April/May Pattern Discussion

[Mr Bob]

Looks like a fairly active pattern over the latter part of this week and perhaps early next week particularly for the western side of our region.....Obviously severe is always a short fuse situation but it was most interesting to see SPC start actually using Day 6 severe outlooks (and potentially beyond).

[1234snow]

Tornado Warning in East Kentucky. Looks like a good couplet.

[jaxjagman]

 

 

DAY 2 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   1230 PM CDT WED APR 08 2015

   VALID 091200Z - 101200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS THURSDAY AFTERNOON AND EVENING
   ACROSS PARTS OF SOUTHERN GREAT LAKES REGION AND LOWER OHIO
   VALLEY...SOUTHWARD THROUGH THE OZARK PLATEAU AND ARKLATEX REGION...

   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENH RISK
   AREA...ACROSS THE GREAT LAKES REGION AND OHIO VALLEY...SOUTHWARD
   INTO THE SOUTHEASTERN PLAINS...

   ...THERE IS A MRGL RISK OF SVR TSTMS AS FAR SOUTHEAST AS THE EDWARDS
   PLATEAU AND ADJACENT PORTIONS OF THE RIO GRANDE VALLEY...

   ...SUMMARY...
   SEVERE THUNDERSTORMS ARE LIKELY THURSDAY INTO THURSDAY NIGHT ACROSS
   SOUTHERN PORTIONS OF THE GREAT LAKES REGION...AND MUCH OF THE MIDDLE
   MISSISSIPPI AND OHIO VALLEYS INTO THE SOUTHEASTERN PLAINS.  THIS
   WILL INCLUDE THE RISK FOR DAMAGING WIND GUSTS AND LARGE HAIL.  A
   COUPLE OF STRONG TORNADOES ARE POSSIBLE.

   ...SYNOPSIS...
   A SIGNIFICANT IMPULSE...WITHIN THE SOUTHERN BRANCH OF SPLIT
   WESTERLIES EMERGING FROM THE MID-LATITUDE PACIFIC...IS FORECAST TO
   CONTINUE AN EAST NORTHEASTWARD ACCELERATION OUT OF THE GREAT BASIN
   DURING THIS PERIOD.  THIS FEATURE IS EXPECTED TO REACH THE CENTRAL
   HIGH PLAINS BY 12Z THURSDAY...AND THE UPPER MIDWEST BY THURSDAY
   NIGHT...WHERE/WHEN MODELS SUGGEST THAT IT MAY INCREASINGLY PHASE
   WITH A SIGNIFICANT NORTHERN STREAM IMPULSE.  AS THIS OCCURS...MORE
   SUBSTANTIVE DEEPENING OF AN ASSOCIATED SURFACE CYCLONE...EMERGING
   FROM THE CENTRAL PLAINS...IS EXPECTED TO PROCEED ACROSS AND EAST
   NORTHEAST OF THE GREAT LAKES REGION.

   ALTHOUGH SUBSTANTIVE DEEPENING OF THE LOW IS NOT CURRENTLY FORECAST
   AS IT TRACKS FROM THE MID MISSOURI VALLEY TOWARD LAKE MICHIGAN
   DURING THE DAY THURSDAY...IT STILL IS EXPECTED TO BE AT LEAST
   MODERATELY STRONG WITH LOWEST PRESSURES AT OR BELOW 1000 MB.  A
   TRAILING SURFACE COLD FRONT APPEARS LIKELY TO ADVANCE SOUTHWARD
   THROUGH THE MIDDLE MISSISSIPPI VALLEY AND PORTIONS OF THE OZARK
   PLATEAU AND SOUTHEASTERN PLAINS...WHERE IT WILL GRADUALLY OVERTAKE A
   WELL-DEFINED DRYLINE.  A WARM FRONT EAST OF THE LOW APPEARS LIKELY
   TO ADVANCE NORTHWARD THROUGH THE GREAT LAKES REGION...WHILE COLD AIR
   REMAINS DAMMED TO THE EAST OF MUCH OF THE NORTHERN AND CENTRAL
   APPALACHIANS.

