Even further out via the GEFS (GFS Ensemble Mean/500mb)...looks like a full latitude trough to me. As always, we will see...Portastorm wrote:Thanks for the info, Andrew. Very good points to consider.
While it is far out (aka 240 hours), the 12z Euro operational run does appear to dump an Arctic "motherlode" into the Plains. I wonder if we're already seeing the teleconnection between the SSW event and the model runs. Something to watch for sure.
What does this mean? Does it mean that if anything was to happen it would be on the icy side instead of the snowy side? Just a wild guess...Andrew wrote:While the 850mb freezing line gets close to SE Texas the 1000-500mb critical thickness line stays in North Texas.
JackCruz wrote:What does this mean? Does it mean that if anything was to happen it would be on the icy side instead of the snowy side? Just a wild guess...Andrew wrote:While the 850mb freezing line gets close to SE Texas the 1000-500mb critical thickness line stays in North Texas.
Andrew wrote:
The 850mb freezing line is the freezing level at 850mb (remember this does not mean freezing at the surface). The critical thickness line from 1000mb to 500mb is where you would expect freezing levels throughout that part of the atmosphere most of the time. While it is loosely used if the critical thickness line ( 5,400 geopotential meter) reaches your area it is a good indication of possible snow in the area. Of course other variables come into play like altitude and moisture levels but it is a good referencing point.
MontgomeryCoWx wrote:Houston prob wouldn't see ice in that run but Conroe and up 105 to Navasota most likely would... I'm good with that!
Warming stratosphere means the energy has to go somewhere, so it goes closer tothe surface. In this case, cold air. Since Siberia and China are having record cold, the cold air could end up here. I could imagine record cold in Siberia and China in 1895, 1899, 1930, 1940, 1949, 1951, 1962, 1976, 1977, 1978, 1979, 1983, 1989, and 2010.Andrew wrote:As others have noted, the GFS is coming around to the other models with less shearing for the second of a series of shortwaves. While the Second piece of energy is farther to the north compared to other models it is less sheared and slower.
Looking at the Sudden Stratospheric Warming (SSW) this event is when you have the polar vortex slow down and change directions which allows for a rise of stratospheric temperature. As a result colder air is allowed to filter south. If you look over in Siberia and China they are currently having record cold and that should begin to shift in our direction. This is something that will be discussed more once we get closer to it effecting us.
The Euro is remaining wet with the 12z run. This run is a little bit faster but still shows a very moist 850mb and 700mb profile with RH getting close to 100%. While the 850mb freezing line gets close to SE Texas the 1000-500mb critical thickness line stays in North Texas. Something to watch as we get closer. More to watch as we get closer.
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000
FXUS64 KHGX 292108
AFDHGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
308 PM CST SAT DEC 29 2012
.DISCUSSION...
IT APPEARS THAT A CONSTANT STREAM OF PACIFIC MOISTURE WILL KEEP
CIRRUS CLOUDS OVER THE REGION THROUGH SUNDAY. THE ADDITIONAL CLOUD
COVER WILL LIKELY KEEP MIN TEMPS A BIT WARMER THAN GUIDANCE
SUGGESTS. HIGH PRESSURE WILL MOVE EAST OF THE REGION ON SUNDAY AND
ONSHORE WINDS WILL RESUME AND AN INCREASE IN LOW LEVEL MOISTURE IS
EXPECTED TO BEGIN LATE SUNDAY AFTN. A WARM FRONT WILL APPROACH THE
UPPER TEXAS COAST ON SUNDAY NIGHT WITH WARMER TEMPS EXPECTED. THE
LOW LEVEL JET INCREASES WITH FCST SOUNDINGS SHOWING A SATURATED
LAYER BENEATH A CAPPING INVERSION. THIS LOOKS VERY SIMILAR TO THE
WARM AIR ADVECTION PATTERN FROM A FEW DAYS AGO SO WILL CARRY LIGHT
RAIN...DRIZZLE AND FOG FOR SUN NITE INTO MONDAY. MOISTURE LEVELS
DEEPEN FURTHER ON MONDAY AND FCST SOUNDINGS SHOW A FAIRLY LARGE
SATURATED LAYER AND INCREASING INSTABILITY. LIFT WILL INCREASE
FURTHER MONDAY NIGHT AS AN UPPER TROUGH MOVES ACROSS THE SOUTHERN
PLAINS. A SFC COLD FRONT AND ADDITIONAL LIFT FROM FAVORABLE JET
DYNAMICS WILL ENHANCE RAIN CHANCES FOR MONDAY NIGHT INTO EARLY
TUESDAY. STILL SOME TIMING DIFFERENCES BETWEEN THE GFS AND ECMWF
AND HAVE GONE WITH THE ENSEMBLE MEANS WHICH FAVOR THE HIGHEST RAIN
CHANCES MON NITE/EARLY TUES BETWEEN 00-12Z.
