Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA

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285
FXUS64 KLIX 011409
AFDLIX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
809 AM CST SUN FEB 1 2015

...SOUNDING DISCUSSION...

IMPRESSIVE MOISTENING OF THE ATMOSPHERE HAS OCCURRED OVER THE
CENTRAL GULF COAST THE LAST 12 HOURS AS THE PRECIPITABLE WATER HAS
JUMPED UP TO 1.44 INCHES. THE ATMOSPHERIC COLUMN IS SATURATED FROM
3400 TO 14400 FEET. TEMPERATURES IN THE LOWEST 2600 FEET ARE HIGHER
/WARMER/ ON AVERAGE BY ABOUT 6 DEGREES CELSIUS OVER THIS LAYER
COMPARED TO YESTERDAY AT THIS TIME. THE SURFACE ITSELF IS 13 C
HIGHER /WARMER/.

THERE IS NOT MUCH IN THE WAY OF INSTABILITY WITH A LIFTED INDEX
OF 5 AND SURFACE BASED AND MIXED LAYER CAPE CALCULATED AT 0
CURRENTLY. THAT SAID...THERE IS WIND SHEAR--BOTH DIRECTION AND
SPEED. WIND PROFILE IS TYPICAL OF A WARM ADVECTION REGIME
/VEERING/. WINDS ARE FROM THE SOUTHEAST AT 0-20 KNOTS NEAR THE
SURFACE ROTATING TO THE FROM THE SOUTHWEST AT 20 INCREASING TO 65
KNOTS IN THE MID-LEVELS AND FROM THE WEST IN THE UPPER LEVELS
WITH A PEAK WIND SPEED OF 107 KNOTS. 0-1 KM SRH IS OVER 300 M2/S2
AND 0-3 KM SRH IS NEARING 400 M2/S2. SPC DOES HAVE US IN MARGINAL
RISK FOR SEVERE WEATHER. THERE ARE LIMITING FACTORS THOUGH TODAY.
THERE IS ONLY ONE MAIN AREA OF CONVERGENCE...WHICH WILL BE ALONG
THE COLD FRONT. ANOTHER LIMITING FACTOR IS THE LACK OF SUNSHINE
AND THEREBY INSTABILITY. FORECAST SOUNDINGS SHOW LITTLE IF ANY
INSTABILITY DEVELOPING. WE WILL WATCH AS THE FRONT APPROACHES AND
MONITOR TRENDS IN CLOUD COVER THROUGHOUT THE DAY FOR ANY POSSIBLE
SEVERE WEATHER.

12Z BALLOON INFO: THIS MORNING/S FLIGHT LASTED 124 MINUTES AND
WENT 91 MILES DOWNRANGE BEFORE BURSTING AT A HEIGHT OF 21 MILES
ABOVE THE GROUND NEAR BIG CREEK LAKE AL JUST WEST OF MOBILE.

ANSORGE

&&

.PREV DISCUSSION... /ISSUED 417 AM CST SUN FEB 1 2015/

SHORT TERM...MOISTURE HAS BEEN INCREASING QUICKLY ALONG WITH LIFT
OVER THE AREA AND THUS AFTER 6Z THE RADAR HAS BECOME FAR MORE
ACTIVE. VERY LGT RAIN HAS ALREADY OCCURRED WEST OF 55 AND SOUTH OF 10
AND THIS ACTIVITY SHOULD CONTINUE TO INCREASE IN COVERAGE AND
INTENSITY THROUGH THE MRNG.

NOT MUCH HAS CHANGED IN THE FCST AS WE ARE STILL LOOKING AT MULTIPLE
SYSTEMS IMPACTING THE REGION OVER THE NEXT WEEK. FIRST ONE IS
ALREADY OCCURRING AND IS CHARACTERIZED BY TWO SEPARATE DISTURBANCES.
THE SECOND SYSTEM WILL BE WHEN THE BAJA LOW FINALLY LIFTS OUT ACROSS
THE REGION MID WEEK.

