Post-Christmas severe weather outbreak?

[CrazyC83]

Initiation is the key IMO. CAPE is decent, helicity and shear are insane...I think any supercells that do get going could rapidly be capable of significant tornadoes. But will they get going?

The fact this is a nocturnal event makes it more dangerous.

[6SpeedTA95]

This could ge tpretty interesting. 10% hatched area for tornadoes in my immediate area and right now the dewpoint is 60 at my house with an ambient temp of 77*

[CrazyC83]

I'm guessing initiation is 4-6 hours away.

[6SpeedTA95]

I'm guessing initiation is 4-6 hours away.

Depends on the location. SE OK could see initiation the next 2 or 3 hours. Further north is definately 4 to 6 hours away. This is going to be a dangerous overnight event.

[wx247]

Still waiting and watching... NWS Springfield very aggressive while Tulsa not nearly so. We shall soon see who is right.

[CrazyC83]

MESOSCALE DISCUSSION 2525
NWS STORM PREDICTION CENTER NORMAN OK
0647 PM CST FRI DEC 26 2008

AREAS AFFECTED...ERN KS INTO WRN MO

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 270047Z - 270145Z

SEVERE STORMS ARE EXPECTED TO DEVELOP BY 03 OR 04Z ACROSS DISCUSSION
AREA...LIKELY REQUIRING THE ISSUANCE OF A WW.

00Z MESOANALYSIS INDICATED PRIMARY SURFACE LOW NE OF RSL AND LATEST
MODEL GUIDANCE REMAINS CONSISTENT IN DEVELOPING THIS FEATURE
GENERALLY EWD TOWARD MKC BY 06Z. AS THIS OCCURS...ATTENDANT COLD
FRONT WILL PUSH SEWD THROUGH THE MID MO VALLEY AND THROUGH WRN INTO
CNTRL KS. 00Z SOUNDINGS FROM BOTH SGF AND LIT INDICATE THAT
CONSIDERABLE MOISTENING HAS OCCURRED WITHIN PRE-FRONTAL BOUNDARY
LAYER SINCE 12Z. HOWEVER...LAYER FROM ROUGHLY 550-750 MB HAS WARMED
WHICH IS EFFECTIVELY RESULTING IN THE MAINTENANCE OF A CAP ACROSS
SYSTEM WARM SECTOR.

PLAN VIEW PROFILER/VWP DATA INDICATE THAT LOW-LEVEL WIND FIELDS ARE
GRADUALLY BACKING OVER THE CNTRL/SRN PLAINS IN THE OZARK PLATEAU
REGION IN RESPONSE TO APPROACH OF LARGE-SCALE TROUGH MOVING THROUGH
THE ROCKIES. THIS PROCESS IS EFFECTIVELY SUPPORTING A MORE NWD FLUX
OF LOW-LEVEL MOISTURE IN ADVANCE OF SURFACE COLD FRONT. THIS
CONTINUED MOISTENING IN CONJUNCTION WITH LEADING EDGE OF HEIGHT
FALLS ASSOCIATED WITH UPPER TROUGH ARE EXPECTED TO SUFFICIENTLY
ERODE CAP SUCH THAT TSTMS ARE LIKELY ALONG OR AHEAD OF COLD FRONT BY
03 OR 04Z.

VERTICAL SHEAR BOTH IN THE LOW LEVELS AND THROUGH A DEEP LAYER WILL
REMAIN QUITE STRONG AND SUPPORTIVE OF SUPERCELL STRUCTURES. WHILE
DAMAGING WINDS AND HAIL WILL BE THE PRIMARY SEVERE WEATHER
THREATS...THE POTENTIAL WILL EXIST FOR A COUPLE OF TORNADOES GIVEN
THE MAGNITUDE OF THE LOW-LEVEL SHEAR AND LOWERING LCL HEIGHTS.

..MEAD.. 12/27/2008


ATTN...WFO...SGF...EAX...TOP...ICT...

LAT...LON 37559723 38919704 39589628 39699468 39229374 38369381
37459391 37019493 37129668 37559723

[CrazyC83]

I'm guessing the northwestern watch could be a Severe Thunderstorm Watch. The real stuff is farther south and east.

[CrazyC83]

SPC AC 270057

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0657 PM CST FRI DEC 26 2008

VALID 270100Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN PLAINS
AND OZARKS...