LONG RANGE MODELS ARE IN MUCH BETTER AGREEMENT WITH REGARD TO
TEMPS/RAIN CHANCES FOR TUE-THU. SOUTHWEST WINDS ALOFT WILL OVER
RIDE NORTHERLY SURFACE WINDS. ISENTROPIC UPGLIDE WILL INCREASE
AND PERIODS OF RAIN ARE LIKELY TUESDAY THROUGH EARLY THURSDAY.
AGAIN...THERE ARE SOME TIMING DIFFERENCES BUT THERE IS A GROWING
CONSENSUS THAT WED/WED NITE WILL BE VERY WET. THE CLOUD COVER AND
PRECIP WILL PREVENT MAX TEMPS FROM WARMING OUT OF THE 40S BOTH
WED/THU. UNDERCUT GUIDANCE WITH REGARD TO MAX TEMPS AND WENT A
TOUCH WARMER AT NIGHT. EXTENDED POP GUIDANCE IS ALREADY NEAR 90
PERCENT AND SEE NO REAL ARGUMENT AGAINST SUCH HIGH POP NUMBERS.
UPPER FLOW REMAINS OUT OF THE SOUTHWEST THROUGH THURSDAY NIGHT.
MODELS INSIST THAT RAIN WILL END EARLY THURSDAY BUT THE FLOW ALOFT
SUGGESTS AN UNSETTLED WEATHER PATTERN WILL CONTINUE INTO EARLY
FRIDAY. 43
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000
FXUS64 KFWD 292127
AFDFWD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
327 PM CST SAT DEC 29 2012
.DISCUSSION...
WATER VAPOR SHOWS A LARGE UPPER LEVEL LOW OVER CALIFORNIA DIGGING
SOUTH TOWARD BAJA. THE UPPER LOW IS BEGINNING TO TAP INTO SOME
SUBTROPICAL PACIFIC MOISTURE...WHICH WILL BE ARRIVING INTO NORTH
TEXAS TONIGHT AND SUNDAY IN THE FORM OF INCREASING MID-HIGH
CLOUDINESS. THESE CLOUDS WILL IMPEDE OPTIMAL RADIATIONAL COOLING
LATER TONIGHT DESPITE SURFACE WINDS BECOMING LIGHT. HOWEVER LOWS
WILL STILL BOTTOM OUT IN THE 20S JUST ABOUT AREA WIDE. THE MID-
HIGH CLOUDS WILL BECOME DENSE BY SUNDAY AFTERNOON WHICH WILL
LIMIT THE WARM UP DESPITE INCREASING SOUTH WINDS.
THE UPPER LEVEL LOW WILL BECOME GENERALLY STATIONARY OVER THE
DESERT SOUTHWEST SUNDAY...BUT A SHORTWAVE WILL ROTATE AROUND IT
AND COME ACROSS NORTH TEXAS ON MONDAY. IN ADVANCE OF THE IMPULSE
ISENTROPIC LIFT WILL INTENSIFY SUNDAY EVENING WITH RAIN BREAKING
OUT ACROSS THE NORTHWEST HALF OF THE AREA. INITIALLY THIS RAIN
WILL FALL AS VIRGA SUNDAY AFTERNOON...BUT THE LOW LEVELS WILL BE A
BIT TOO DRY FOR ANYTHING MORE THAN SPRINKLES UNTIL AFTER SUNSET.