FIRST TODAY AND TONIGHT WE WILL SEE NUM TO WIDESPREAD SHRA AND EVEN
A FEW EMBEDDED TSRA(MAINLY LATE THIS AFTN AND THIS EVNG). AS
MENTIONED EARLIER ACTIVITY HAS BEEN INCREASING THROUGH THE OVERNIGHT
HRS AS BROAD LIFT HAS INCREASED OVER THE REGION. FIRST FOCUSED
DISTURBANCE IS A PIECE OF ENERGY THAT HAS DETACHED FROM THE BAJA LOW
AND AT 8Z WAS MOVING THROUGH SRN AND CNTRL TX. THIS WILL QUICKLY
PUSH THROUGH THE LOWER MS VALLEY THIS MRNG AND LIKELY BE EAST OF THE
AREA BY 18Z. MOISTURE HAS BEEN INCREASING AND WILL CONTINUE TO DO
SO. AT THE SAME TIME AN H85 THETA E RIDGE WILL BE DRAPED/MOVING
ACROSS THE SRN/SERN HALF OF THE CWA THROUGH THE MORNING. THIS WILL
LIKELY BE WHERE THE GREATEST COV AND INTENSITY OF RAIN WILL OCCUR
BUT BY MIDDAY SHRA WILL LIKELY TAPER OFF BECOMING MORE SCT POSSIBLY
EVEN ISLTD WITH THE FOCUS SHIFTING TO THE NWRN HALF OF THE CWA.

THIS AFTN AND EVNG THE SECOND AND MORE SIGNIFICANT FEATURES WILL
IMPACT THE REGION. AS MENTIONED THE LAST FEW DAYS A STRONG NRN
STREAM S/W WILL CONTINUE TO DIG SE. AT 8Z THIS DISTURBANCE WAS
MOVING THROUGH THE HIGH PLAINS AND ENTERING THE CNTRL PLAINS. AT THE
SAME TIME A SFC LOW WAS BEGINNING TO TAKE SHAPE OVER KS. THE S/W
WILL CONTINUE TO WORK SE THROUGH THE DAY EVENTUALLY INTO THE UPPER
PORTIONS OF THE LOWER MS VALLEY TONIGHT WHILE THE SFC LOW WILL
DEEPEN AND PUSH EAST THROUGH THE MID MS VALLEY AND INTO THE OH
VALLEY. A TRAILING COLD FRONT WILL SWEEP THROUGH THE SRN PLAINS AND
INTO THE LOWER MS VALLEY PUSHING ALL THE WAY INTO THE GULF WELL
BEFORE 12Z MON. ALL OF THIS WILL PROVIDE MORE THAN ENOUGH SUPPORT
FOR RAIN ACROSS THE REGION WITH THE GREATEST CHANCE OF SEEING RAIN
ACROSS THE NRN HALF OF THE CWA. AS FOR THE CHANCE OF TSRA...MAYBE
EVEN A STRONG ONE OR TWO...THE THREAT DOESNT LOOK GREAT BUT IT IS
NON-ZERO. OVERALL INSTABILITY WILL BE GREATLY LACKING...LL
CONVERGENCE WILL BE WEAK WITH THE EXCEPTION OF THE COLD FRONT...AND
THE BETTER MID/UPPER LVL SUPPORT WILL BE POST FRONTAL. THAT SAID MID
LVL LAPSE RATES ARENT TOO SHABBY AT 6-6.5 C/KM...0-6KM BULK SHEAR
WILL BE AROUND 50-60 KTS AND THERE WILL BE SOME MID LVL FLOW AROUND
50-60KTS AS WELL. THIS COULD PROVIDE ENOUGH SUPPORT TO GET A FEW
STORMS TO OVERACHIEVE PROVIDING A SMALL RISK OF DAMAGING WINDS.
AGAIN NOT OVERLY IMPRESSED BUT THE RISK IS NON-ZERO.

