Jan 20-21 SE Severe Storm, SPC Risk Level: Day 1 Slight Risk - Forecasts & OBS Options

[Mid Tn. Man]

DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
1146 AM CST THU JAN 19 2012

VALID 201200Z - 211200Z

...NO SVR TSTM AREAS FORECAST...

CORRECTED FOR NDFD GRAPHIC

...SYNOPSIS...
A PROGRESSIVE LONGWAVE PATTERN WILL PERSIST OVER THE CONUS THROUGH
FRIDAY. WITHIN THIS REGIME...A LOW AMPLITUDE SHORTWAVE TROUGH
CURRENTLY OVER THE PACIFIC NORTHWEST IS EXPECTED TO STEADILY SPREAD
EAST-SOUTHEASTWARD AND AMPLIFY TO A DEGREE AS IT REACHES THE LOWER
MO VALLEY BY LATE FRIDAY. THIS WILL BE AHEAD OF A MORE SUBSTANTIAL
UPPER TROUGH OVER THE EASTERN PACIFIC AND COASTAL PACIFIC
NORTHWEST/BRITISH COLUMBIA.

...TN VALLEY/LOWER OH VALLEY...
AHEAD OF THE AFOREMENTIONED AMPLIFYING SHORTWAVE TROUGH AND EVENTUAL
SOUTHEASTWARD-ADVANCING COLD FRONT...THE PRE-FRONTAL WARM SECTOR
WILL REMAIN CAPPED THE MAJORITY OF THE DAY. BUT BY FRIDAY
NIGHT...INCREASING WARM ADVECTION/CONVERGENCE NEAR THE FRONT...ALONG
WITH THE POSSIBILITY A MODERATELY STRONG/COUPLED UPPER JET
STRUCTURE...SHOULD CONTRIBUTE TO ISOLATED TO SCATTERED CONVECTIVE
DEVELOPMENT ESPECIALLY LATE FRIDAY NIGHT/EARLY SATURDAY ACROSS THE
TN VALLEY AND PORTIONS OF THE LOWER OH VALLEY.

WHILE A DEGREE OF NUMERICAL GUIDANCE STILL EXISTS REGARDING THE
SHORTWAVE TROUGH AND CHARACTERISTICS/SPATIAL EXTENT OF THE WARM
SECTOR...SUFFICIENT EVIDENCE EXISTS TO INTRODUCE LOW SEVERE
PROBABILITIES GIVEN THAT SOME OF THESE STORMS COULD BE ROOTED NEAR
THE SURFACE WITHIN A HIGHLY SHEARED ENVIRONMENT. WITH THE LIKELIHOOD
OF 50S F SURFACE DEWPOINTS AHEAD OF THE FRONT...INCLUDING SOME LOWER
60S F BY THE END OF THE PERIOD ACROSS THE TN VALLEY...STRONG SHEAR
/ACCENTUATED BY A 50 KT LOW LEVEL JET/ MAY YIELD ORGANIZED STORM
MODES WITH THE POSSIBILITY OF SEVERE WIND/HAIL. ADDITIONALLY...A
TORNADO THREAT CANNOT BE RULED OUT ACROSS THE TN VALLEY LATE FRIDAY
NIGHT/EARLY SATURDAY.

..GUYER.. 01/19/2012

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0133 AM CST THU JAN 19 2012

VALID 211200Z - 221200Z

...SYNOPSIS...
A RELATIVELY LOW AMPLITUDE SHORTWAVE TROUGH IS FORECAST TO MOVE FROM
THE LOWER MS VALLEY EWD INTO THE OH/TN VALLEY REGION BY 00Z...AND
CONTINUE INTO THE CAROLINAS OVERNIGHT INTO SUN MORNING. AT THE
SURFACE...LOW PRESSURE IS EXPECTED TO BE CENTERED AROUND CNTRL
KY...WITH PRE FRONTAL TROUGH EXTENDING SWWD INTO THE ARKLATEX. AHEAD
OF THIS TROUGH AND COLD FRONT...SWLY SURFACE FLOW WILL MAINTAIN A
PLUME OF UPPER 50S TO LOWER 60S F DEWPOINTS EMANATING OUT OF THE WRN
GULF OF MEXICO...AND WILL HELP FUEL SCATTERED THUNDERSTORMS...SOME
POSSIBLY SEVERE...FROM ERN MS NEWD INTO ERN TN AND WRN NC.