RAIN WILL CONTINUE TO INCREASE IN COVERAGE AND INTENSITY GOING
INTO MONDAY MORNING WITH A LARGE SHIELD OVERSPREADING THE REGION
FROM WEST TO EAST DURING THE DAY. RAINFALL AMOUNTS SHOULD RANGE
FROM 0.75 INCH IN THE NORTH TO 0.25 INCH IN THE SOUTH BEFORE THE
ACTIVITY COMES TO AN END LATE MONDAY AFTERNOON IN THE WEST AND
EARLY MONDAY EVENING IN THE EAST. DUE TO THE STRONG WARM ADVECTION
ATOP THE VERY MOIST/COOL SURFACE AIRMASS...IT LOOKS LIKE FOG WILL
BECOME WIDESPREAD AND AFFECT THE REGION DURING THE DAY MONDAY. AS
THE SHORTWAVE PASSES THE AREA...IT WILL ALLOW A COLD FRONT TO MOVE
THROUGH MONDAY NIGHT. DRY/COLD ADVECTION SHOULD DISPERSE THE FOG
AND TEMPERATURES WILL COOL INTO TUESDAY MORNING AS THE COLD
AIRMASS RESIDING OVER THE PLAINS SLOSHES BACK TO THE SOUTH.
12Z GUIDANCE HAS CHANGED REGARDING ITS HANDLING OF A PIECE OF
ENERGY THAT ROTATES THROUGH WESTERN CANADA AND INTO THE STATES BY
MIDWEEK. TODAY THE GUIDANCE HAS EITHER SLOWED THE TIMING OF THAT
ENERGY DOWN OR HAS FORECAST IT TO DROP INTO THE STATES MUCH
FARTHER WEST THAN YESTERDAY. THE CHANGE RESULTS IN LESS NORTHERLY
WINDS AT 850MB WHICH WOULD HAVE SERVED TO DRY THE REGION OUT AND
LIMIT PRECIP POTENTIAL WED-THURS AS ANOTHER SHORTWAVE ROTATES IN
FROM THE SOUTHWEST AROUND THE AFOREMENTIONED UPPER LOW. PRECIP HAD
BEEN FORECAST BY THE CANADIAN AND ECMWF...AND NOW THAT THE GFS IS
ON BOARD...WILL GO AHEAD AND BRING POPS INTO THE FORECAST
WEDNESDAY IN THE SOUTH AND FOR MOST OF THE AREA WEDNESDAY NIGHT.
ALTHOUGH WE HAVE SEEN SOME SUBTLE FEATURES CHANGE IN THE LATEST
MODEL GUIDANCE...THERE IS HIGH CONFIDENCE ON THE FORECAST UPPER
LEVEL SYNOPTIC PATTERN. THIS PATTERN WILL FEATURE A RIDGE OVER THE
PACIFIC NORTHWEST...WITH TELECONNECTIONS FAVORING A BROAD POSITIVE
TILT TROUGH AXIS FROM HUDSON BAY TO THE FOUR CORNERS. THIS IS A
SYNOPTIC PATTERN THAT ALWAYS SEEMS TO END UP BEING COLDER THAN
FORECAST BY THE MODELS. I AM AT A LOSS FOR THE TECHNICAL REASON
BEHIND THE MODEL BIAS...BUT THE UPPER PATTERN DOES ALLOW FOR A
PROLONGED FETCH OF NORTHERLY WINDS AT THE SURFACE TO TRANSPORT
COLD AIR SOUTHWARD OVER THE COURSE OF 2+ DAYS. SEEING THIS PATTERN
RAISES CONCERNS FOR SURFACE TEMPS COLDER THAN CURRENTLY FORECAST
AND SUBSEQUENTLY WINTER WEATHER WHEN THAT SHORTWAVE MOVES ACROSS
FROM THE SOUTHWEST WEDNESDAY NIGHT. THE ECMWF AND CANADIAN SHOW A
POTENTIAL FOR SNOW ACROSS CENTRAL TEXAS AND THAT FORECAST SEEMS
REASONABLE. ELSEWHERE ACROSS NORTH TEXAS...THE COLD AIR MAY NOT BE
DEEP ENOUGH FOR SNOW...AND SOME TYPE OF WINTER MIX WOULD BE THE
RESULT. IT IS TOO EARLY FOR PRECIP TYPE FORECASTING BUT CONFIDENCE
IS HIGH ENOUGH TO INSERT A LOW CHANCE OF RAIN/SNOW MIX ACROSS THE
WESTERN/SOUTHWESTERN ZONES WEDNESDAY NIGHT. HAVE KEPT PRECIP
LIQUID OVER THE REMAINING AREAS...BUT AS CONFIDENCE THAT THE
MODELS HAVE SETTLED DOWN ON ONE SOLUTION INCREASES THIS MAY BE
EXPANDED. EITHER WAY...EXPECT GENERALLY CLOUDY AND CHILLY WEATHER
MID-LATE WEEK. HAVE GONE QUITE A BIT COOLER THAN GUIDANCE FOR HIGH
TEMPS THROUGH FRIDAY. THE UPPER TROUGH AXIS WILL FINALLY MOVE EAST
BY SATURDAY WITH CLEARING SKIES AND WARMING TEMPERATURES.
