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Texas/New Mexico/Louisiana/Mexico Obs And Discussion Thread Part 5


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MESOSCALE DISCUSSION 0159
NWS STORM PREDICTION CENTER NORMAN OK
0727 AM CST SUN MAR 02 2014

AREAS AFFECTED...PORTIONS OF CNTRL/SRN/ERN OK...N-CNTRL TX...NRN
AR...SRN MO

CONCERNING...WINTER MIXED PRECIPITATION

VALID 021327Z - 021930Z

SUMMARY...AN INCREASE IN THE COVERAGE AND INTENSITY OF WINTER MIXED
PRECIPITATION IS ANTICIPATED ACROSS PARTS OF THE SRN PLAINS TO THE
OZARK PLATEAU THIS MORNING...WITH SIMILAR ACTIVITY PERSISTING INTO
THE AFTERNOON.

DISCUSSION...REGIONAL 12Z RAOBS SAMPLE A PLUME OF ELEVATED BUOYANCY
ROOTED ATOP THE STRONG INVERSION OVERLYING AN ARCTIC AIR MASS THAT
IS SPREADING SWD ACROSS THE REGION. INFRARED AND WATER VAPOR
SATELLITE IMAGERY SUGGEST THAT THE FRINGES OF STRONGER
ASCENT/MID-HIGH CLOUDS PRECEDING A SRN-STREAM IMPULSE OVER AZ/NM ARE
ENCROACHING ON THIS BUOYANCY. MOSAIC RADAR IMAGERY ALREADY INDICATES
THE DEVELOPMENT OF ISOLATED CONVECTION PRODUCING SLEET FROM SWRN OK
TO THE OZARKS. AS THE IMPULSE CONTINUES TO APPROACH THE AREA...THE
INCREASE IN ASCENT WILL ENCOURAGE THE GROWTH OF ADDITIONAL ELEVATED
CONVECTION THROUGH THE MORNING...WHILE PRECIPITATION FALLOUT FROM
MID/HIGH-LEVEL CLOUDS STIMULATES PRECIPITATION FROM THE LOWER
STRATUS DECK /SEEDER-FEEDER MECHANISM/.

DESPITE ELEVATED WARM NOSE TEMPERATURES OF 6-12C AROUND H85
SUPPORTING COMPLETE MELTING OF HYDROMETEORS PER THE 12Z
SOUNDINGS...VERY COLD TEMPERATURES IN THE SHALLOW PBL -- I.E. AOB
-10C WILL LIKELY SUPPORT SLEET WITH THE CONVECTION. HOWEVER...FOR
AREAS FROM NRN AR TO SERN/S-CNTRL OK AND ADJACENT N-CNTRL TX WHERE
MAXIMUM TEMPERATURES BENEATH THE FRONTAL INVERSION WILL BE A LITTLE
WARMER -- THOUGH STILL BELOW 0C -- FREEZING RAIN WILL BE LIKELY.
LIQUID-EQUIVALENT PRECIPITATION RATES OF 0.05-0.15 INCH PER HOUR
WILL BE LIKELY. THIS COULD TRANSLATE TO SLEET ACCUMULATION RATES
AROUND 0.25 INCH PER HOUR...PERHAPS LOCALLY HIGHER. THE HIGHEST
PRECIPITATION RATES ARE EXPECTED TO OCCUR FROM THE OZARK PLATEAU TO
SERN/S-CNTRL OK AND ADJACENT N-CNTRL TX INVOF A PLUME OF 0.75-1-INCH
PW PER GPS DATA.

THE OVERALL INCREASE IN COVERAGE AND INTENSITY OF SLEET/FREEZING
RAIN SHOULD CONTINUE THROUGH LATE MORNING AND INTO THE
AFTERNOON...WITH THE POTENTIAL FOR THUNDERSTORM ACTIVITY TO LOCALLY
ENHANCE PRECIPITATION RATES.

..COHEN.. 03/02/2014

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Already down to 29, IMBY, and have been below freezing for a good while now.  Temps look to be already running below the 12z NAM with the NAM giving most of DFW 0.20” plus with higher amounts as your run NE.  The 9z SREF looks to be 0.30” area wide with the same trend of increasing amounts as you head NE.  Will be interesting to see if enough liquid is squeezed out to make this an event or not.

