INTO THE VICINITY OF WEST
TEXAS. A WARM FRONT SHOULD MEANWHILE BEGIN TO LIFT NORTHWARD ACROSS
THE FORECAST AREA FROM THE GULF OF MEXICO FRIDAY NIGHT INTO EARLY
SATURDAY MORNING...BRINGING A GRADUAL RISE IN DEWPOINTS INTO THE
LOWER TO MID 60S F ACROSS MUCH OF THE REGION BY 12Z SATURDAY. SHORT
RANGE GUIDANCE HINTS AT AN EMBEDDED SHORTWAVE TROUGH LIFTING
NORTHEASTWARD ACROSS SOUTHEAST MS AND SOUTHWEST AL FRIDAY NIGHT WITH
INCREASING COVERAGE OF RAIN SHOWERS AND PERHAPS ISOLATED THUNDERSTORMS
ESPECIALLY ACROSS SOUTHEAST MS AND SOUTHWEST AL. THOUGH DEEP LAYER
SHEAR INCREASES TO 40-50 KNOTS OVER THE REGION FRIDAY NIGHT...
INSTABILITY LOOKS MARGINAL WITH MLCAPE VALUES GENERALLY LESS THAN 200
J/KG. LIFT WILL BE SUFFICIENT TO INCLUDE LIKELY POPS GENERALLY
NORTHWEST OF I-65 FRIDAY NIGHT...WITH POPS IN THE CHANCE CATEGORY
WITH LIGHTER QPF FARTHER TO THE EAST.

THE UPPER LEVEL LOW WILL LIFT NORTHEASTWARD ACROSS THE CENTRAL PLAINS
BY LATE SATURDAY AFTERNOON BEFORE QUICKLY EJECTING TOWARD THE GREAT
LAKES REGION AND CANADIAN PROVINCES SATURDAY NIGHT INTO SUNDAY. AN
ASSOCIATED SURFACE LOW PRESSURE SYSTEM WILL ORGANIZE FROM THE
NORTHWEST GULF OF MEXICO TO THE LA/AR VICINITY EARLY SATURDAY MORNING
BEFORE LIFTING TOWARD THE GREAT LAKES REGION BY LATE SATURDAY
AFTERNOON. A TRAILING COLD FRONT WILL EXTEND SOUTHWESTWARD ACROSS THE
MISSISSIPPI VALLEY REGION LATE SATURDAY AFTERNOON BEFORE GRADUALLY
ADVANCING EASTWARD ACROSS OUR FORECAST AREA LATE SATURDAY NIGHT INTO
SUNDAY. SYNOPTIC SCALE ASCENT WILL SPREAD FROM THE NORTHWEST GULF
THROUGH MUCH OF LA/MS AND WESTERN AL DURING THE DAY SATURDAY AHEAD OF
THE ORGANIZING AREA OF SURFACE LOW PRESSURE AND ASSOCIATED COLD
FRONT. THE LINEAR MCS WILL CONTINUE ITS EASTWARD PROGRESSION ACROSS
OUR FORECAST AREA SATURDAY NIGHT THEN ACROSS EASTERN AREAS BY EARLY
SUNDAY MORNING. WE HAVE CONTINUED TO TREND POPS CATEGORICAL WITH THE
ADVANCING LINE SATURDAY INTO EARLY SUNDAY. PRECIPITABLE WATER VALUES
LOOK TO INCREASE TO 1.5 TO 1.8 INCHES ACROSS OUR CWFA LATE FRIDAY
INTO EARLY SUNDAY...WHICH WILL FAVOR THE POTENTIAL FOR LOCALLY HEAVY
RAINS. THE LATEST FORECAST CONTINUES TO CALL FOR 1 TO 3 INCHES OF
RAIN WITH LOCALLY HIGHER AMOUNTS. THE HEAVIEST RAINFALL AMOUNTS
CURRENTLY APPEAR TO BE FAVORED ALONG AND NORTHWEST OF I-65. DEEP
LAYER SHEAR VALUES INCREASING TO 50-60 KNOTS...A LOW LEVEL JET OF
35-45 KNOTS...AND MLCAPE VALUES OF 400-800 J/KG WILL BRING A POTENTIAL
OF A FEW STRONG TO SEVERE STORMS SATURDAY AND SATURDAY NIGHT. THERE
STILL REMAINS SOME UNCERTAINTY ON THE AMOUNT OF AVAILABLE INSTABILITY...
SO THE SEVERE RISK REMAINS MARGINAL/LIMITED...BUT WE STILL WILL KEEP
MENTION OF ISOLATED SEVERE STORMS WITH DAMAGING WINDS AND POSSIBLY AN
ISOLATED TORNADO IN THE HWO/GRAPHICS. THE LINE LOOKS TO FINALLY CLEAR
OUR EASTERN AREAS BY AROUND MIDDAY OR EARLY AFTERNOON SUNDAY AND WILL
TAPER POPS INTO SUNDAY AFTERNOON. WE KEPT TEMPERATURES FAIRLY CLOSE
TO THE PREVIOUS FORECAST NUMBERS. /21

&&

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CST FRI JAN 02 2015

VALID 031200Z - 041200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SOUTHEAST LA...SOUTHEAST
MS...AND FAR SOUTHWEST AL...