RAIN WILL START TO COME TO AN END AFTER MIDNIGHT AS THE COLD FRONT
SWEEPS THROUGH. ONCE IT DOES MUCH COLDER AND DRIER AIR WILL SURGE
INTO THE AREA. H925 TEMPS STILL LOOK LIKE THEY WILL DROP TO AROUND
0-3C. WHEN THIS IS MIXED DOWN TO THE SFC IT SHOULD YIELD TEMPS IN
THE MID 40S TO LOWER 50S AND THAT SEEMS ABOUT RIGHT AS BOTH SFC
MOISTURE FROM RECENT RAIN AND BREEZY CONDITIONS WILL KEEP THAT SUPER
ADIABATIC SFC/SKIN LAYER FROM DEVELOPING. WITH TEMPS THAT LOW DURING
THE DAY IT WILL SET THE STAGE FOR A COLD NIGHT. HIGH PRESSURE WILL
CONTINUE TO BUILD INTO THE REGION AND SETTLE RIGHT OVER THE AREA MON
NIGHT/TUE MRNG. WITH THAT WINDS SHOULD DECOUPLE...EVEN LL WINDS WILL
BE LGT. DEWPOINTS WILL BE QUIET LOW...POSSIBLY IN THE LOWER TO MID
20S...AND SKIES SHOULD BE CLEAR. THIS SHOULD ALLOW FOR MRNG LOWS TUE
TO RANGE FROM THE UPPER 20S IN SWRN MS TO MID UPPER 30S ACROSS
COASTAL SELA. THE FEW THINGS THAT COULD KEEP THE REGION FROM COOLING
AS MUCH AS FCST WILL BE RESIDUAL GROUND MOISTURE FROM SUN/SUN NIGHTS
RAINS ALONG WITH WEAK WAA IN THE LL ABV THE SFC. /CAB/

LONG TERM...MEDIUM RANGE MDLS CONTINUE TO STRUGGLE WITH CONSISTENCY
AND CONTINUITY. THE GFS HAS NOW SLOWED UP SIGNIFICANTLY FROM
YESTERDAYS 00Z RUN AND THE ECMWF IS NOW MUCH FASTER. THIS IS NOT
BODING WELL FOR CONFIDENCE IN THE FCST. THE GEM IS RIGHT IN THE
MIDDLE OF THE TWO AND THE GFES IS IN BETTER AGREEMENT WITH THE GFS
TIMING WISE. OVERALL CONFIDENCE IS LOW WITH RESPECT TO TIMING BUT
HIGH THAT WE WILL GET SOME DECENT RAIN SOMETIME BETWEEN TUE NIGHT AND
THU. WITH THIS UNCERTAINTY WILL STICK WITH A BLEND OF THE MDLS AND
NOT LEAN IN FAVOR OF A SPECIFIC MDL.

THE MAIN PROTAGONIST WILL BE THE BAJA LOW EJECTING OUT ACROSS THE
REGION. THE QUESTIONS ARE HOW FAST DOES THIS OCCUR AND WHAT ACTUALLY
KICKS THIS LOW OUT OF THE BAJA. LOOKING ACROSS THE PAC LARGE LOW
JUST SOUTH OF THE ALEUTIANS WILL CONTINUE TO SPIN THERE THROUGH
PRETTY MUCH THE ENTIRE FCST BUT THERE WILL BE A LOT OF ENERGY MOVING
ACROSS THE CNTRL PAC TRYING TO BREAK DOWN THE RIDGE OVER THE ERN PAC
JUST WEST OF THE BAJA LOW. THIS WILL TAKE SOME TIME WHICH IS WHY THE
BAJA LOW WILL STAY IN PLACE UNTIL MON NIGHT. TYPICALLY THIS IS A
SLOW PROCESS AND B/C OF THAT I WANT TO LEAN TWRDS THE SLOWER GFS BUT
THIS IS SIGNIFICANTLY SLOWER THAN PREV RUNS. IN FACT THE GFS TRIES
TO KEEP MUCH OF THE RAIN OUT OF THE AREA UNTIL LATE WED. EVEN THE
EURO WHEN IT WAS THE SLOWEST MDL HAD RAIN THROUGH MUCH OF THE DAY
WED. AS MENTIONED EARLIER WILL GO WITH A BLEND OF THE MDLS. THE BAJA
LOW SHOULD MOVE ACROSS MEXICO AND OPEN UP AS IT MOVES INTO TX LATE
TUE NIGHT/EARLY WED AND ACROSS THE GULF COAST STATES WED AND THU. AT
THE SFC STILL LOOKING FOR CYCLOGENESIS IN THE NWRN GULF WITH THIS
LOW MOVING EAST ACROSS THE NRN GULF AND EVENTUALLY INTO FL LATE
THU/EARLY FRI. THIS WILL LEAD TO NUM TO WIDESPREAD SHRA WITH LGT
RAIN POSSIBLY AS EARLY AS OVERNIGHT TUE NIGHT. BULK OF THE RAIN
SHOULD OCCUR WED AND/OR WED NIGHT. NOT ANTICIPATING ANY TSRA AS WE
WILL BE IN THE COLD SECTOR.