   AIDED BY THE PRESENCE OF MOIST AND POTENTIALLY UNSTABLE AIR IN THE
   WARM SECTOR OF THE CYCLONE...LARGE-SCALE FORCING FOR UPWARD VERTICAL
   MOTION SHOULD BE SUFFICIENT TO SUPPORT WIDESPREAD THUNDERSTORM
   ACTIVITY...FROM THE MISSISSIPPI VALLEY AND SOUTHEASTERN PLAINS INTO
   THE APPALACHIANS...PERHAPS PORTIONS OF THE PIEDMONT TO THE EAST OF
   THE SOUTHERN APPALACHIANS.  IN THE PRESENCE OF MODERATELY
   STRONG...40-50 KT DEEP LAYER MEAN FLOW AND DEEP LAYER SHEAR...A
   NUMBER OF THESE STORMS MAY BECOME SEVERE.  MUCH OF THIS ACTIVITY
   SEEMS LIKELY TO BE FOCUSED ON THE AFOREMENTIONED SURFACE
   BOUNDARIES...PARTICULARLY ALONG THE SOUTHEASTWARD SURGING
   FRONT/DRYLINE ACROSS THE OHIO VALLEY INTO SOUTHEASTERN PLAINS BY
   THURSDAY EVENING.

   ...GREAT LAKES/OHIO VALLEY INTO SOUTHEASTERN PLAINS...
   MODEL OUTPUT IS SUGGESTIVE THAT DEEPER/RICHER BOUNDARY LAYER
   MOISTENING MAY BE CONFINED TO A RELATIVELY NARROW CORRIDOR IN
   ADVANCE OF THE COLD FRONT.  AND CONSIDERABLE CONVECTIVE ACTIVITY MAY
   BE ONGOING IN THE WARM SECTOR ACROSS PARTS OF THE MIDDLE MISSISSIPPI
   AND OHIO VALLEYS AT THE OUTSET OF THE PERIOD.  BY 12Z THURSDAY...IT
   ALSO APPEARS THAT THERE MAY BE CONSIDERABLE STABILIZATION OF THE
   BROAD AREA OF STEEP MID-LEVEL LAPSE RATES NOW PRESENT ACROSS THE
   PLAINS INTO THE VICINITY OF THE APPALACHIANS.  THESE FACTORS...AMONG
   OTHERS...MAY BE LIMITING FACTORS TO A POTENTIALLY MORE SUBSTANTIVE
   SEVERE WEATHER RISK FOR THIS PERIOD.

   STILL...GIVEN THE LARGE-SCALE FORCING AND STRENGTH OF DEEP LAYER
   FLOW/SHEAR...INCLUDING A RATHER BROAD AREA OF 40-50 KT SOUTH
   SOUTHWESTERLY 850 MB FLOW DURING THE DAY...THE ENVIRONMENT WILL BE
   CONDUCIVE TO ORGANIZED CONVECTIVE DEVELOPMENT...INCLUDING
   SUPERCELLS.  AND POCKETS OF STRONGER DESTABILIZATION COULD YIELD
   SCATTERED AREAS WITH POTENTIAL FOR INTENSE SUPERCELLS CAPABLE OF
   PRODUCING A STRONG TORNADO OR TWO...IN ADDITION TO VERY LARGE HAIL.
   IT IS POSSIBLE THAT ONE OF THESE AREAS COULD DEVELOP NEAR THE WARM
   FRONT...IN THE VICINITY OF THE SURFACE LOW...ACROSS PARTS OF
   NORTHERN ILLINOIS...INCLUDING THE CHICAGO METRO AREA...
   DURING THE MIDDAY AND AFTERNOON HOURS.  ANOTHER COULD DEVELOP NEAR
   THE COLD FRONT/DRY LINE INTERSECTION...ACROSS PARTS OF THE OZARK
   PLATEAU AND ARKLATEX REGION DURING THE LATE AFTERNOON AND EVENING.
   HOWEVER...TOO MUCH UNCERTAINTY CURRENTLY EXISTS CONCERNING COVERAGE
   AND AREA TO SUPPORT 10 PERCENT SIGNIFICANT SEVERE WEATHER
   PROBABILITIES AT THE PRESENT TIME.