 

ETA: The RAP is juiced up! :lol::weenie: :weenie:

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Morning Update from Jeff:

 

Powerful arctic cold front will sweep across the region today with a significant drop in temperatures.

 

Arctic boundary is moving quickly southward this morning with a 30-40 degree temperature drop across the boundary (Austin is 72 while Waco is 35). Boundary will race southward and reach our NW counties before noon and push to near US 59 by 300-400pm and off the coast by early evening. Upstream temperatures at Amarillo are 8 and in the teens across much of OK so this air mass is very cold for early March.

 

Severe Threat:

Mornings soundings from LCH and CRP showed a fairly impressive capping inversion in place across the region with saturation of the air mass below the cap. With better moisture in place today…it will be hard to mix out the low stratus clouds over the region and suspect there will only be a few breaks in the overcast across the region which will keep instability on the lower side in the 800-1000J/kg instead of closer to 1500J/kg. Forecast models erode the cap this afternoon and allow convection to develop along the leading edge of the frontal lift. Think the arctic boundary will move too fast southward and outrun the developing storms cutting the updrafts off from the surface and making them quickly elevated which lessens the severe threat over the region. Could still see a few severe hail and wind reports especially NE of a line from College Station to Conroe to Liberty where capping will be weakest and storms have the best chance of being rooted near the surface.

 

Winter Precipitation:

Incoming air mass is very cold and forecast models have been too warm with upstream temperatures which raises the concern this evening that light rain following the frontal passage could change to freezing rain along a north of a HWY 105 line. Warm temperatures since Friday has greatly warmed both ground and roadway surface temperatures and even if temperatures fall into the 30-32 range do not think ice accumulation will be significant. With that said overnight lows will fall into the upper 20’s north of HWY 105 which may result in freezing over residual water on bridges and overpasses after the precipitation ends around midnight. Given very warm roadway surface conditions, think surface temperatures will need to fall into the 27-29 range for ice to form and this will be possible in the region from College Station to Lake Livingston after midnight.

 

Other aspect will be the potential for a freeze warning for areas N of I-10 tonight. While the area has had several hard freezes this winter the recent warm spells have allowed vegetation to bud and freezing temperatures will damage the new sensitive growth which would fall within the range of a late season freeze warning. Wind chills tonight will run 15-25 degrees across the area.

 

Early Week:

Cold arctic dome will entrench over the area for much of the week with active flow remaining in place from the WSW. This flow will bring several disturbances across the area and generate periods of rainfall. First disturbance will cross the area late Monday into Tuesday. Surface temperature profiles suggest mainly a rain event, but surface temperatures could be very near freezing Tuesday morning north of HWY 105 for a brief period of freezing rain or sleet. Highs on Monday will only reach the mid 40’s under north winds and cloudy skies (about 35 degrees colder than today). Next system approaches late Tuesday into Wednesday with another chance of rainfall across the area. Temperatures will remain cold for early March for most of the week with lows 30-35 Monday and Tuesday and highs only in the 40’s both Monday and Tuesday. Wednesday will again be cold with clouds and rain with lows in the upper 30’s and highs in the lower 50’s.

 

Should start to see a warming trend toward the end of the week ahead of yet another weather system next Saturday.

 

Day 1 Severe Weather Outlook:

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The SPC 09Z SREF continues to be very suggestive of a freezing rain/sleet potential across our Region  including Metro Houston early tomorrow morning and again mainly across Central Texas early Tuesday morning.
 

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Ugh...

 

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1122 AM CST SUN MAR 2 2014

...WIND CHILL ADVISORY IN EFFECT FROM 1 AM THROUGH 8 AM...

.STRONG NORTH WINDS AND MUCH COLDER AIR WILL WILL SWEEP THROUGH
THE ADVISORY AREA THIS AFTERNOON. AFTER MIDNIGHT TEMPERATURES
WILL FALL TO 25 TO 30 DEGREES WITH MODERATE TO STRONG NORTH WINDS.
WIND CHILL READINGS WILL RANGE FROM 22 DOWN TO 14 DEGREES
ESPECIALLY BETWEEN 4 AM AND 8 AM.

