February-Comfortable Days/Cool Nights To The Month

[jasons2k]

I had .73" earlier today and yes that is a nice surprise round II with the front on the way.

[srainhoutx]

NCEP Status Update for the 00Z suite stated 6 of the G-IV drops made it into the NAM while 18 are available for the GFS and the rest of the Global guidance.

[Katdaddy]

Severe weather threat increasing for SE TX Thursday. From this morning's Houston-Galveston AFD:

LATESTMODEL RUNS HAVE TRENDED SLIGHTLY SLOWER WITH THE APPROACH OF THE
UPPER TROUGH WHICH WILL ALLOW THE WARM FRONT TO LIFT NORTHWARD
ACROSS MUCH OF THE EASTERN HALF OF THE STATE BY EARLY THURSDAY.
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP LATE WEDNESDAY
NIGHT ACROSS WEST TEXAS AND SPREAD EASTWARD OVERNIGHT...WITH THE
THREAT FOR SEVERE WEATHER INCREASING AS THEY MOVE INTO THE WARM
SECTOR ACROSS CENTRAL AND SOUTHEAST TEXAS. A STRONG LOW LEVEL JET
COUPLED WITH A 500MB JET STREAK MOVING INTO CENTRAL TEXAS WILL
CREATE STRONGLY CURVED HODOGRAPHS ACROSS OUR REGION WITH THE
POTENTIAL FOR ORGANIZED CONVECTION WITH ROTATING UPDRAFTS. WHILE
THERE IS STILL SOME CONCERN ABOUT LIMITED INSTABILITY OVERALL
CONFIDENCE IN SEVERE THREAT FOR THURSDAY MORNING IS INCREASING.
MORE INFORMATION ON THE EXPECTED SEVERE WEATHER THREATS CAN BE
FOUND IN THE HAZARDOUS WEATHER OUTLOOK.

[srainhoutx]

Morning e-mail from Jeff:

Next storm system quickly arrives into the area Wed-Thurs with strong to severe thunderstorms possible.

Fast progressive upper air pattern will bring another upper level storm system and Pacific cold front into the area by Thursday. Cool front from last night has pushed into the NW Gulf this morning with a dry and cool air mass in place over SE TX. High clouds are already starting to stream ENE from central MX in response to the next digging trough out west. Front will stall over the NW Gulf today while moisture begins to return northward from both the Gulf and Pacific above the surface cold dome. Will see a rapid increase in cloud cover from SW to NE tonight as moisture surges northward above the cold dome. Skies will be cloudy be sunrise Wednesday with lifting of the incoming moist air mass over the cool dome producing periods of showers, light rain, fog and drizzle. Showers will become numerous by early afternoon as a lead short wave crosses the area helping to enhance lift. Additionally, the warm front will move northward and approach the coast by mid afternoon on Wednesday. Surface based instability appears limited, but there appears to be some elevated instability and thunderstorms may become more numerous as the day progresses near and north of the warm front. Not expecting much severe weather on Wednesday, but a few of the elevated storms could produce some hail.

As a surface low deepens over central TX on Wednesday night, the attached warm front downstream over the upper TX coast should progress inland and through much of SE TX by Thursday morning. Area will become under the influence of the warm sector, but also under the increasing influence of capping from the SSW. Approach of the main upper trough across NW TX into OK will push a cold front eastward across central TX and as this boundary encounters the warm and moist air mass east of I-35 expected thunderstorms to develop. Strong linear forcing is suggested indicating more of a line than discrete cells. However strong lift will also be overspread the northward moving warm front which should be along a line from near Temple to Lufkin Thursday morning. Convection will become increasingly surface based and the air mass will be highly sheared in the low level, so supercells with tornadoes will be possible along and near the warm frontal boundary which could be over our northern set of counties. One drawback for a significant severe weather outbreak appears to be limited instability with CAPE values of 800-1500 J/kg over the region. Low level shear is impressive however and storms that are able to root near the surface will have rotating updrafts.

South of the warm front across the warm sector and the rest of SE TX, the linear forcing along the advancing front combined with a strong upper level sub-tropical jet overhead should result in a line of thunderstorms or squall line to move across the area from W to E during the morning hours. There will be a severe threat with this line also…with the main threat being wind damage, but isolated tornadoes in any “notches” in the line will be possible given low level helicity values of 200-400 m^2/s^2. How far south this line of storms extends will depend on the intensity of the capping advecting NNE from S TX. Forecast models are not overly excessive with the cap, but time of day (early to mid morning) does not bode well for any heating as compared to yesterday when surface heating was able to weaken the cap and lift from a short wave enticed convection through the mid level warm layer. Will review the severe parameters again Wednesday AM as by this point there should be a decent handle on the threat and the most likely severe modes.