MEANWHILE...A POWERFUL TROUGH AND JET MAX ARE EXPECTED TO NOSE INTO
THE GREAT BASIN AND FOUR CORNERS DURING THE DAY...CONTINUING EWD
INTO THE CNTRL U.S. BY SUN MORNING. ALTHOUGH LOW PRESSURE WILL
DEEPEN OVERNIGHT WITH THIS SYSTEM...THE AIR MASS WILL BE DRY AS THE
PREVIOUS SYSTEM WILL HAVE CLEARED OUT THE LOW LEVEL MOISTURE WITH A
COLD FRONT.

...CNTRL GULF COAST STATES INTO THE SRN APPALACHIANS...
AHEAD OF THE COLD FRONT...FORECAST SOUNDINGS INDICATE THAT
INSTABILITY MAY BE SUFFICIENT FOR STRONG TO POSSIBLY SEVERE
THUNDERSTORMS GIVEN THE FAVORABLY LONG HODOGRAPHS...ESPECIALLY FROM
MS INTO AL AND NRN GA. INSTABILITY WILL DROP OFF FARTHER N NEAR THE
PRIMARY SURFACE LOW OVER ERN KY/WRN VA...BUT STRONGER FORCING HERE
MAY COMPENSATE FOR LACK OF INSTABILITY TO PRODUCE LOCALLY STRONG TO
SEVERE WIND GUSTS. MODELS SHOW DIFFERING DEGREES OF
INSTABILITY...WITH THE OPERATIONAL NAM SHOWING THE MOST INSTABILITY.
THE NAMKF AND GFS BOTH INDICATE THERE MAY BE PROBLEMS WITH WARM MID
LEVEL TEMPERATURES SOUTH OF THE JET CORE. THEREFORE...WILL ONLY
OUTLOOK ISOLATED SEVERE WITH LOW PROBABILITIES AT THIS TIME.


DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0340 AM CST THU JAN 19 2012

VALID 221200Z - 271200Z

...DISCUSSION...
MODELS AGREE THERE WILL BE A STRONG UPPER TROUGH WITH 100 KT MID
LEVEL SPEED MAX OVER THE CNTRL PLAINS SUN MORNING/D4...MOVING EWD
DURING THE DAY AFFECTING THE MID TO LOWER MS VALLEY REGION. SPEED
DIFFERENCES EXIST BETWEEN THE MODELS...WITH THE ECMWF MORE AMPLIFIED
AND THUS SLOWER THAN THE GFS. REGARDLESS OF WHICH SOLUTION IS MORE
ACCURATE...MOISTURE AND INSTABILITY WILL BE THE LIMITING FACTOR ON
D4. DUE TO THE PREVIOUS DAYS COLD FRONT...MOISTURE WILL BE SHUNTED
SWD A BIT...AND...THE RAPID RETURN NWD WILL LIKELY RESULT IN
WIDESPREAD STRATUS BENEATH THE CAPPING INVERSION. SO DESPITE A
FAVORABLE SYNOPTIC PATTERN...THERE MAY BE FEW STORMS. WITH THESE
UNCERTAINTIES IN MIND...WILL DEFER ANY POTENTIAL SEVERE PROBS TO
LATER OUTLOOKS.

This post has been edited by Mid Tn. Man: Jan 20 2012, 04:43 PM

[Mid Tn. Man]

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0653 AM CST FRI JAN 20 2012

VALID 201300Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LWR MS AND TN VLYS
INTO THE SRN APPALACHIANS...

...SYNOPSIS...
PATTERN WILL REMAIN FAIRLY ZONAL OVER MOST OF THE LWR 48 THIS
PERIOD...DOWNSTREAM FROM PROGRESSIVE/HIGHER AMPLITUDE TROUGH IN THE
E PACIFIC. THE PACIFIC TROUGH WILL APPROACH THE CA/ORE CST EARLY
SAT. WELL IN ADVANCE OF THE PACIFIC SYSTEM...LOW-AMPLITUDE IMPULSE
NOW OVER UT SHOULD MOVE RAPIDLY E/SE TO THE CNTRL HI PLNS THIS
AFTN...AND INTO OZARKS SAT MORNING...SOMEWHAT AMPLIFYING IN THE
PROCESS. THIS SHOULD INDUCE WEAK CYCLOGENESIS ALONG FRONT NOW
STALLING OVER THE TN AND LWR MS VLYS. THE LOW SHOULD REACH E TN BY
12Z SAT AS THE TRAILING...WRN PART OF THE FRONT ACCELERATES SE
ACROSS THE LWR MS VLY/ARKLATEX.