   OTHERWISE...DAMAGING CONVECTIVE SURFACE GUSTS MAY EVENTUALLY BECOME
   THE MOST PROMINENT SEVERE WEATHER THREAT WITH AN EVOLVING SQUALL
   LINE ALONG/AHEAD OF THE COLD FRONT BY THURSDAY EVENING.

   ..KERR.. 04/08/2015

[LithiaWx]

Yep, big wind threat with a huge squall line, stay frosty tomorrow guys.  It appears my area will be largely spared.

[Olhausen]

I accidentally posted this in the March thread so here it is again.Spc severe outlook for today.

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[Olhausen]

I heard a few thunderstorms around 3 am this morning but other then that it was meh.

[LithiaWx]

Wet week incoming per NWS. I'm starting to believe it looking at the radar.

[jaxjagman]

Wet week incoming per NWS. I'm starting to believe it looking at the radar.

 

Wet indeed,hope we get some rumbles with it.Not very severish look for us around the Valley

[dwagner88]

Ugh. So much drizzle . This is what winter is supposed to be like. Not mid April. I still haven't heard thunder yet this year. I've slept through our only storm this spring.

[Stovepipe]

The GFS is making me nervous for frost in 7 days.  What do you guys think?

[nrgjeff]

Fortunately the Euro keeps it 45+ at night. My gut says near 50. However I just all but declared heating season over so we are now subject to the energy met's jinx, lol!

 

Before that cool front we should hear some thunder over the weekend when the system finally ejects out of Texas. Agree with SPC nothing too interesting attm, but it 5 days out mid-April in Dixie...

[Carvers Gap]

NAO is about to tank...I put even money on the idea that the areas above 5,000' have not seen their last snow.  Ugly, ugly, cold pattern about to unfold in a week or so IMO. 

[Stovepipe]

NAO is about to tank...I put even money on the idea that the areas above 5,000' have not seen their last snow.  Ugly, ugly, cold pattern about to unfold in a week or so IMO. 

 

 

[Carvers Gap]

Bro, I hope I am wrong. But the 12z GFS looked raw for late April and early May. Might have to fire up the woodstove one more time.

[Carvers Gap]

18z GFS looks cold as well. Would have been a killer pattern this winter. As of now, just going to kill my garden.

[John1122]

I stick with my Grandpa's rule about tomato/corn/melons etc for this area. Don't plant them until the leaves make it to the top of the mountain. They've still got about 1000 feet to go here. My area is just now starting to green up. Still bare above me.

[nrgjeff]

Second April weekend without college basketball begs questions on severe weather. SPC Day 3 valid Saturday goes with a Gulf Coast MCS saving the Mid South from any severe threat on Saturday. Just moderate to heavy rain with thunder arcing up through Mississippi into Arkansas, moving into western Tennessee, is forecast. The said Gulf Coast MCS might not rob all the moisture; plenty of moisture is available north. Trouble is that the MCS does ingest the low level jet, leaving nothing much north of itself. I happen to agree with SPC but they did kind of go all in. No marginal for conditional? If the Gulf Coast MCS fails the door is at least cracked open for the Mid South on Saturday.

 

SPC does introduce a Day 4 outlook for the Mid South valid Sunday. While a decent punch is forecast at 500 mb, the profile suffers from veer-back and weak wind fields at low levels. Same problems go up into Illinois. Best fireworks in Memphis remain with Grizzlies hoops. Enjoy!

[dwagner88]

Getting some flash flooding this morning from a slow moving cluster of storms. The thunderless streak is broken.

[1234snow]

Getting some flash flooding this morning from a slow moving cluster of storms. The thunderless streak is broken.

Yeah looks to be a extremely rainy morning in the southern valley. Up to 4 inches has fallen close to Lookout Mountain with more on the way.