Cold front Thursday afternoon slows and stalls just offshore with clouds and possible showers lingering near the coast early Friday. GFS has come in wet on Saturday as this model amplifies another short wave and drops it across TX, but no other models currently suggest this scenario. For now will follow the dry guidance and keep skies partly cloudy and conditions dry unless the other major models begin to trend toward the wetter GFS solution.

Severe Weather Outlook for Wednesday

The attachment 02192013 SPC day2otlk_0700.gif is no longer available

Severe Weather Outlook for Thursday:[/i]

[srainhoutx]

While the focus has been for the severe weather potential for the Wednesday/Thursday Storm, it is noteworthy that the cold sector will drop some impressive snow totals with blizzard conditions across large area creating all sort of travel issues across the Country. The areas that have been in an exceptional drought will benefit from that heavy snow.

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
448 AM EST TUE FEB 19 2013

VALID 12Z TUE FEB 19 2013 - 12Z FRI FEB 22 2013

...UPPER GREAT LAKES THROUGH NEW ENGLAND...

MODELS REMAIN STRONGLY CLUSTERED WITH THE CYCLONE NEAR LAKE
MICHIGAN TRACKING ACROSS SOUTHERN ONTARIO/QUEBEC BEFORE REFORMING
IN THE GULF OF MAINE EARLY WEDNESDAY THEN MOVING INTO THE
ATLANTIC. THE LOW'S NORTHERN TRAJECTORY SUGGESTS THAT THE UPPER
PENINSULA OF MICHIGAN SHOULD RECEIVE THE HIGHEST PROBABILITIES OF
HEAVY SNOW THROUGH TODAY BEFORE NORTHERN MAINE JOINS AS WELL
TUESDAY NIGHT/WEDNESDAY AS THE ELONGATED PLUME OF MOISTURE
ORIGINATING FROM THE GULF OF MEXICO BEGINS TO ASCEND THE HIGHER
ELEVATIONS IN THE NORTH...THUS SUPPORTING LOW PROBABILITIES OF A
FOOT OR MORE OVER NORTHERN MAINE BEFORE THE CYCLONE LIFTS
NORTHWARD. GIVEN THE STRONG MODEL AGREEMENT...RELIED UPON THE
HIGHER RESOLVING NAM OVER THE GREAT LAKES AND HIGHER TERRAIN WHERE
GENERAL SUPPORT ALSO EXISTED FROM OTHER GUIDANCE...ALONG WITH
CONTRIBUTIONS FROM THE GFS/ECMWF/UKMET/SREF MEAN.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

...WEST COAST/INTERMOUNTAIN WEST/CENTRAL-SOUTHERN ROCKIES...

MODELS MAINTAIN GOOD CONTINUITY WITH PRIOR RUNS AND SHOW GOOD
AGREEMENT OVERALL WITH ONLY A SLIGHT SLOWING NOTED IN THE LATEST
GUIDANCE WITH THE CYCLONE CURRENTLY ORGANIZING OFF THE PACIFIC
NORTHWEST COAST AS IT MOVES ACROSS THE REGION. THUS...THE
FORECAST PHILOSOPHY REMAINS CONSISTENT WITH EARLIER
ISSUANCES...GENERALLY RELYING UPON A 3 TO 4-WAY MODEL BLEND TO
ADDRESS SYSTEM UNCERTAINTIES TO DERIVE THE PROBABILITIES...WITH
THE THE NAM USED MOST IN THE MOUNTAINS BUT STILL COMBINED WITH THE
OTHER SOLUTIONS. THE LOW'S PATH SUPPORTS THE HIGHER SNOW
PROBABILITIES OVER THE SIERRAS/INTERMOUNTAIN WEST INCLUDING THE
WASATCH...ALONG WITH THE MOGOLLON RIM AND SAN JUAN MOUNTAINS.
CONFIDENCE IN THE FORECAST IS ABOVE AVERAGE GIVEN THE NARROW MODEL
SPREAD.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

...PLAINS AND MIDDLE MISSISSIPPI/OHIO RIVER VALLEYS...