...LWR MS/TN VLY TO SRN APPALACHIANS TODAY THROUGH EARLY SAT...
WARM SECTOR OVER THE LWR MS AND TN VLYS SHOULD REMAIN CAPPED TO DEEP
CONVECTIVE DEVELOPMENT TODAY AS THE MID LVLS REMAIN RELATIVELY WARM
/MINUS 12 TO MINUS 14C AT 500 MB/ AND UPR LVL FORCING WEAK. BUT BY
THIS EVE...CONVERGENCE ALONG AFOREMENTIONED FRONT AND PERSISTENT LOW
LVL WAA/MOISTURE TRANSPORT SHOULD YIELD INCREASING SHOWER/TSTM
DEVELOPMENT FROM PARTS OF AL NWD INTO MIDDLE TN. A SEPARATE BAND OF
STORMS MAY FORM LATER TNGT THROUGH EARLY SAT FROM FAR ERN AR AND NRN
MS NEWD INTO ERN TN...ERN KY...AND N GA AS LARGE SCALE ASCENT
INCREASES WITH APPROACH OF CNTRL PLNS UPR IMPULSE.

THE DEGREE OF DESTABILIZATION ACROSS THE LWR MS/TN VLY REGION
REMAINS IN QUESTION. NEVERTHELESS... SFC AND STLT DATA SHOW
PRESENCE OF SEASONABLY RICH MOISTURE OVER THE NWRN AND N CNTRL GULF
AND ADJACENT PORTIONS OF E TX...LA...AND MS....WHERE SFC DEWPOINTS
ARE IN THE 6OS F. THIS AIR COULD SPREAD N/NE INTO SRN/ERN TN AND
MUCH OF AL LATER TODAY/TNGT...BOOSTING SBCAPE TO AOA 500 J/KG.
SIMILAR VALUES OF ELEVATED INSTABILITY COULD EXTEND NE INTO THE SRN
APPALACHIANS EARLY SAT.

MODERATE TO STRONG UNIDIRECTIONAL DEEP W/SWLY FLOW WILL PREVAIL OVER
THE REGION....WITH 700 MB SPEEDS AOA 40 KTS. NEAR-SFC DIRECTIONAL
SHEAR...WHILE NOT LIKELY TO BE GREAT IN MAGNITUDE... SHOULD MAXIMIZE
IN ZONE OF SLIGHTLY BACKED LOW-LVL FLOW ALONG LEADING EDGE OF
MOISTURE GRADIENT...I.E. FROM NRN MS/W TN SE INTO NRN/CNTRL AL.

OVERALL SETUP NOW APPEARS SUFFICIENT TO WARRANT AT LEAST A
CONDITIONAL SLIGHT RISK FOR WIND...ISOLD TORNADOES...AND PERHAPS
MARGINALLY SVR HAIL. THE THREAT SHOULD BEGIN LATE THIS AFTN OR THIS
EVE...AND MAY PERSIST IN SOME FORM THROUGH 06-12Z SAT GIVEN EXPECTED
CONTINUED AMPLIFICATION OF APPROACHING CNTRL PLNS IMPULSE AS
UPSTREAM SYSTEM DEEPENS ALONG THE W CST.

...CNTRL GULF CST/GA/SRN APPALACHIANS TODAY...
ISOLD TO SCTD BOUNDARY LAYER SHOWERS SHOULD PERSIST THROUGH THE DAY
IN LOW LVL WAA ZONE FROM THE CNTRL GULF COAST TO THE SRN
APPALACHIANS. WEAK MID LVL LAPSE RATES AND NEUTRAL TO...AT
BEST...WEAK UPR LVL FORCING FOR ASCENT SHOULD LIMIT CHARGE
SEPARATION AND THE LIKELIHOOD FOR TSTMS/SVR WEATHER OVER THE REGION.

[Mid Tn. Man]

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1255 AM CST FRI JAN 20 2012

VALID 211200Z - 221200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
WHILE A RELATIVELY WEAK/POSITIVELY TILTED MID-LEVEL TROUGH CROSSES
THE ERN U.S. THIS PERIOD...A MUCH LARGER TROUGH MOVING ONSHORE FROM
THE ERN PACIFIC EARLY IS PROGGED TO ADVANCE ACROSS THE ROCKIES AND
EVENTUALLY APPROACH THE PLAINS.

AT THE SURFACE...A WEAK LOW INVOF THE CENTRAL APPALACHIANS SHOULD
MOVE/REDEVELOP QUICKLY OFF THE MID-ATLANTIC COAST AS THE MID-LEVEL
SHORT-WAVE TROUGH ADVANCES...WHILE A COLD FRONT TRAILING WSWWD
ACROSS THE CAROLINAS AND INTO THE SOUTHEAST PROVIDES A FOCUS FOR
CONVECTIVE WEATHER. MEANWHILE...A STRONGER FRONT ASSOCIATED WITH
THE LARGER WRN U.S. UPPER TROUGH WILL CROSS THE ROCKIES AND EMERGE
INTO THE NRN AND CENTRAL PLAINS OVERNIGHT.