...SRN PLAINS/OZARK PLATEAU...
A WELL-DEVELOPED UPPER-LEVEL TROUGH OVER THE FOUR CORNER REGION WILL
MOVE EWD ACROSS THE ROCKIES TONIGHT. AHEAD OF THE SYSTEM...A LARGE
50 TO 65 KT LOW-LEVEL JET WILL CONTINUE TO GRADUALLY STRENGTHEN OVER
THE OZARKS. THIS WILL SUSTAIN MOISTURE ADVECTION ACROSS A LARGE WARM
SECTOR. SFC ANALYSIS SHOWS DEWPOINTS IN THE LOWER TO MID 60S F
ACROSS MOST OF THE ERN HALF OF TX...ERN OK AND AR WITH RUC ANALYSIS
SUGGESTING UNSEASONABLY STRONG INSTABILITY EXISTS ACROSS ECNTRL OK.
AS LARGE-SCALE ASCENT INCREASES LATE THIS EVENING DUE TO THE
APPROACHING UPPER-LEVEL TROUGH...SCATTERED THUNDERSTORMS SHOULD
INITIATE ALONG THE INSTABILITY AXIS ACROSS WRN MO...SE KS AND NE OK
AND LATER ALONG THE COLD FRONT FURTHER WEST. THIS CONVECTION SHOULD
QUICKLY EXPAND IN COVERAGE FROM NNE TO SSW WITH SQUALL-LINE
DEVELOPMENT LIKELY BY 12Z ACROSS PARTS OF THE REGION.

CONCERNING THE SEVERE POTENTIAL...RUC ANALYSIS SHOWS 0-6 KM SHEAR
VALUES RANGING FROM AROUND 50 KT IN NORTHEAST TX TO ABOUT 65 KT IN
SE KS. THE VERTICAL SHEAR SHOULD GRADUALLY INCREASE AS A 80 TO 100
KT MID-LEVEL JET APPROACHES THE REGION FROM THE WEST. THIS ALONG
WITH THE AMOUNT OF INSTABILITY ALREADY IN PLACE SHOULD SUPPORT A
SEVERE THREAT SHORTLY AFTER STORMS INITIATE. FORECAST SOUNDINGS ON
THE WRN EDGE OF THE LOW-LEVEL JET SHOW SFC-3 KM SHEAR VALUES OF
ABOUT 400 M2/S2 SUGGESTING THE SHEAR ENVIRONMENT WILL BE FAVORABLE
FOR SUPERCELLS AND A FEW TORNADOES. THE GREATEST SUPERCELL THREAT
WITH POTENTIAL MAY OCCUR NEAR THE ONSET OF THE EVENT IN THE 05Z TO
10Z TIME FRAME WHEN STORMS WILL MORE LIKELY BE DISCRETE. THE
GREATEST TORNADO THREAT SHOULD EXIST WITH SUPERCELLS CLOSER TO THE
LOW-LEVEL JET OVER ERN OK WHERE DEWPOINTS ARE ABOVE 60 F AND 0-1 KM
SHEAR VALUES SHOULD BE AROUND 35 KT LATE TONIGHT. AN ISOLATED STRONG
TORNADO COULD OCCUR IF A SUPERCELL CAN BECOME DOMINANT TO THE EAST
OF A DEVELOPING SQUALL-LINE. AS THIS SQUALL-LINE ORGANIZES FROM
CNTRL MO SSWWD ACROSS ECNTRL OK INTO NE TX VERY LATE IN THE
PERIOD...THE WIND DAMAGE THREAT SHOULD INCREASE. FORECAST SOUNDINGS
ALONG THIS CORRIDOR SHOW 40 TO 50 KT AT ABOUT 1 KM ABOVE THE
SFC...SUGGESTING THE WIND DAMAGE THREAT COULD BECOME MORE WIDESPREAD
IF THE SQUALL-LINE CAN EFFECTIVELY TRANSPORT THE STRONGER WINDS TO
THE SFC.

FURTHER SOUTH ACROSS ECNTRL TX...LARGE-SCALE ASCENT WILL BE WEAKER
AND A CAPPING INVERSION SHOULD EFFECTIVELY HOLD OFF CONVECTIVE
DEVELOPMENT UNTIL VERY LATE IN THE PERIOD. IF STORMS CAN INITIATE BY
12Z...FORECAST SOUNDINGS JUST SOUTH OF THE DALLAS/FORT WORTH AREA
SUGGEST THE SHEAR AND INSTABILITY ENVIRONMENT SHOULD BE SUPPORTIVE
OF ISOLATED WIND DAMAGE AND HAIL. SOUTH FROM THERE...THE CONVECTIVE
POTENTIAL IS MUCH LOWER SUGGESTING A SEVERE THREAT WILL BE HIGHLY
CONDITIONAL.

..BROYLES.. 12/27/2008

CLICK TO GET WUUS01 PTSDY1 PRODUCT

NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z
CURRENT UTC TIME: 0105Z (8:05PM), RELOAD THIS PAGE TO UPDATE THE TIME

[Ed Mahmoud]

Storms just starting to fire near midnight per new NAM, and a very small stable layer right at the surface forecast in Tulsa, so maybe storms won't be quite surface based. But if they are, NAM says "look out".




NAM shows storms haven't quite managed to congeal into a line yet tomorrow at 6 am.



Corsicana, TX sounding- more substantial stable near surface layer, but otherwise quite favorable for tornadoes.