HEAVY SNOW IS LIKELY TO DEVELOP FROM KANSAS NORTHEASTWARD
BEGINNING WEDNESDAY AS THE STRONG CYCLONE CROSSING THE SOUTHWEST
STRENGTHENS IN THE LEE OF THE ROCKIES AND BEGINS TO INCORPORATE
LEVELS OF MOISTURE AND INSTABILITY WITHIN A STRONG BAROCLINIC
ENVIRONMENT MORE INDICATIVE OF EARLY SPRING PATTERN THAN LATE
WINTER. IN ANY EVENT...MODEL GUIDANCE IS GENERALLY WELL-CLUSTERED
TRACKING THE LOW FROM SOUTHEAST COLORADO/OK PANHANDLE TOWARD IOWA
BY THURSDAY NIGHT...WITH THE GFS A LITTLE SLOWER AND WEAKER
COMPARED TO THE SLIGHTLY STRONGER/NORTHWARD NAM/ECMWF. OVERALL
HOWEVER...THE SOLUTION ENVELOPE IS RELATIVELY NARROW FOR A 48-72
HR EVENT. MODEL DETAILS ARE A BIT TRICKY THOUGH...WITH THE NAM
SUSPICIOUSLY WEAK WITH CONVECTION FORMING ALONG THE GULF COAST
REGION...WHICH MAY NEGATIVELY IMPACT ITS FORECASTS OF
TEMPERATURE/MOISTURE FARTHER NORTH AND IN VICINITY OF THE
RAIN/SNOW LINE. THUS...RELIED MORE UPON THE BETTER AGREEING
GFS/ECMWF FOR INTENSITY WITHIN THE COLD SECTOR BUT LEANED MORE
TOWARD THE SLOW SIDE OF THE SCALE GIVEN MODEL RECENT TRENDS IN
THAT DIRECTION. THE RESULT IS A LARGE REGION OF MODERATE
PROBABILITIES OF A FOOT OR MORE OF SNOW OVER NORTHERN
KANSAS...WITH A BROAD REGION OF MODERATE TO HIGH PROBABILITIES OF
4 AND 8 INCHES OF SNOW SURROUNDING IT. THE SOUTHERN TO
SOUTHEASTERN PERIPHERY OF THE SNOW AXIS WILL LIKELY BEGIN OR
TRANSITION THROUGH SLEET...SOME OF WHICH COULD BE HEAVY AND
POSSIBLY CONVECTIVE IN ORIGIN IF MODEL FORECAST SOUNDINGS ARE
CORRECT.

SIGNIFICANT ACCUMULATIONS OF FREEZING RAIN ARE ALSO LIKELY WITH
THIS EVENT...WITH A CONSENSUS APPROACH OF THE ABOVE MENTIONS
SOLUTIONS SUGGESTING THAT NORTHERN ARKANSAS/SOUTHERN
MISSOURI...POSSIBLY EXTENDING INTO WESTERN PORTIONS OF THE OHIO
VALLEY BY THURSDAY NIGHT...ARE THE MOST LIKELY AREAS. NAM AND GFS
FORECAST SOUNDINGS SHOW A CLASSIC FREEZING RAIN SOUNDING FORMING...
PARTICULARLY OVER NORTHERN/CENTRAL ARKANSAS WEDNESDAY NIGHT/EARLY
THURSDAY...
WITH THE MODELS ALSO AGREEING THAT A SECONDARY LOW WILL DEVELOP
OVER LOUISIANA...THUS HELPING THE FLOW TO REMAIN SUFFICIENTLY
BACKED TO PROLONG THE EVENT. GIVEN THE FORECAST SOUNDINGS ALONG
WITH THE FAVORABLE LARGER-SCALE SYNOPTIC ENVIRONMENT AND VERY
MOIST PROFILES...MODERATE PROBABILITIES OF RECEIVING AT LEAST 0.25
INCHES OF FREEZING RAIN WERE INCLUDED OVER NORTHERN ARKANSAS AND
SOUTHERN MISSOURI...WITH DETERMINISTIC VALUES PEAKING AROUND 0.50
INCHES. LOW PROBABILITIES OF ICE ALSO EXTEND INTO THE OHIO VALLEY
AND PORTIONS OF THE CENTRAL APPALACHIANS...WITH THE FINAL
PROBABILISTIC ICE VALUES NUDGED SOUTHWARD AND AWAY FROM THE SREF
MEMBERS WHICH SEEMED TOO FAST TO EJECT THE LOW OUT OF THE
PLAINS...ESPECIALLY AS THE MOISTURE SHIELD ENTERED THE OHIO
VALLEY.