TXZ163-164-176-177-195>198-030800-
/O.NEW.KHGX.WC.Y.0001.140303T0700Z-140303T1400Z/
BRAZOS-BURLESON-GRIMES-HOUSTON-MADISON-TRINITY-WALKER-WASHINGTON-
INCLUDING THE CITIES OF...BRENHAM...BRYAN...CALDWELL...
COLLEGE STATION...CROCKETT...GROVETON...HUNTSVILLE...
LAKE SOMERVILLE...MADISONVILLE...NAVASOTA...TRINITY
1122 AM CST SUN MAR 2 2014

...WIND CHILL ADVISORY IN EFFECT FROM 1 AM TO 8 AM CST MONDAY...

THE NATIONAL WEATHER SERVICE IN HOUSTON/GALVESTON HAS ISSUED A
WIND CHILL ADVISORY...WHICH IS IN EFFECT FROM 1 AM TO 8 AM CST
MONDAY.

* TIMING...STRONG NORTH WINDS AND MUCH COLDER AIR WILL WILL SWEEP
  THROUGH THE ADVISORY AREA THIS AFTERNOON AND TEMPERATURES WILL
  DROP INTO THE 40S AND UPPER 30S. AFTER MIDNIGHT TEMPERATURES
  WILL FALL TO 25 TO 30 DEGREES WITH MODERATE TO STRONG NORTH
  WINDS. WIND CHILL READINGS WILL RANGE FROM 22 DOWN TO 14
  DEGREES ESPECIALLY BETWEEN 4 AM AND 8 AM.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WIND CHILL ADVISORY MEANS THAT VERY COLD AIR AND STRONG WINDS
WILL COMBINE TO GENERATE LOW WIND CHILLS. THIS WILL RESULT IN
FROST BITE AND LEAD TO HYPOTHERMIA IF PRECAUTIONS ARE NOT TAKEN.
IF YOU MUST VENTURE OUTDOORS...MAKE SURE YOU WEAR A HAT AND
GLOVES.

 

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Winter Storm Warning issued for the Metroplex.

 

Advisories extended further S to include Bosque, Comanche, Eastland, Erath, Hamilton, Hill, Hood, Mills, Palo Pinto, Parker, Somervell, Stephens Counties until 9:00 PM

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I spend 4 days reading the NYC subforum, and didn't even become aware until yesterday the North Texas ice threat.  They went from a 12 to 18 inch GFS/Euro snowstorm to a 1-4 inch snowstorm on the models in 3 days.  Mass weenie suicide time.

 

 

 

 

 

If it ends in the evening as forecast, I'd think TXDOT would get the major commuter route overpasses treated before the morning rush.

 

26ºF (-3º Canadian) with light freezing rain last ob I saw at DFW.  New ob should be available shortly.

 

NE corner of Texas under WSW and a severe t-storm warning, well, that rocks.

post-138-0-53294000-1393786552_thumb.gif

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Nothing in Arlington right now and I live 12 to 15 minutes southwest of the airport as the crow flies. Also looks like dryslotting on radar starting to happen to the southwest of the Metroplex? What about broad precip shield out in West Texas?

 

NWS SJT DYX radar, the thunder-snow and sleet is trying to fill in to the SW of the Metroplex...

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sleet/snow mix reported in Marlin between Waco and CLL

 

...and I was concerned about severe T-storms between CLL and Houston.  Man, the cold has overperformed again, although significant wintry precip escaped from our clutches 4 times this year.  What Karma it would be to get hit this time.  lol

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I'll admit, when I went to sleep last night, I didn't think I would be in a Mesoscale Discussion today, and if I was, it wouldn't be this type!