...THE SOUTHEAST...
SHOWERS AND PERHAPS A FEW THUNDERSTORMS SHOULD BE ONGOING ALONG A
SURFACE COLD FRONT LIKELY DRAPED ENE-WSW ACROSS THE MID SOUTH/LOWER
MS VALLEY REGION. AS THE FRONT PROGRESSES SLOWLY SEWD WITH
TIME...ASSOCIATED CONVECTION SHOULD ENCOUNTER A SLIGHTLY MORE MOIST
-- AND THUS UNSTABLE AIRMASS...SUPPORTING CONTINUED SHOWERS AND
STORMS ALONG THE FRONT. WEAK LAPSE RATES ALOFT WILL LIMIT OVERALL
DESTABILIZATION POTENTIAL...AND LIKEWISE HINDER MORE ROBUST SEVERE
POTENTIAL. STILL...WITH A HIGHER THETA-E BOUNDARY LAYER SPREADING
NWD ACROSS THE GULF COAST STATES AND INTO THE CAROLINAS AHEAD OF THE
FRONT AND SHEAR SUFFICIENT FOR ORGANIZED UPDRAFTS...OVERALL SETUP
SUGGESTS CONTINUATION OF LOW SEVERE WEATHER PROBABILITY /MAINLY IN
THE FORM OF DAMAGING WINDS/ THIS FORECAST.

[Hertz]

This storm's got a good moisture feed and nice wind field. IF storms develop, I can't see why there wouldn't be supercells, or even a QLCS/squall line, and there's really no guidance that's dry so I'd be surprised to see no watches or an outlook bust especially after cases of unanticipated watches earlier this week. Looking at instability parameters I think the slight risk however should be shifted 100-200 miles SWD, mainly on the northern end but possibly the southern end as well. That would better match HM's severe weather map he put out this morning, and seems more sensible because the northern half of TN doesn't look to receive the full influx of the warm moist air. That's more southern TN then down south into the Gulf states and therefore it only makes sense that's where the more instense storms will develop.

[Hertz]

Also to note, this event really only looks to go through the 21st, but another separate system with a track further north is progged for the 22nd-23rd. I see severe weather again with this system and extending further north. Possibly make this thread Jan 20-21 and make a Jan 22-23 thread to include the SE but also parts of the Midwest (especially eastern midwest) which should not get severe weather from the current storm.

[Mid Tn. Man]

DAY 3 CONVECTIVE OUTLOOK AMEND 1
NWS STORM PREDICTION CENTER NORMAN OK
0136 PM CST FRI JAN 20 2012

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE LOWER
MS/OH VALLEYS ACROSS THE TN VALLEY AND CNTRL GULF STATES...

AMENDED FOR ADDITION OF SLIGHT RISK AREA

...SYNOPSIS AND FORECAST...

20/12Z NAM GUIDANCE HAS NOW BECOME ALIGNED WITH THE GFS AND ECMWF
WHICH HAVE MORE CONSISTENTLY INDICATED A MORE INTENSE AND LOWER
LATITUDE SHORT-WAVE TROUGH WHICH IS FORECAST TO BECOME NEGATIVELY
TILTED ACROSS THE MID/LOWER MS VALLEY INTO OH VALLEY SUNDAY NIGHT
INTO MONDAY MORNING. AS MENTIONED IN PREVIOUS OUTLOOK...COLD FRONT
WHICH WILL MOVE INTO GULF COAST REGION DURING THE D1/D2 PERIOD WILL
LIKELY WEAKEN...RESULTING IN THE MAINTENANCE OF A MOIST/UNSTABLE AIR
MASS ALONG THE GULF COAST AND SHELF WATERS.

GIVEN THE MORE SRN TRACK OF THE STRONG MIDLEVEL TROUGH...CONFIDENCE
IS INCREASING THAT THE NWD-RETURNING WARM SECTOR WILL COINCIDE WITH
STEEPENING MIDLEVEL LAPSE RATES...STRENGTHENING FORCING FOR ASCENT
AND VERTICAL SHEAR...AND A CATEGORICAL SLIGHT RISK APPEARS WARRANTED
FOR SUNDAY NIGHT INTO MONDAY MORNING. TORNADOES AND DAMAGING WINDS
WILL BE THE PRIMARY SEVERE WEATHER HAZARDS WITH SUPERCELLS AND LINE
SEGMENTS FORMING ALONG AND AHEAD OF THE COLD FRONT.