JAMES

The attachment 02192013 07Z HPC lowtrack_ensembles.gif is no longer available

[srainhoutx]

I also wanted to take a moment to look a bit further out into the day 6-10 range this morning. There is growing consensus that we are moving toward a cold and stormy pattern across the Lower 48 as we head toward the late February time frame. A very noisy sub tropical jet and a blocking pattern over the NW Atlantic that has been absent this Winter is now developing. While the Pacific pattern transitions to that of a large High Pressure Ridge from Hawaii to the Gulf of Alaska, storm systems will ride up and over that Pacific Ridge and drop S into the Desert SW and travel further South as the march East with a large blocking High over Eastern Canada. What we will need to monitor in the days ahead is the development of low pressure over the NW Gulf as embedded short wave energy ride the noisy sub tropical jet and the 500mb upper low track shift a bit further S across the Southern Plains/Lower Mississippi Valley before turning NE along the East Coast. Such a somewhat similar 500mb pattern in past years has brought some noteworthy Winter Storms such as the March 1993 Super Storm and a powerful Nor’easter that impacted the East Coast in 2001. We will see.

00Z Euro Ensembles:

The attachment 02192013 00Z Euro Ensembles 00zECMWFENS500mbHeightAnomalyNH240.gif is no longer available

00Z GEFS:

00Z NAEFS:

[srainhoutx]

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
1049 AM EST TUE FEB 19 2013

VALID 12Z FRI FEB 22 2013 - 12Z TUE FEB 26 2013

...WET AND ACTIVE WEATHER PATTERN TO CONTINUE ACROSS THE US...

OVERVIEW...
MANUAL SURFACE GRAPHICS CONTINUE WITH THE PROGRESSION OF SYSTEMS
ACROSS THE MIDWEST AND EAST COAST. THE 19/00Z ENSEMBLE GUIDANCE
WAS BEST REPRESENTED BY THE ECMWF THROUGH DAY 5...WHICH REMAINS ON
THE SLIGHTLY SLOWER SIDE OF THE SPREAD VS THE CANADIAN/GEFS AND
NAEFS. SPREAD ENLARGES ACROSS THE EAST PACIFIC AND DOWNWIND INTO
THE CENTRAL PLAINS/GREAT LAKES FOR DAYS 6-7...AND MUCH OF IT...IS
TIED TO TIMING INDIVIDUAL SHORTWAVE STRENGTH EJECTING OUT OF THE
CENTRAL ROCKIES.

SYSTEM RELEVANCE...
THE DAY 3 SYSTEM TRACKING ACROSS THE CENTRAL STATES REMAINED ON
TRACK WITH LITTLE VARIATION FROM CONTINUITY.
DOWNSTREAM...CONDITIONS REMAINED FAVORABLE FOR SECONDARY
CYCLOGENESIS ALONG THE CAROLINA COAST/PIEDMONT REGION AND BROAD
ISENTROPIC LIFT/ UPGLIDE OF GULF MOISTURE INTO THE MID- TO
UPPER-LEVEL CIRCULATION POSITIONED INVOF THE GREAT LAKES.

THE DAY 4-5 SYSTEM EMERGING OFF THE CAROLINA COAST REMAINS IN A
FAVORABLE POSITION FOR INTENSIFICATION BETWEEN SATURDAY NIGHT AND
SUNDAY MORNING AS IT TRACK NORTHEASTWARD ALONG THE EASTERN
SEABOARD. TO FULLY RESPECT THE 19/00Z GEFS/GFS SOLUTION WOULD BE
TO SWIFTLY EJECT THE SYSTEM AWAY FROM THE NORTHEAST. AT THIS
POINT...THE UPSTREAM PATTERN IS DRIVING THIS SOLUTION AND RECENT
TRENDS IN THE GFS/ECMWF AND CANADIAN SUGGEST THERE WILL BE A
SLOWER PROGRESSION OF THE PATTERN THAN WHAT THE 19/00Z GFS
PACKAGES SUGGEST.