Swall line is reaching my house at lunch time, Ellington Field (ahead of line) sounding for general HOU vicinity not super-favorable for severe, but not super-unfavorable, either. IE, an isolated strong/severe storm is possible. If we could break the soup so common when humid air from the deep Gulf comes in over cooler shelf waters, and get just an hour of sun before the line, that could become a more interesting sounding.

[CrazyC83]

Cells starting to develop south of Muskogee.

[Ed Mahmoud]

Cells starting to develop south of Muskogee.

Struggling a little bit, OUN sounding shows a little bit of a cap still at 800 mb. Good shear and instability, however.

[Ed Mahmoud]

new MCD going up, no text available yet.

MESOSCALE DISCUSSION 2526
NWS STORM PREDICTION CENTER NORMAN OK
0905 PM CST FRI DEC 26 2008

AREAS AFFECTED...ERN OK INTO WRN AR AND SWRN MO

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 270305Z - 270430Z

THE THREAT FOR SEVERE STORMS IS EXPECTED TO INCREASE THROUGH 06Z. A
WW WILL EVENTUALLY BE REQUIRED.

LATEST TRENDS IN REGIONAL RADAR IMAGERY INDICATE SHORT BANDS OF
DEEPENING CONVECTION FROM N OF MLC NWD TO NE OF TUL AND TO THE S AND
SE OF FSM. BASED ON 00Z OBSERVED SOUNDINGS...THIS ACTIVITY IS
LIKELY OCCURRING BENEATH A CAP LOCATED BETWEEN 700 AND 800 MB. WHILE LARGE-SCALE TROUGH AND ASSOCIATED...MORE SIGNIFICANT HEIGHT
FALLS ARE EXPECTED TO REMAIN WELL TO THE W FOR THE NEXT SEVERAL
HOURS...CONTINUED MOISTENING AND WAA ALONG STRENGTHENING 50-60 KT
LLJ ARE EXPECTED TO EVENTUALLY OVERCOME CAP WITH CLUSTERS OF TSTMS
DEVELOPING WITHIN OPEN WARM SECTOR.

RELATIVELY WEAK LAPSE RATES WILL TEND TO LIMIT MLCAPE TO AOB 1000
J/KG DESPITE THE INCREASING MOISTURE. NONETHELESS...THE STRONG
VERTICAL SHEAR /BOTH IN THE LOW LEVELS AND THROUGH A DEEP LAYER/ IN
CONJUNCTION WITH THE INCREASING LARGE-SCALE FORCING WILL BE
SUPPORTIVE OF ORGANIZED STORMS INCLUDING SUPERCELLS CAPABLE OF
DAMAGING WINDS...HAIL AND PERHAPS A COUPLE OF TORNADOES.

..MEAD.. 12/27/2008


ATTN...WFO...LZK...SGF...SHV...TSA...

ETA- as if they read my 9:03 pm CST post.

[ntxweatherwatcher]

What do you think we will get here in DFW?

[Ed Mahmoud]

What do you think we will get here in DFW?

My strictly amateur opinion, based only on the WRF, using the Corsicana 6 am sounding because the stuff has already started in the DFW area, is isolated severe storms, including the possibility of supercells, just before 6 am.


Best bet for local knowledge, the degreed mets on KXAS. 10 pm news, and leave the NOAA radio in auto tonight at bedtime.

OT, but Bedford needs to kill that no drilling ordinance so someone can offer my Mom, and also my Sister and her husband, a gas lease. My sister moved from Euless to Bedford about three years ago, and I saw on the Startlegram web site her old neighborhood had been leased.

[CrazyC83]

How do you tell in the soundings if there is a cap?

[Ed Mahmoud]

If the rate of temperature drop suddenly decreases, or even increases, especially if accompanied by a shift to drier (seen on OUN sounding starting right about 800 mb), that is a cap.

The cap on the OUN sounding isn't particularly strong.


As an amateur, you just look at enough soundings to recognize what a good one looks like. Plus, the world wide internet is a great resource.


http://www.atmos.millersville.edu/~lead/SkewT_HowTo.html

The wind barbs are sort of upside down, since Down Under the warm humid air is coming from the North, but also a good primer
http://www.downunderchase.com/storminfo/stormguide/PDF/Storms07.pdf

[ntxweatherwatcher]

Thanks, I will listen to David Finfrock, or whoever is on tonight. That is the ballpark times they have been giving as well, 6am-9am. I have my weather radio all set up to alert me if any watches or warnings go up. I hate when severe weather comes thru at night!

I agree about the gas leases! We are all for it! Bedford's city council is the problem! They think it will cause houses to explode and such! Nonsense!! Show me the money!!

[Ed Mahmoud]

cells popping near KC...

[Ed Mahmoud]

cells popping near KC...

Watch will be issued (showing up on NWS EAX web page) at 9:55 pm CST

[CrazyC83]

Those cells just developed in a hurry...