RAIN WILL COME TO AND END THU/THU NIGHT WITH A STRONG NRN STREAM S/W
DROPPING ACROSS THE REGION AT THE SAME TIME. THIS WILL DRIVE A
COOLER AND MUCH DRIER AIRMASS INTO THE REGION FOR FRI AND NEXT
WEEKEND. /CAB/

AVIATION...VFR CONDITIONS ARE STILL BEING OBSERVED THIS MORNING AND
WE ARE STILL ANTICIPATING CONDITIONS TO DETERIORATE THIS MORNING.
CEILINGS SHOULD BE IN THE THE MVFR TO IFR CATEGORIES AND RAIN SHOULD
SPREAD ACROSS THE AREA AND OCCASIONALLY RESTRICT VISIBILITIES
INTO THE 2 TO 3 MILE RANGE. A COLD FRONT WILL BEGIN PUSHING ACROSS
THE REGION AFTER 00Z MONDAY. 13/MH

MARINE...EXERCISE CAUTION HEADLINES WILL REMAIN IN EFFECT THROUGH
THE MID MORNING HOURS AS WINDS STILL WILL REMAIN SLIGHTLY ELEVATED
AS A SYSTEM MOVES TO THE NORTH OF THE AREA. WINDS WILL BRIEFLY RELAX
SUNDAY AFTERNOON AS A COLD FRONT APPROACHES. BEHIND THE FRONT COLD
AIR ADVECTION AND HIGH PRESSURE WILL ELEVATE WINDS INTO THE SMALL
CRAFT ADVISORY REALM. A SMALL CRAFT ADVISORY SHOULD BE ISSUED AT
SOME POINT THIS MORNING FOR TONIGHT INTO MONDAY MORNING. SURFACE
HIGH PRESSURE WILL BECOME CENTERED CLOSER TO THE AREA BY TUESDAY
ALLOWING WINDS AND WAVES TO EASE A BIT. HIGH PRESSURE WILL QUICKLY
SLIDE EAST ON WEDNESDAY AS A SURFACE LOW DEVELOPS AND TRACKS THROUGH
THE NORTHERN GULF. A STRONGER EASTERLY FLOW WILL RESUME AS A RESULT
ON WEDNESDAY. 13/MH

DECISION SUPPORT...
DSS CODE...GREEN.
DEPLOYED...NONE.
ACTIVATION...NONE.
ACTIVITIES...SLURRY SUPPORT

DECISION SUPPORT SERVICES (DSS) CODE LEGEND
GREEN  = NO WEATHER IMPACTS THAT REQUIRE ACTION
BLUE   = LONG FUSED WATCH/WARNING/ADVISORY IN EFFECT OR HIGH
         VISIBILITY EVENT
YELLOW = HEIGHTENED IMPACTS WITH SHORT FUSED
         WATCH/WARNING/ADVISORY ISSUANCES; RADAR SUPPORT
ORANGE = HIGH IMPACTS - SLIGHT TO MODERATE RISK SEVERE; NEARBY
         TROPICAL EVENTS; HAZMAT OR OTHER LARGE EPISODES
RED    = FULL ENGAGEMENT FOR MODERATE TO HIGH RISK SVR
         AND/OR DIRECT TROPICAL THREATS; EVENTS OF NATIONAL
         SIGNIFICANCE.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  69  37  46  28 /  80  80  10   0
BTR  72  39  48  31 /  80  70   0   0
ASD  71  43  50  32 /  60  70  10   0
MSY  73  45  50  37 /  60  70  10   0
GPT  68  44  51  33 /  70  70  10   0
PQL  69  45  51  31 /  70  60  10   0

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...NONE.
MS...NONE.
GM...NONE.
&&

$$







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