THE DAY 4-5 SYSTEM INTENSIFYING OUT WEST IN THE GREAT
BASIN...APPEARS TO EJECT SEVERAL SHORTWAVES NORTHEASTWARD INTO THE
CENTRAL PLAINS...AND THE DETERMINISTIC THICKNESS/TEMPERATURE
FIELDS DO NOT SUPPORT A 'LONE' OR SINGLE (VERTICALLY-STACKED)
CYCLONE. RATHER A COMPLEX 'TROWAL'...AND TRIPLE POINT LOW
STRUCTURE. ONE THAT EJECTS AND INTENSIFIES AN ADDITIONAL SHORTWAVE
AND SURFACE WAVE ACROSS THE SOUTHEAST AND INTO THE CAROLINAS
BETWEEN DAYS 6-7. THE 'TROWAL' STRUCTURE IS DEPICTED ON THE
SURFACE GRAPHICS AS A COMPLEX OCCLUSION...WITH THE PRIMARY WAVE
EMERGING ACROSS THE PIEDMONT REPRESENTING SOMETHING THAT PATTERNS
ITSELF MORE LIKE A NEGATIVELY-TILTED TROUGH.

VOJTESAK

[mcheer23]

Question, how bad is the weather looking in the Mobile, Alabama area on Thursday

[srainhoutx]

The 12Z Euro/Canadian have trended a bit further S with the 500mb upper low passing over New Mexico and the Texas Panhandle and then NE. It also appears the GFS/UKMet may be a tad too progressive and a bit slower movement suggested by the Euro/CMC may bode a bit better for severe chances across Texas into Louisiana/Mississippi. One thing that is looking likely, one heck of a snow and ice event is in store across Kansas/Nebraska/Iowa and South Dakota on E.

[srainhoutx]

Without discounting the events of tomorrow and Thursday into early next week, the signals continue to grow that this stormy and 'colder' pattern may well linger as we end February.

12Z Euro Hour 216:

The attachment 02192013 12Z Euro 12zeuro500mbHeightAnomalyNA216.gif is no longer available

12Z Euro Hour 240:

[srainhoutx]

Winter Storm RECON has again been tasked and the G-IV will fly back to Alaska for the next potential mission.

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1230 PM EST TUE 19 FEBRUARY 2013
SUBJECT: WINTER STORM PLAN OF THE DAY (WSPOD)
VALID 20/1100Z TO 21/1100Z FEBRUARY 2013
WSPOD NUMBER.....12-081

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY: POSSIBLE ALASKAN
TRACK P22/ DROP 6 (57.0N 178.0W)/ 22/0000Z

[srainhoutx]

Updated Short Range Forecast from the HPC paints a very stormy outlook for much of the Lower 48...

SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
358 PM EST TUE FEB 19 2013

VALID 00Z WED FEB 20 2013 - 00Z FRI FEB 22 2013

...HEAVY SNOW POSSIBLE OVER PARTS OF THE CENTRAL PLAINS...

...FREEZING RAIN AND SLEET POSSIBLE FOR PARTS OF THE LOWER/MIDDLE
MISSISSIPPI VALLEY...

...TEMPERATURES WILL BE 10 TO 20 DEGREES BELOW AVERAGE FROM EAST
OF THE ROCKIES TO WEST OF THE APPALACHIANS AND OVER THE
SOUTHWEST...

A STORM OVER THE GREAT BASIN WILL MOVE EASTWARD TO THE
SOUTHERN/CENTRAL PLAINS BY THURSDAY. THE SYSTEM WILL PRODUCE SNOW
FROM THE NORTHERN ROCKIES/GREAT BASIN INTO THE HIGHER ELEVATIONS
OF OREGON/CALIFORNIA THAT WILL MOVE TO THE CENTRAL ROCKIES/GREAT
BASIN AND THE SOUTHWEST ON WEDNESDAY. THE SNOW WILL END OVER THE
GREAT BASIN/SOUTHWEST BY THURSDAY MORNING. RAIN WILL DEVELOP OVER
PARTS OF THE PACIFIC NORTHWEST COAST TO SOUTHERN CALIFORNIA COAST
... ENDING BY WEDNESDAY EVENING.