 

mcd0162.gif

 

MESOSCALE DISCUSSION 0162
NWS STORM PREDICTION CENTER NORMAN OK
0336 PM CST SUN MAR 02 2014

AREAS AFFECTED...PORTIONS OF E AND NE TX INTO SWRN AR

CONCERNING...WINTER MIXED PRECIPITATION

VALID 022136Z - 030130Z

SUMMARY...SHOWERS AND TSTMS WILL CONTINUE TO DEVELOP OVER PORTIONS
OF EAST INTO NORTHEAST TX AND SWRN AR THIS AFTERNOON INTO THE
EVENING WITH ACTIVITY MOVING NEWD ACROSS THESE SAME AREAS.
MEANWHILE...A COLD AIR MASS IS EXPECTED TO MAINTAIN A GREATER SWD
MOVEMENT ACROSS E TX AS COMPARED TO NRN LA AS A COLD FRONT ADVANCES
SSEWD REACHING SE TX AND THE TX COAST TOWARD 00Z. LOCATIONS IN THE
WAKE OF THE COLD FRONT CAN EXPECT A CHANGE IN PRECIP-TYPE FROM RAIN
TO A MIX OF SNOW...FREEZING RAIN AND CONVECTIVELY-ENHANCED SLEET
SHOWERS. FREEZING RAIN RATES OF 0.05-0.1 INCH PER HOUR AND LOCALLY
TO 0.15 INCH PER HOUR...ESPECIALLY WITH TSTMS...ARE POSSIBLE. THESE
RATES ARE VERIFIED PER RECENT SURFACE OBSERVATIONS IN THE WRN EDGE
OF THE DISCUSSION AREA.

DISCUSSION...TRENDS IN REGIONAL RADAR IMAGERY...LIGHTNING DATA...AND
CIMSS GOES-R CLOUD TOP COOLING AND OVERSHOOTING TOP PRODUCTS
INDICATED CONVECTION AND EMBEDDED TSTMS CONTINUING TO INCREASE IN
COVERAGE AND INTENSITY SINCE 1930Z ACROSS NORTHEAST TX TO SWRN AR.
WHILE THE OVERALL HAIL THREAT HAS REMAINED LOW PER WDSS-II MESH
PRODUCT /E.G. MESH HAIL SIZE UP TO 0.5-0.8 INCH/...THE GREATER
CONCERN WITH THIS ACTIVITY WILL BE AN EXPECTED CHANGE IN PRECIP-TYPE
FROM W-E. MUCH OF THE WRN HALF OF THE DISCUSSION AREA SHOULD
EXPERIENCE THIS CHANGE TO WINTRY PRECIPITATION BY 00Z...WITH THE
SURFACE 32 F ISOTHERM EXPECTED TO EXTEND FROM INVOF TXK TO NEAR CLL
BY THAT TIME.

THE CURRENT INCREASE IN TSTM COVERAGE...WHICH IS FORECAST TO PERSIST
INTO THE EVENING...IS OCCURRING AS STRONGER FORCING FOR ASCENT
ATTENDANT TO THE UPSTREAM SHORTWAVE TROUGH CONTINUES TO SPREAD EAST
TOWARD THE ARKLATEX REGION. THIS ASCENT ATOP AN INFLUX OF
WARM/MOIST AIR ALONG A 40-45 KT SLY LLJ BEING LIFTED ISENTROPICALLY
ATOP THE COLDER POST-FRONTAL SURFACE AIR MASS WILL MAINTAIN THE
THREAT FOR TSTMS. THE EQUATOR-WARD INCREASE IN THE DEPTH OF THE
COLD AIR IN THE WAKE OF THE COLD FRONT WILL RESULT IN VERTICAL
THERMAL PROFILES TRANSITIONING TO ONES SUPPORTIVE OF MIXED WINTRY
PRECIPITATION...WITH TSTMS ENHANCING THE PRECIP RATES.

..PETERS.. 03/02/2014


ATTN...WFO...LZK...SHV...HGX...FWD...

LAT...LON 31729693 32579629 33549521 34609385 34559334 34289318
33909362 33249398 31959472 30809557 30729638 31229702
31729693 

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Wow is all I can say about this storm right now I'm Tyler. Intense lightning, thunder, and heavy sleet. Everything covered in white. Amazing to watch cars drive by and turn up water from earlier and it's freezing almost instantly! Just pouring sleet currently! Best storm of the winter!

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