[Mid Tn. Man]

Also to note, this event really only looks to go through the 21st, but another separate system with a track further north is progged for the 22nd-23rd. I see severe weather again with this system and extending further north. Possibly make this thread Jan 20-21 and make a Jan 22-23 thread to include the SE but also parts of the Midwest (especially eastern midwest) which should not get severe weather from the current storm.

I changed the date and made the thread a OBS,I'm not sure we're suppose to mix regions so i'll just leave it SE unless a Mod wants to change it,really don't matter to me though.

[Mid Tn. Man]

[Mid Tn. Man]

NATIONAL WEATHER SERVICE NASHVILLE TN
335 PM CST FRI JAN 20 2012

.SHORT TERM (TNGT-SUN NGT)...
WARM FRONT WL CONTINUE TO MOVE SLOWLY NORTH THIS AFTN TO NEAR THE
KENTUCKY STATE LINE THIS EVENING. AREA RADARS SHOW ISO RW-
DEVELOPING IN MID TN WITH WARM AND MOIST SOUTHWEST FLOW ALOFT.

SPC OUTLOOKS MID TN FOR SVR WX TNGT...AS WARM AND MOIST AIR BUILDS
ACROSS THE REGION. MODELS SHOW HIGH LEVELS OF SHEAR NEAR THE GROUND
WITH WARM TEMPS ALOFT. THE SHEAR WL SUPPORT ROTATING CELLS POSSIBLY
IN A BROKEN LINE. THE WARM TEMPS ALOFT ARE EXPECTED TO KEEP THE
COVERAGE OF STRONG TO SEVERE STORMS ISOLATED. THE BETTER CHANCE OF
STORMS WL BE IN THE SOUTH WITH MORE UNSTABLE AIR...SOUTH OF I-40
CORRIDOR ATTM.

THE SEVERE WX CHANCE WL END LATE TNGT WEST OF A HARTSVILLE...TO
NASHVILLE...TO WAYNESBORO LINE BTW 09-10Z. THE RISK OF SVR WX WL
SHIFT SOUTH OF THE PLATEAU BY 12Z.

CLOUDY AND COOL CONDITIONS RETURN SAT. DRY SAT NGT. NEXT SFC LOW
PRES SYS DEVELOPS IN THE SOUTHERN PLAIN ON SUNDAY...WITH MUCH
WARMER TEMPS ACROSS MID TN. MOISTURE WL INCREASE AHEAD OF THE COLD
FRONT SUNDAY NIGHT...WITH ANOTHER CHANCE OF SVR WX ACROSS THE
REGION.

SYSTEM SUNDAY NIGHT HAS MORE INSTAB IN THE MODELS FROM HEATING ON
SUNDAY...AND WL MENTION SOME STORMS MAY BE SEVERE FOR ALL COUNTIES
SUNDAY NIGHT. MAIN THREATS WITH SEVERE WEATHER TNGT AND SUNDAY
NIGHT LOOK TO BE DAMAGING STRAIGHT-LINE WINDS AND ISOLATED
TORNADOES.

[Mid Tn. Man]

FXUS64 KHUN 202120
AFDHUN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HUNTSVILLE AL
320 PM CST FRI JAN 20 2012

.DISCUSSION...
TEMPERATURES ACROSS THE TENNESSEE VALLEY ARE CURRENTLY IN THE UPPER
50S TO LOWER 60S...WITH PATCHY DRIZZLE/LIGHT SHOWERS NOTED ON AREA
RADARS. A STATIONARY FRONT IS DRAPED WEST TO EAST ACROSS THE AL/TN
LINE IN THE NORTHERN SECTION OF THE CWA...WITH A SFC LOW CENTERED IN
SRN OK. A DRYLINE EXTENDS SOUTH AND WEST FROM THERE INTO EAST CENTRAL
TEXAS THIS AFTERNOON. IN THE UPPER LEVELS...A LOW WAS ROTATING ACROSS
NRN CANADA WITH ONE SHORTWAVE SPRAWLED ACROSS THE CENTRAL CONUS...AND
ANOTHER U/L SYSTEM APPROACHING THE WEST COAST.

QUITE AN ACTIVE WEATHER PATTERN IS EXPECTED OVER THE NEXT 24-48 HOURS
FOR THE TENNESSEE VALLEY...WITH TWO ROUNDS OF HEAVY RAINFALL AND
STRONG /TO POSSIBLY SEVERE/ THUNDERSTORMS.