OVERNIGHT TUESDAY ... MOISTURE COMING OUT OF THE GULF OF MEXICO
WILL MOVE NORTHWARD OVER THE SOUTHERN/CENTRAL PLAINS AND OVER
PARTS OF THE LOWER MISSISSIPPI VALLEY BY THURSDAY. SHOWERS AND
THUNDERSTORMS WILL DEVELOP OVER THE LOWER RIO GRANDE VALLEY
EXPANDING INTO THE SOUTHERN PLAINS ON WEDNESDAY. THE SHOWERS AND
THUNDERSTORMS WITH HEAVY RAIN WILL DEVELOP OVER PARTS OF EASTERN
TEXAS/LOWER MISSISSIPPI VALLEY ON THURSDAY. RAIN WILL ALSO
DEVELOP OVER PARTS OF THE SOUTHERN PLAINS MOVING INTO PARTS OF THE
LOWER MISSISSIPPI VALLEY ALSO ON THURSDAY. IN ADDITION ... SNOW
WILL DEVELOP OVER PARTS OF THE SOUTHERN PLAINS ON TUESDAY MORNING
... EXPANDING INTO THE CENTRAL/NORTHERN PLAINS WEDNESDAY EVENING
INTO THURSDAY. HEAVY SNOW WILL DEVELOP OVER PARTS OF THE CENTRAL
PLAINS/MIDDLE MISSISSIPPI VALLEY ON THURSDAY. FURTHERMORE ...
FREEZING RAIN AND SLEET WILL DEVELOP OVER PARTS OF THE
LOWER/MIDDLE MISSISSIPPI VALLEY WEDNESDAY NIGHT INTO THURSDAY.

MEANWHILE ... A STORM OVER THE GREAT LAKES WILL MOVE INTO
SOUTHEASTERN CANADA BY THURSDAY. RAIN OVER THE MID-ATLANTIC
COAST/SOUTHERN NEW ENGLAND WILL MOVE OFF INTO THE ATLANTIC
OVERNIGHT TUESDAY. THE SYSTEM WILL ALSO PRODUCE SNOW OVER PARTS
OF THE INTERIOR NORTHEAST BECOMING HEAVY SNOW OVER PARTS OF
NORTHERN MAINE ON WEDNESDAY MORNING. LIGHT SNOW WILL LINGER OVER
PARTS OF NORTHERN NEW ENGLAND BY THURSDAY. ALSO ... LAKE EFFECT
SNOW WILL DEVELOP OVER THE GREAT LAKES THROUGH LATE WEDNESDAY
NIGHT.

DYING FRONTS AND UPPER-LEVEL ENERGY WILL MOVE INLAND OVER THE
NORTH PACIFIC WEDNESDAY NIGHT INTO THURSDAY PRODUCING COASTAL RAIN
AND HIGHER ELEVATION SNOW ... WITH THE SNOW MOVING INTO PARTS OF
THE NORTHERN ROCKIES ON THURSDAY.


ZIEGENFELDER

[srainhoutx]

Morning e-mail from Jeff:

Next upper level storm system moving toward the state this morning.

Fast moving upper level pattern resulting in rapid day to day weather changes across the region. Mid and upper level cloud decks have spread across the area overnight as the lead short wave ahead of the main upper trough along the CA coast ejects over TX this morning. Showers have developed over much of northern into eastern TX with this feature. At the surface the old cold frontal boundary is breaking down over the Gulf of Mexico and starting to return northward as a warm front as surface pressures lower over NW TX. Will start to see cloud bases lower this morning into the afternoon hours and lift of the warm moist Gulf air mass over the surface cold dome continues to saturate the low level air mass from the top down. Fairly dry low level ESE flow is in progress along the upper TX coast this morning and his will result in much of the initial rainfall evaporating before reaching the ground. By mid to late afternoon, the low levels should become saturated with widespread drizzle and light rain developing and spreading northward out of the Gulf of Mexico.

Warm front will move inland tonight, but believe that the “juicy” tropical air mass will south of the region. While some sort of a warm front swings north across the region overnight, instability will be lacking although very strong shear will be in place. Lift from the main upper level trough and surface cold front arrives into the region in the 400-600am and expect an increase in showers and thunderstorms from west to east during the morning hours on Thursday. As for the severe potential, the lack of instability and ever so close mid level capping over the coastal bend and S TX has me favoring areas NE of a line from College Station to Conroe to Liberty to High Island for any isolated severe threats. While SPC is further SW with their outlook area, capping could be an issue for those areas SW of the Houston metro area. Main threat appears to be large hail and wind damage although would not rule out a tornado if any discrete cells can root near the surface and utilize the very favorable low level shear environment. Current thinking is that any tornado threat will be near/along the warm frontal boundary which should be very near our northern set of counties from Huntsville to Lake Livingston and with any cells that can develop ahead of the main line of storms. Think the main line of storms will be a broken thin band with the heaviest and more solid part of the line passing along and north of I-10.