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT RISK AREA
ACROSS THE LOWER MS VALLEY AND CENTRAL GULF COAST...

...SUMMARY...
ISOLATED SEVERE THUNDERSTORMS WILL BE POSSIBLE SATURDAY ACROSS
SOUTHERN PORTIONS OF LOUISIANA AND MISSISSIPPI...AND EXTREME
SOUTHWEST ALABAMA. DAMAGING WINDS AND A TORNADO THREAT WILL BE THE
PRIMARY SEVERE WEATHER POTENTIAL.

...SYNOPSIS...
MODELS ARE IN FAIRLY GOOD AGREEMENT SHOWING THE STRONGEST FORCING
FOR ASCENT WILL REMAIN NORTH OF THE LOWER MS VALLEY/CENTRAL GULF
COAST SATURDAY...AS A SHORTWAVE TROUGH TRACKS ACROSS NORTH TX/OK/KS
SATURDAY AFTERNOON. THIS FEATURE THEN WILL ACCELERATE NEWD TO THE
LOWER GREAT LAKES SATURDAY NIGHT. A SURFACE LOW WILL TRACK FROM
NEAR THE ARKLATEX REGION AT 12Z SATURDAY NEWD INTO THE MID MS
VALLEY...BEFORE FAIRLY RAPID DEEPENING IS FORECAST AS THIS LOW MOVES
INTO LOWER MI/LAKE HURON LATE SATURDAY NIGHT. A COLD FRONT TRAILING
SWWD FROM THE LOW AND WARM SECTOR EXPECTED INTO THE SLIGHT RISK AREA
WILL BE THE PRIMARY FOCUS REGIONS FOR TSTM DEVELOPMENT THIS PERIOD.
AT 12Z SATURDAY...THE COLD FRONT SHOULD EXTEND FROM SWRN AR TO THE
TX COAST. THIS FRONT WILL ADVANCE E/NEWD ACROSS THE OH/TN AND LOWER
MS VALLEYS...AND SHOULD EXTEND FROM UPPER OH VALLEY TO THE SRN
APPALACHIANS TO NEAR MOBILE BY 12Z SUNDAY.

...LA/MS/WRN AND SWRN AL/FAR WRN FL PANHANDLE...
HEIGHT FALLS WILL REMAIN QUITE WEAK ACROSS SRN LA TO SRN AL AND WRN
FL PANHANDLE AS STRONGER FORCING FOR ASCENT REMAINS NORTH OF THE
SLIGHT AND MARGINAL RISK AREAS...ALONG THE TRACK OF THE SRN PLAINS
SHORTWAVE TROUGH. DESPITE THE LACK OF GREATER FORCING FOR ASCENT
AND GENERALLY WEAK LAPSE RATES...A POLEWARD RETURN OF MOISTURE /PW
OF 1.5-1.75 INCHES AND SURFACE DEW POINTS IN THE MID-UPPER 60S/ IS
EXPECTED ACROSS THE SLIGHT RISK AREA. THIS LATTER FACTOR WILL
SUPPORT MUCAPE OF 500 TO AROUND 1000 J/KG PER NAM/GFS FORECAST
SOUNDINGS.

TSTMS WILL LIKELY BE ONGOING SATURDAY MORNING ALONG THE COLD
FRONT...AND POSSIBLY WITHIN THE WARM SECTOR ACROSS SRN PORTIONS OF
LA/MS. AN INCREASE IN DEEP-LAYER WIND FIELDS...NEARLY PARALLEL TO
THE COLD FRONT...WILL TEND TO RESULT IN LINEAR FORCING FOR A
CONTINUED LINE OF STORMS SPREADING EWD SATURDAY. THE 00Z NAM 4 KM
DID INDICATE THE POTENTIAL FOR A FEW DISCRETE STORMS IN THE WARM
SECTOR...AND GIVEN STRONG DEEP-LAYER AND LOW-LEVEL SHEAR...SUPERCELL
STRUCTURES WILL BE POSSIBLE. DAMAGING WINDS AND A TORNADO THREAT
WILL BE THE PRIMARY SEVERE RISKS...ESPECIALLY ACROSS THE SLIGHT-RISK
AREA WHERE HIGHER MOISTURE/INSTABILITY WILL ENHANCE THIS POTENTIAL.

..PETERS.. 01/02/2015