OVERNIGHT TONIGHT...THE FIRST OF THESE TWO SYSTEMS WILL IMPACT THE
REGION. AS SFC LOW RIDES ALONG THE WARM FRONT...AND THE SLOW-MOVING
COLD FRONT TO THE WEST MEANDERS EASTWARD...SHOWERS AND THUNDERSTORMS
WILL DEVELOP ALONG AND AHEAD OF THE FRONT. WITH GULF MOISTURE SURGING
NORTHWARD...DEWPOINTS WILL CREEP INTO THE LOWER 60S OVERNIGHT TONIGHT
INTO SATURDAY MORNING. MOST MODELS /MINUS THE NAM/ FAVOR A TIMEFRAME
OF 06-12Z SATURDAY...WITH THE NAM HOLDING OFF ABOUT 6 HOURS /12-18Z/.
FOR NOW...WILL SIDE WITH THE CONSENSUS AND PORTRAY THE BIGGEST THREAT
BETWEEN MIDNIGHT AND DAYBREAK SATURDAY MORNING FOR MOST OF THE
AREA...LINGERING FOR A FEW MORE HOURS IN THE SERN PORTIONS OF THE
CWA. DAMAGING WINDS AND HEAVY RAINFALL WILL BE THE PRIMARY THREATS
WITH THIS ROUND OF ACTIVITY.

SOUNDINGS SHOW SHEAR INCREASING BY MIDNIGHT WITH HELICITIES IN THE
300-400 M2/S2 RANGE. CAPE OVERNIGHT /ACCORDING TO THE GFS AND NAM
BUFR SOUNDINGS/ WILL APPROACH 1400 J/KG. SOUNDINGS ARE ONLY SATURATED
FROM ABOUT 750MB DOWNWARD...WITH AMPLE MID-LEVEL DRY AIR ALOFT. 850MB
WINDS OF 45-50KTS MIXING DOWN TO THE SFC WILL POSE A DAMAGING WIND
THREAT OVERNIGHT. THE THREAT FOR HAIL AND AN ISOLATED TORNADO IS LOW
TONIGHT. IN ADDITION...WITH THE ORIENTATION OF THE FRONT FROM SW TO
NE /AND THE EXPECTED SLOW MOVEMENT TONIGHT/ WILL LEAD TO FLASH
FLOODING CONCERNS. PWATS APPROACH 1.4"...AND WITH WINDS BECOMING
ORIENTED PARALLEL WITH THE FRONT AS IT PASSES...CELL TRAINING IS A
BIG CONCERN. GIVEN HIGH SOIL MOISTURE CONTENT FROM RECENT HEAVY
RAINFALL...WE HAVE ISSUED A FLASH FLOOD WATCH EFFECTIVE FROM 10PM
TONIGHT THROUGH 10AM SATURDAY MORNING. 1-3 INCHES OF RAINFALL IS
EXPECTED THROUGH SATURDAY MORNING...WITH ISOLATED HIGHER AMOUNTS.
/PLEASE REFER TO THE HYDROLOGY SECTION BELOW FOR MORE SPECIFIC
DETAILS/.

GFS/SREF/CANADIAN MODELS PROG A FRONTAL PASSAGE AROUND 12Z IN NW
AL...15Z IN HUNTSVILLE...AND AROUND 18Z IN NE AL. LINGERING SHOWERS
MAY BE POSSIBLE THROUGH SATURDAY NIGHT...BUT A BRIEF BREAK IS
EXPECTED SATURDAY NIGHT INTO SUNDAY AS WE GET READY FOR ROUND 2.

MUCH OF SUNDAY WILL BE RELATIVELY UNEVENTFUL WEATHER-WISE AS THE NEXT
WEATHERMAKER APPROACHES THE AREA FROM THE WEST. THIS UPPER LEVEL
SYSTEM IS CONSIDERABLY STRONGER /AND UNUSUALLY STRONG FOR THIS TIME
OF YEAR/...AND WILL PROVIDE THE AREA WITH THE SECOND AND FINAL ROUND
OF STRONG TO SEVERE STORMS THIS WEEKEND. SHOWERS WILL BE POSSIBLE
ACROSS THE AREA SUNDAY MORNING AND AFTERNOON AS A STRONG COLD FRONT
NEARS THE REGION LATE SUNDAY EVENING. A WIND ADVISORY MAY BE NEEDED
SUNDAY AS THE SYSTEM APPROACHES AND THE PRESSURE GRADIENT TIGHTENS
ACROSS THE AREA. 850MB WINDS ~60KTS WILL TRANSLATE TO A DAMAGING
WIND THREAT SUNDAY NIGHT INTO MONDAY...ALONG WITH HELICITIES BETWEEN
300-500M2/S2. HODOGRAPHS SHOW AMPLE LOW LEVEL SHEAR IN PLACE...
TRANSLATING TO A HIGHER TORNADO THREAT THAN THE FIRST ROUND. MOST
LIKELY...A QLCS WILL SWEEP ACROSS THE AREA OVERNIGHT SUNDAY INTO
MONDAY...WITH STRONG TO SEVERE STORMS POSSIBLE AHEAD OF THE LINE OF
STORMS. SPC HAS A SLIGHT RISK OUTLOOKED FOR THE ENTIRE AREA DURING
THIS TIME. DAMAGING WINDS AND LARGE HAIL WILL BE THE PRIMARY
THREAT...WITH TORNADOES BEING THE SECOND THREAT. HEAVY RAINFALL WILL
LIKELY NOT BE AN ISSUE DUE TO THE QUICK PACE OF THE SYSTEM...BUT
DEPENDING ON EXACTLY HOW MUCH RAIN FALLS TONIGHT...ANY ADDITIONAL
RAINFALL WILL ONLY AGGRAVATE ONGOING FLOODING CONCERNS.