[jaxjagman]

 

DAY 3 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   0229 AM CDT FRI APR 17 2015

   VALID 191200Z - 201200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF NE TX...NRN
   LA...AR...SRN MO AND NW MS...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE
   ARKLATEX...LOWER TO MID MS VALLEY AND CNTRL GULF COAST STATES...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
   PLAINS...CNTRL PLAINS...LOWER TO MID MS VALLEY...CNTRL GULF COAST
   STATES...TN VALLEY AND OH VALLEY...

   ...SUMMARY...
   THUNDERSTORMS WITH WIND DAMAGE AND SEVERE HAIL WILL BE POSSIBLE FROM
   EASTERN PARTS OF THE SOUTHERN PLAINS EASTWARD TO THE CENTRAL GULF
   COAST STATES ON SUNDAY AFTERNOON. THUNDERSTORMS WITH WIND DAMAGE
   POTENTIAL WILL ALSO BE POSSIBLE ACROSS THE MID MISSISSIPPI VALLEY
   SUNDAY.

   ...ARKLATEX/LOWER TO MID MS VALLEY...
   A BROAD UPPER-LEVEL TROUGH IS FORECAST TO MOVE EWD ACROSS THE SRN
   AND CNTRL PLAINS ON SUNDAY AS A COLD FRONT ADVANCES QUICKLY EWD INTO
   THE ARKLATEX AND OZARK MOUNTAINS. AHEAD OF THE FRONT...A BROAD WARM
   SECTOR IS FORECAST FROM EAST TX EWD INTO THE CNTRL GULF COAST STATES
   WHERE MODERATE INSTABILITY SHOULD BE IN PLACE BY AFTERNOON. MODEL
   FORECASTS ARE IN FAIRLY GOOD AGREEMENT...DEVELOPING CONVECTION ALONG
   A PRE-FRONTAL TROUGH JUST AHEAD THE FRONT AND MOVING THE CONVECTION
   EWD ACROSS THE ARKLATEX AND MID MS VALLEY SUNDAY AFTERNOON. NAM
   FORECAST SOUNDINGS ALONG THE INSTABILITY AXIS AT 21Z ON SUNDAY FOR
   LITTLE ROCK AR AND SHREVEPORT LA SHOW AN IMPRESSIVE THERMODYNAMIC
   ENVIRONMENT WITH MLCAPE FORECAST TO BE IN THE 3000 TO 4000 J/KG
   RANGE. THIS COMBINED WITH 0-6 KM SHEAR OF 30 TO 40 KT WITH STEEP
   LAPSE RATES SHOULD BE FAVORABLE FOR STRONG UPDRAFTS. SUPERCELLS
   SHOULD BE CAPABLE OF PRODUCING LARGE HAIL AND WIND DAMAGE. AS STORM
   COVERAGE INCREASES DURING THE AFTERNOON...LINEAR DEVELOPMENT MAY
   ALSO OCCUR. VEERED WINDS JUST AHEAD OF THE FRONT WITH UNIDIRECTIONAL
   WIND PROFILES ABOVE 850 MB COULD BE FAVORABLE FOR AN ENHANCED
   WIND-DAMAGE THREAT ESPECIALLY IF A COLD POOL CAN ORGANIZE ACROSS THE
   REGION.

   FURTHER SOUTH ACROSS THE CNTRL GULF COAST AND LOWER MS
   VALLEY...THUNDERSTORM DEVELOPMENT WILL ALSO BE POSSIBLE SUNDAY
   AFTERNOON. HOWEVER...LARGE-SCALE ASCENT SHOULD BE LIMITED KEEPING
   ANY CONVECTIVE DEVELOPMENT ISOLATED IN NATURE AND CONCENTRATED ALONG
   OUTFLOW BOUNDARIES OR ZONES OF LOW-LEVEL CONVERGENCE.
   STILL...DEEP-LAYER SHEAR MAY BE STRONG ENOUGH WHICH COMBINED WITH
   MODERATE INSTABILITY COULD SUPPORT MARGINALLY SEVERE WIND GUSTS
   ACROSS THE REGION.

