Weather Blog: Storm TALK! Sunday Edition

***** UPDATE *******

2:31pm

Tornado Watch could be issued shortly for west TN

Here is their discussion:

NEXT 1-2 HRS WILL BE MONITORING FOR STORM DEVELOPMENT/SUSTENANCE
   OVER NERN AR AND WRN TN AND A CONDITIONAL RISK FOR ISOLD TORNADOES. 
   IF/ONCE UPDRAFTS BECOME ROOTED IN THE BOUNDARY LAYER...AN ENSUING
   ISOLD TORNADO THREAT WILL LIKELY EXIST.
   
   RECENT VISIBLE SATELLITE IMAGERY SHOWS THINNING HIGHER LEVEL CLOUD
   COVER ACROSS ERN AR EWD INTO NWRN MS AND WRN TN LEADING TO POCKETS
   OF INCREASED HEATING.  IN THE LOW LEVELS...SURFACE TEMPS GENERALLY
   NEAR AND S OF I-40 ARE IN THE LOWER 70S WITH DEWPOINTS RISING INTO
   THE LOWER 60S WITHIN A MOIST PLUME EXTENDING UP THE MS RIVER VALLEY.
   THIS IN TURN IS RESULTING IN 500-1000 J/KG MLCAPE AND A WEAKENED
   CAP.  REPEATED CONVECTIVE ATTEMPTS INVOF THE MS/AR/TN BORDER MAY
   EVENTUALLY BREACH THE REMAINING CAP AND LEADING TO ISOLD-SCTD STORMS
   BY MID AFTERNOON.  THE LAST FEW RUNS OF THE HRRR HAVE SUGGESTED
   SHALLOW CONVECTION NEAR MIDDAY WILL GRADUALLY DEEPEN BY 20Z. 
   IF/ONCE THIS OCCURS...SIZABLE CLOCKWISE CURVED LOW LEVEL HODOGRAPHS
   PER NQA VAD DATA /30 KTS 0-1 KM SHEAR/ WITHIN AN INCREASINGLY
   MOIST/DESTABILIZING BOUNDARY LAYER WILL SUPPORT UPDRAFT ROTATION AND
   AN ATTENDANT TORNADO THREAT.

Here is an update from Kevin's post below..

SPC pretty much has kept the SLIGHT/MODERATE risks in the same spot with the midday update (THIS IS FOR THIS AFTERNOON AND LATE TONIGHT)

Tornado threat has increased some. The blue hatched area means F2-F5's are quite possible.

Straight-line wind threat is also pretty high

Hail threat exists as well.

What I like I about the hail risk map is that it points out what we are facing. 3 threats in reality (with 2 showing up on the hail map)

1) Isolated thunderstorms this afternoon. A few strong storms are possible...so we'll have to watch those carefully as severe storms along warm fronts are possible.

2) Leftovers from the tornado outbreak that develops tonight in AR/TN and heads northeast

3) Potential for another squall line to form right before the cold front pushes through Monday morning/midday.

Here is the new SPC outlook for MONDAY MORNING/AFTERNOON:

Probabilities of severe:

Complicated setup for sure that will be difficult to forecast in advance.

You can see showers and storms already firing along the warm front to our south:

Notice the wind arrows. E/SE locally and then the arrows shift due south near and below the showers/storms. That is how we pick out a warm front. Tempeatures in the 60s/70s south of that front. We will tap into the warm air as the evening arrives and it will be a warm overnight.

The GFS/NAM still..even this close, differ on timing. This impacts mostly the Monday morning/midday threat. If the slower NAM is right...we may see storms fire right over us before heading into east KY. GFS would lessen the threat for this timeframe.

But again, it will all depend on what happens tonight on the setup for tomorrow morning.

Lifted Index from the NAM in the morning has dropped to -6. Which is pretty unstable.

CAPES have also increased to 1500 on the models. Again, plenty for severe storm development.

And look at the 70+kt winds that are flowing overhead. It will be a windy night/Monday event outside of storms. But if the storms tap into this wind energy---wind damage is possible.

Heavy rain threat:

Flood WATCH is in effect for the entire viewing area. The graphic below doesn't have green for our southern counties but NWS plans to add those this afternoon so that everyone will be included.

HPC is already placing a 1-3" potential for the area. While this may cause flash flooding...it is the river flooding that will be more significant. Stay tuned as the event unfolds and have a backup plan if you live near a creek/river that floods often.

So what is the plan?

We need to watch the storms this afternoon with the warm front. Then we need to watch the tornado outbreak unfold to our west/southwest. It will be a long night of tracking storms it appears. We will be watching in the morning/midday timeframe as well to see if we indeed get that squall line.

This could be a very dangerous setup folks that everyone will need to pay attention to...especially since this will be happening when many of you are sleeping. Make sure to have your NOAA weather radios plugged in tonight.

Storm spotters---we will need you tonight. Here is the link for you to log in and file reports to the NWS office. ESPOTTER

Bloggers-- we will need your reports as well when it comes to rain totals and wind speeds or... (hopefully not) damage.

Buckle up..here we go...

Comments

Had a nice downpour here at my house with a rumble of thunder the rain drops were pretty big too a sign that moisture is increasing now.

Posted by: AJ | February 27, 2011 at 02:57 PM

OK, so what does the blue-hatched area on the SPC Monday morning/afternoon outlook mean? We looking at F2 - F5 through out Kentucky??

Posted by: Juice It! | February 27, 2011 at 03:48 PM

No. The blue hatched was on the tornado risk map. The map for Mon only does overall severe risk. they only break it down by tornado/hail/wind on day one outlooks. Good question! BG

Posted by: Brian Goode | February 27, 2011 at 03:53 PM