[Mid Tn. Man]

NATIONAL WEATHER SERVICE MEMPHIS TN
250 PM CST FRI JAN 20 2012

.DISCUSSION...

NORTHWARD MOVING WARM FRONT WAS LOCATED RIGHT OVER THE MEMPHIS
METRO AS OF 2PM. TO THE SOUTH BREAKS IN THE STRATUS HAS ALLOWED
TEMPERATURES TO JUMP TO NEAR 70 IN COAHOMA...TALLAHATCHIE AND
YALOBUSHA COUNTIES IN MISSISSIPPI...WITH DEWPOINTS IN THE LOW 60S.
TO THE NORTH OF THE BOUNDARY TEMPERATURES ARE STILL HANGING NEAR
40 DEGREES IN CLAY COUNTY ARKANSAS. A FEW LIGHT RETURNS FROM WAA
SHOWERS WERE SEEN ON RADAR ACROSS NORTHEAST MISSISSIPPI AND WEST
TENNESSEE.

FOR TONIGHT AND SATURDAY...THE WARM FRONT WILL CONTINUE TO MOVE
NORTH AND BECOME SITUATED FROM ABOUT A WYNNE ARKANSAS TO
HUNTINGDON TENNESSEE LINE THIS EVENING...AS A SFC LOW CURRENTLY IN
THE RED RIVER VALLEY RIDES ALONG THE FRONT OVERNIGHT SHOWERS AND
THUNDERSTORMS WILL BECOME MORE SCATTERED. DURING THIS TIME A
SOUTHWESTERLY LLJ WILL INCREASE TO 45 KTS AHEAD OF THE LOW.
THE THREAT FOR A STRONG OR SEVERE STORM REMAINS POSSIBLE MAINLY
AFTER 10PM ALONG AND SOUTH OF INTERSTATE FORTY AS THE FRONT
BEGINS TRACKING SOUTH. THIS IS ALSO THE SAME TIME THAT THE CURRENT
UPPER LEVEL SUPPORT WILL BEGIN AFFECTING THE WARM SECTOR. WILL
MENTION WINDS AND HAIL AS THE GREATEST THREAT IN THE UPCOMING HWO.
IT APPEARS THAT THE PROGGED ISOLATED TORNADO THREAT WOULD BE
BETTER JUST TO THE EAST OF THE CWA. THE FRONT WILL REACH MONROE
COUNTY MISSISSIPPI BY SATURDAY MORNING WITH RAIN CHANCES TAPERING
OFF ACROSS NORTHEAST ARKANSAS...THE BOOTHEEL OF MISSOURI AND
NORTHWEST TENNESSEE. TEMPERATURES ON SATURDAY WILL REMAIN BELOW
NORMAL AS THE CWA WILL STAY TO THE NORTH OF THE FRONT WITH BRISK
NORTH TO NORTHEAST WINDS. SOME BREAKS IN THE CLOUDS ARE
ANTICIPATED LATE IN THE DAY ESPECIALLY ACROSS THE NORTH...BUT ANY
WARMER TEMPERATURES THERE ARE NOT ANTICIPATED.