This system will exit east late Thursday, but the surface cold front slows and stalls near the coast. With an active sub-tropical jet overhead a few light showers may linger near the coastal locations into Friday morning before stronger surface high pressure forces the boundary offshore on Friday.

Fast moving flow aloft has the next system into the area by late Sunday/Monday but moisture return is looking limited with the fast moving nature and winds only turning off the Gulf on early Sunday giving a small window for moisture to move northward.

Severe Weather Outlook for Thursday:

[srainhoutx]

While we are watching the severe potential developing later tonight into tomorrow across Texas and Louisiana, there continues to be strong signals via the Global operational and ensemble computer guidance that a very active southern stream Winter Storm will develop to our W early next week and travel much further S than we have seen so far this winter season. As we have seen so far this season, the storm track has been that of systems developing in the Desert SW and traversing ENE into the Plains and Mid West. The upper air pattern has changed across the Northern Hemisphere to that of a strong blocking pattern over the NW Atlantic extending E into Eastern Canada. That ingredient has been missing all winter and is now firmly established. This West based –NAO regime with a –AO and PNA pattern does bode well for a southern suppressed storm track. Another ingredient that is noteworthy is the convective activity across the Eastern Pacific that suggests a very noisy sub tropical jet. It appears that the guidance is latching on to such a scenario and agreement with the computer models lends credibility to closely monitoring the trends over the next several days. NOAA G-IV Winter Recon departed Hawaii yesterday afternoon and made several drops last night en route to Anchorage and will fly again tonight over the NE Pacific. This additional data will likely aid the computer models as this progressive pattern continues as we head toward the end of February.

00Z Operational European Model:

00Z NAEFS (North American (NCEP/Canadian) Ensemble):

[srainhoutx]

While the NAM/GFS solutions today are slightly less favorable for severe weather in Houston, threat further E for our neighbors in Louisiana appear to be increasing. With some daytime heating and a weakening cap, the potential for rotating super cells may well be an issue ahead of the advancing cold front/squall line during the mid to afternoon hours tomorrow E of the Sabine River. Also looking a bit further out, the GFS continues to advertise a potent Southern Storm developing across the Southern Rockies dropping S into Texas for the mid next week time frame. Additional Winter Storm RECON has been tasked to fly from Anchorage over the NE Pacific as well.

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1045 AM EST WED 20 FEBRUARY 2013
SUBJECT: WINTER STORM PLAN OF THE DAY (WSPOD)
VALID 21/1100Z TO 22/1100Z FEBRUARY 2013
WSPOD NUMBER.....12-082

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

II. PACIFIC REQUIREMENTS
1. FLIGHT ONE -- NOAA 49 --
A. P22/ DROP 6 (57.0N 178.0W)/ 22/0000Z
B NOAA9 15WSC TRACK22
C. 21/1930Z
D. 11 DROPS ON TRACK AS PUBLISHED
E. 41,000 TO 45,000 FT/ 22/0600Z

2. OUTLOOK FOR SUCCEEDING DAY: POSSIBLE TRACK 23
A. P-23/ DROP 8 (47.0N 175.0W)/ 23/0000)
3. REMARKS: TRACK P-14 MODIFIED WILL BE FLOWN
TODAY AS DETAILED ON WSPOD 12-081 AMENDED.

[Belmer]

I remember a few days ago models were showing a few inches of snow for Oklahoma and I know some were questioning it because of a strong South flow and temps would be too warm. Well looky at what we have this morning in Oklahoma.
Round of applause to the models.

[wxman666]

SPC DAY 2 Expands slight risk to cover the majority, if not all of SE TX.



DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1119 AM CST WED FEB 20 2013

VALID 211200Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SERN TX INTO THE LOWER
MS VALLEY...

...SERN TX/LOWER MS VALLEY...

SWRN U.S. UPPER LOW IS EXPECTED TO EJECT INTO THE SRN HIGH PLAINS
EARLY IN THE DAY2 PERIOD BEFORE LIFTING INTO WRN IA LATE. 150-180M
12HR HEIGHT FALLS WILL SPREAD ACROSS THE CNTRL PLAINS WITH SRN
FRINGES OF LARGER SCALE FORCING EXPECTED TO EXTEND TOWARD THE I-20
CORRIDOR. WITH SFC RIDGING STUBBORNLY RETREATING ACROSS THE MS
VALLEY IT APPEARS THE NWD ADVANCE OF MARITIME TROPICAL AIR WILL BE
LIMITED TO PORTIONS OF THE WRN GULF BASIN AND NRN EXTENT OF MODIFIED
GULF AIRMASS SHOULD SPREAD INLAND ACROSS SCNTRL/SERN TX AHEAD OF SFC
FRONT.