TR.92
&&Code: Select all
000
FXUS64 KEWX 292120
AFDEWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
320 PM CST SAT DEC 29 2012
.DISCUSSION...
RATHER COOL-CLOUDY...SOMETIMES WET CONDITIONS PREVAILING FOR MUCH
OF THIS FORECAST PACKAGE. THE MEAN TROUGH AXIS REMAINS WEST OF
TEXAS AND A SERIES OF SHORT WAVES TRAVERSE THE AREA IN THE SWLY
FLOW ALOFT. IN ADDITION...AFTER A BRIEF WARM-UP ON MONDAY...A
COLD FRONT PUSHES THRU EARLY TUESDAY WITH A COOL AIRMASS REMAINING
OVER S TX THRU THE REMAINDER OF THE WEEK AND INTO NEXT WEEKEND.
THE ECMWF/GFS IN A LITTLE BETTER CONSENSUS IN THE LONG TERM BY
EJECTING THE UPPER TROUGH/LOW EAST OF THE AREA BY SATURDAY WITH
DRIER CONDITIONS PREVAILING.
CONSIDERABLE MID LEVEL CIRRUS TRAVERSING THE AREA THIS AFTERNOON
AND WILL CONTINUE TO INCREASE/LOWER LATE TONIGHT INTO SUNDAY. LOWS
TONIGHT WILL BE TRICKY AS DEW POINTS REMAIN VERY LOW AND WINDS
WILL BE LIGHTER THAN LAST NIGHT. HOWEVER THICKER CIRRUS COULD RESULT
IN WARMER MINS THAN CURRENTLY FORECAST. OTHERWISE MOSTLY CLOUDY
SUNDAY WITH A INCREASING RAIN CHANCES FROM THE WEST...STARTING
WITH A FEW SPRINKLES OVER THE RIO GRANDE PLAINS AND WESTERN EDWARDS
PLATEAU SUNDAY MORNING...BECOMING MORE WIDESPREAD LIGHT RAIN AND
SHOWERS BY SUNDAY NIGHT INTO MONDAY AND MONDAY NIGHT. COULD SEE
ISOLATED THUNDERSTORMS LATE MONDAY/MONDAY NIGHT OVER THE EASTERN
CWA AS THE LOW LEVEL JET DEVELOPS AHEAD OF AN UPPER LEVEL
DISTURBANCE AND COLD FRONT. RAIN CHANCES SHOULD PUSH MOSTLY SOUTH
OF THE CWA TO NEAR THE COAST ON NEW YEARS DAY...HOWEVER ANOTHER
UPPER AIR DISTURBANCE QUICKLY APPROACHES FROM THE WEST BY
WEDNESDAY. THEREFORE RAIN CHANCES WILL BRIEFLY RETURN TO THE
EASTERN HALF THE CWA AT MID WEEK...TAPERING OFF FROM THE WEST
THURSDAY. WEDNESDAY COULD BE EVEN COOLER THAN CURRENTLY FORECAST
DUE OVERRUNNING MOISTURE/CLOUDS OVER THE COLD AIRMASS NEAR THE
SURFACE.
DRIER CONDITIONS PREVAILING FRIDAY INTO SATURDAY AS A ZONAL FLOW
EVOLVES FOR THE WEEKEND WITH DECREASING CLOUDS AND MORE DIURNAL
VARIATION IN TEMPERATURES.
&&
I knew it wouldn't happen 
no sleet.....ugh.
I think the 00z runs will be telling for tomorrow's AFDs. If they continue the trend towards the Euro and CMC then AFDs will reflect that more.Portastorm wrote:Great AFDs out of Fort Worth and Houston. I'm at a loss to understand EWX's last several AFDs. They seem oblivious to the Euro op runs, the CMC, and the GFS' growing trend towards the Euro solution.
Wow. Interesting. This early in the winter season. Ok, we have Jack Cruz saying, "No winter weather for Houston this winter season" LOL.JackCruz wrote:Quote me on this, Houston will get nothing this winter.