SUNDAY THROUGH MONDAY...MODELS ARE FAIRLY GOOD AGREEMENT THAT A
MUCH STRONGER SHORTWAVE TROUGH WILL CROSS THE CENTRAL AND SOUTHERN
PLAINS DURING THIS PERIOD SHIFTING FROM A POSITIVE TO NEGATIVE
TILT AS IT CROSSES THE OZARKS. ON THE SURFACE CONDITIONS WILL
START OFF COOL SUNDAY MORNING...HOWEVER AS THE TROUGH APPROACHES
SOUTHERLY LOW LEVEL FLOW WILL INTENSIFY RAPIDLY BY MIDDAY AND
THROUGH THE AFTERNOON...WITH A WARM SECTOR EXPECTED TO REACH THE
LOWER OHIO RIVER VALLEY BY 23/00Z. TEMPERATURES ARE PROGGED TO
CLIMB BACK INTO THE 60S WITH DEWPOINTS ALSO REACHING THE UPPER 50S
TO LOW 60S. THE EURO SHOWS MORE FAVORABLE LAPSE RATES IN THE 6.5
TO 7C RANGE STARTING LATE SUNDAY AFTERNOON THROUGH THE EVENING HOURS.
LOW LEVEL FLOW ALSO APPEARS MORE BACKED AS A 995MB SFC LOW MOVES
NORTHEAST ACROSS MISSOURI. THE ONLY MODEL DIFFERENCES IS THE GFS
AND NAM SHOW A FASTER SYSTEM WITH A LESS INTENSE SFC LOW. THIS
PLACES CONVECTION INITIATION NEAR THE TENNESSEE RIVER VALLEY
INSTEAD OF EURO SOLUTION IN CENTRAL/EASTERN ARKANSAS. HAVE LEANED
TOWARDS THE SLOWER EURO SCENARIO WHICH HAS BEEN MORE CONSISTENT
WITH THIS WEEKEND STORM OVER THE PAST FEW DAYS. THEREFORE A
GREATER THREAT OF SEVERE WEATHER IS LIKELY FOR THE MIDSOUTH LATE
SUNDAY WITH A HIGHER TORNADO POTENTIAL. THE SHORTWAVE WILL
QUICKLY LIFT NORTHEAST OF THE AREA EARLY MONDAY MORNING WITH
BREEZY WEST WINDS AND CLEARING SKIES EXPECTED. HIGHS BEHIND THE
FRONT WILL STILL REMAIN ABOVE NORMAL FOR MID JANUARY WITH READINGS
MAINLY IN THE UPPER 50S TO LOW 60S.

[The Snowman]

Stay safe, everyone.
Significant Tornado Potential

Attached thumbnail(s)

 

[Mid Tn. Man]

Stay safe, everyone.
Significant Tornado Potential

Yup,it's fixing to fire up soon

[Mid Tn. Man]

2K cape just popped up in SE Ark

[Mid Tn. Man]

[Mid Tn. Man]

[Mid Tn. Man]

[Mid Tn. Man]

[Mid Tn. Man]

didnt really pay attention our temps basing on accu has rose 8 degrees

[Mid Tn. Man]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
814 PM CST FRI JAN 20 2012

.UPDATE...AT 01Z QUASI-STATIONARY FRONT EXTENDED FROM JUST NORTH
OF MEMPHIS, TO JUST NORTH OF MKL AND BNA, TO NEAR LAFAYETTE (IN
MACON COUNTY). SURFACE TEMP JUMPED 8 DEGS AT BNA AS FRONT LIFTED
NORTH, BETWEEN 01Z AND 02Z. THIS FRONT MAY STILL WAVER JUST A BIT
FURTHER NORTH OVERNIGHT. HOWEVER, THE MAIN FEATURE WILL BE A
SHORTWAVE DROPPING INTO THE MISSISSIPPI VALLEY LATER TONIGHT,
INCREASING THE COVERAGE OF SHOWERS AND ISOLATED THUNDERSTORMS,
PRODUCING THE POSSIBILITY FOR ISOLATED SEVERE THUNDERSTORMS, AND
KICKING THE FRONT EAST OF NASHVILLE AGAIN SHORTLY AFTER 12Z.

MUCH OF THE MID STATE REMAINS IN A SLIGHT RISK AREA FOR SEVERE
STORMS OVERNIGHT, WITH THE BEST CHANCE EXPECTED TO BE OVER SOUTHERN
AND EASTERN AREAS, IMMEDIATELY ALONG AND AHEAD OF THE FRONT AND THE
INVOF STRONGEST 850MB JET (OF 40-45KTS).

AREA RADARS HAVE SHOWN A GENERAL INCREASE IN THE COVERAGE OF CONVECTIVE
ACTIVITY OVER THE LAST SEVERAL HOURS, ESPECIALLY OVER NORTHERN
ALABAMA AND WEST-CENTRAL MIDDLE TENNESSEE, RIGHT ALONG THE FRONT
ITSELF.

WILL UPDATE ZFP MAINLY TO FOCUS ON MILD OVERNIGHT TEMPERATURES, AND
TO KEEP LIKELIHOOD FOR SHOWERS AND THUNDERSTORMS RUNNING.