EARLY IN THE PERIOD A STRONG CAP WILL BE IN PLACE ACROSS SCNTRL TX
WHILE LOW LEVEL WARM ADVECTION INTENSIFIES BENEATH LLJ ALONG WRN
FRINGE OF AFOREMENTIONED RETREATING ANTICYCLONE. THIS SHOULD INDUCE
CONSIDERABLE AMOUNT OF ELEVATED CONVECTION ALONG THE RED RIVER WHERE
MUCAPE COULD APPROACH 1000 J/KG IF LIFTING PARCELS NEAR 850MB. HAIL
MAY ACCOMPANY THIS ACTIVITY AS IT SPREADS/DEVELOPS EWD TOWARD THE
ARKLATEX BY MID DAY. WITH TIME LOW LEVEL MOISTURE SHOULD INCREASE
ACROSS THE UPPER TX COAST/LA SUCH THAT NEAR-SFC BASED PARCELS WILL
BE MINIMALLY INHIBITED. THIS WILL BE THE PRIMARY CONCERN FOR
POTENTIAL SEVERE THUNDERSTORM DEVELOPMENT DURING THE PERIOD IF
DISCRETE SUPERCELLS CAN EVOLVE WITHIN THE WEAKER LAPSE RATE/LIMITED
BUOYANCY ENVIRONMENT. GIVEN THAT THE STRONGEST FORCING WILL SPREAD
WELL NORTH OF THIS REGION LOW LEVEL WARM ADVECTION AND BOUNDARY
LAYER MOISTENING WILL BE THE GREATEST CONTRIBUTORS TO POTENTIAL
ROBUST CONVECTION. IT/S NOT ENTIRELY CLEAR TO THE QUALITY OF
MOISTENING THAT CAN OCCUR ACROSS THE EVOLVING WARM SECTOR BUT
FORECAST NAM PROFILES SUGGEST MID 60S SFC DEW POINTS COULD RETURN
WHILE MUCAPE MAY INCREASE TO ROUGHLY 1000 J/KG. SHEAR PROFILES
CERTAINLY FAVOR SUPERCELLS AND GIVEN THE WARM ADVECTION REGIME IT
WOULD SEEM LIKELY THAT DISCRETE SLIGHTLY ELEVATED STRUCTURES CAN BE
EXPECTED. TRUE WARM SECTOR SFC BASED UPDRAFTS MAY BE LIMITED TO THE
COLD FRONT WHERE LOW LEVEL SHEAR WILL BE LESS FAVORABLE FOR
TORNADOES. EVEN SO NEAR-SFC BASED STRUCTURES MAY PRODUCE ISOLATED
TORNADOES WHILE MARGINALLY SEVERE HAIL AND LOCALLY DAMAGING WINDS
COULD ALSO ACCOMPANY THE STRONGEST STORMS. THE CORRIDOR OF
STRONGEST STORMS SHOULD GRADUALLY SHIFT ACROSS THE LOWER MS VALLEY
DURING THE LATTER HALF OF THE PERIOD AS THE FRONTAL ZONE ORIENTS
ITSELF IN A SW-NE FASHION FROM THE UPPER TX COAST INTO CNTRL MS.

..DARROW.. 02/20/2013

[srainhoutx]

Some impressive analogs showing up on the CPC Super Ensemble 500mb charts for late February/early March...

[cristina99]

Kind of been MIA since it looked like winter was over for us. Sorry warm weather friends I just don't like the hot weather. I am worried about tomorrow's storms and the timing. KHOU has predicted the worst could be from as early as 5 a.m. to past 9 or 10. Can someone give their guestimate as to when the worst will hit? Thanks.

[sambucol]

Kind of been MIA since it looked like winter was over for us. Sorry warm weather friends I just don't like the hot weather. I am worried about tomorrow's storms and the timing. KHOU has predicted the worst could be from as early as 5 a.m. to past 9 or 10. Can someone give their guestimate as to when the worst will hit? Thanks.

Is the bad weather for in the morning still in the forecast? If so, I'm literally going to be outside in it.