[jaxjagman]

 

Some nice capes showing up for next Friday on the GFS.0-6km shear is 60-70 kts,hodos look like straight line though and the convection looks a little better today than yesterday.Looks unsettled on the GFS for next Wed through Sunday in the Valley

[Carvers Gap]

Mid-late spring cold will have to be reckoned with several late season frosts(maybe a freeze?) possible according to the 6z GFS. I certainly would not rule out mtn snow. Going to be a shock to the system. This has been on the GFS for several days. Allan Huffman on Twitter provides the graphics. Cold snap for us will range 4-8 below normal. Though the northern Valley will flirt with 8-10 below normal. The Ohio Valley could be 10-12 below normal. With plenty of moisture moving northeast...the Valley is set to enter a very cold, rainy pattern. The mtns above 5,000' are going to be close. Late snows are rarely modeled correctly for the tops of the Smokies where their climate is closer to that of southern Canada. Would have been an awesome winter pattern.

[jaxjagman]

Mid-late spring cold will have to be reckoned with several late season frosts(maybe a freeze?) possible according to the 6z GFS. I certainly would not rule out mtn snow. Going to be a shock to the system. This has been on the GFS for several days. Allan Huffman on Twitter provides the graphics. Cold snap for us will range 4-8 below normal. Though the northern Valley will flirt with 8-10 below normal. The Ohio Valley could be 10-12 below normal. With plenty of moisture moving northeast...the Valley is set to enter a very cold, rainy pattern. The mtns above 5,000' are going to be close. Late snows are rarely modeled correctly for the tops of the Smokies where their climate is closer to that of southern Canada. Would have been an awesome winter pattern.

yup,our severe threat went out the door real quick like,Euro is showing 38 for us next Sun morn

 

[jaxjagman]

 

 

 

DAY 2 CONVECTIVE OUTLOOK 
   NWS STORM PREDICTION CENTER NORMAN OK
   1237 AM CDT SAT APR 18 2015

   VALID 191200Z - 201200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF AR...NRN LA AND
   WCNTRL MS...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SRN
   PLAINS...ARKLATEX...LOWER TO MID MS VALLEY...TN VALLEY AND GULF
   COAST STATES...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PARTS OF THE SRN
   PLAINS...ARKLATEX...LOWER TO MID MS VALLEY...TN VALLEY...GULF COAST
   STATES AND CAROLINAS...

   ...SUMMARY...
   THUNDERSTORMS WITH WIND DAMAGE AND SEVERE HAIL WILL BE POSSIBLE FROM
   EASTERN PARTS OF THE SOUTHERN PLAINS EASTWARD TO THE CENTRAL GULF
   COAST STATES ON SUNDAY AFTERNOON. THUNDERSTORMS WITH WIND-DAMAGE
   POTENTIAL WILL ALSO BE POSSIBLE ACROSS THE MID MISSISSIPPI VALLEY
   SOUTHEASTWARD INTO THE WESTERN CAROLINAS AND EASTERN GULF COAST
   STATES ON SUNDAY.

   ...ARKLATEX/OZARKS/LOWER TO MID MS VALLEY/TN VALLEY...
   AN UPPER-LEVEL TROUGH IS FORECAST TO MOVE ACROSS THE SRN PLAINS ON
   SUNDAY AS A COLD FRONT ADVANCES SEWD INTO THE OZARKS AND ARKLATEX.
   AHEAD OF THE FRONT...SFC DEWPOINTS SHOULD BE IN THE LOWER TO MID 60S
   F ACROSS MUCH OF LA...MS AND SRN AR. AS A RESULT...MODERATE
   INSTABILITY SHOULD BE IN PLACE BY MIDDAY FROM EAST TX EWD ACROSS LA
   AND SRN AR INTO MS. SCATTERED THUNDERSTORM DEVELOPMENT SHOULD TAKE
   PLACE ACROSS THE WARM SECTOR DURING THE AFTERNOON AS A LOW-LEVEL JET
   STRENGTHENS ACROSS THE OZARKS AS IS DEPICTED BY THE GFS SOLUTION. AS
   STORMS INCREASE IN COVERAGE LATE SUNDAY AFTERNOON...THE DEVELOPMENT
   OF AN MCS WILL BE POSSIBLE.

   NAM FORECAST SOUNDINGS AT 00Z/MONDAY FROM NRN LA EWD TO JACKSON MS
   SHOW AN IMPRESSIVE THERMODYNAMIC ENVIRONMENT WITH MLCAPE RANGING
   FROM 2000 TO 3000 J/KG AND STEEP LAPSE RATES FROM THE SFC TO ABOVE
   700 MB. IN ADDITION...0-6 KM SHEAR IS FORECAST TO BE IN THE 45 TO 50
   KT RANGE WHICH SHOULD SUPPORT THE DEVELOPMENT OF SUPERCELLS WITH
   LARGE HAIL. A COUPLE TORNADOES MAY OCCUR WITH THE MORE DOMINANT
   SUPERCELLS LATE SUNDAY AFTERNOON. HOWEVER...A TRANSITION TO LINEAR
   MODE COULD TAKE PLACE AS THE EVENT UNFOLDS WITH THE PRIMARY THREAT
   BECOMING WIND DAMAGE. THIS WOULD ESPECIALLY BE THE CASE IF A COLD
   POOL CAN ORGANIZE ACROSS THE OZARKS AND MOVE SEWD INTO THE LOWER MS
   AND TN VALLEYS. A SEVERE THREAT COULD EXTEND SWWD AS FAR AS SE TX
   BUT CAPPING SHOULD MAKE THE THREAT MORE ISOLATED WITH SWWD EXTENT.

   ...SRN OH VALLEY/SRN APPALACHIANS/WRN CAROLINAS...
   AN UPPER-LEVEL TROUGH IS FORECAST TO MOVE ACROSS THE SRN PLAINS ON
   SUNDAY AS A SFC LOW MOVES NNEWD ACROSS THE OH VALLEY. A BROAD ZONE
   OF STRONGER LOW-LEVEL WINDS IS FORECAST TO BE IN PLACE FROM THE OH
   VALLEY SEWD INTO THE CAROLINAS. AS SFC TEMPS WARM DURING THE
   DAY...ISOLATED TO SCATTERED THUNDERSTORM DEVELOPMENT SHOULD OCCUR.
   FORECAST SOUNDINGS FROM LEXINGTON KY SEWD INTO THE SRN APPALACHIANS
   SC AT 00Z/MONDAY SHOW MLCAPE IN THE 100O T0 1200 J/KG RANGE WITH 0-6
   KM SHEAR OF 40 TO 45 KT. THIS COMBINED WITH UNIDIRECTIONAL WIND
   PROFILES ABOVE THE BOUNDARY LAYER COULD SUPPORT A MARGINAL WIND
   DAMAGE-THREAT WITH CELLS THAT CAN ORGANIZE INTO CLUSTERS AND PERSIST
   THROUGH THE AFTERNOON.

   ..BROYLES.. 04/18/2015

 

[jaxjagman]

 

[jaxjagman]

This is a drastic change and shows how much the GFS sucks mid to long range where we had instability towards next weekend and now we have stable air mass showing

 

 

 

Quite humerous Nashville was in the mid 80's now in the 50's

[Stovepipe]

The storms that have moved through during the past 24 hours have been pretty awesome.  The warned one last night had some stout bursty winds.  The GFS is still trying to suggest cold snaps 7 days away but so far they haven't panned out.  Here in the central valley we're officially past our average final frost date.  I'm getting my confidence back, I think, for getting the rest of my plants in the ground.  Anyone seeing anything in the cards that might make me regret that?

[jaxjagman]

[John1122]

Hello May....

 

[jaxjagman]

Hello May....

 

That would be crazy.I believe the latest measurable snow fall for Nashville was April 28?Not exactly sure,the record site for NOAA is down right now but that's what i recall anyways.