FXUS64 KCRP 230539 AAB
AFDCRP
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CORPUS CHRISTI TX
1139 PM CST TUE DEC 22 2009
.DISCUSSION...UPDATED FOR 06Z AVIATION DISCUSSION.
&&
.AVIATION...GENERALLY VFR CONDITIONS ACROSS THE REGION EXCEPT FOR
IFR/MVFR VSBYS ALONG THE COAST AND OVER THE VICTORIA CROSSROADS
REGION. STRENGTHENING LOW LEVEL JET WILL LEAD TO WIDESPREAD
DEVELOPMENT OF MVFR CIGS AFTER MIDNIGHT. ALSO, LOW LEVEL WIND
SHEAR WILL BE PROBLEMATIC OVERNIGHT AS 40 KNOTS OF WIND RESIDE AT
1.5K FEET. MVFR/VFR CIGS WILL PREVAIL WEDNESDAY AS A STRONG COLD
FRONT APPROACHES FROM THE NORTHEAST. THE FRONT WILL ENTER
NORTHWEST PORTIONS OF THE FORECAST AREA AROUND 03Z WEDNESDAY
EVENING THEN SURGE RAPIDLY SOUTHEAST THROUGH THE EARLY MORNING
HOURS ON THURSDAY. ISOLD/SCT RAIN SHOWERS WILL RESIDE OVER THE
EASTERN THIRD OF THE FORECAST AREA THROUGH MUCH OF THE TAF PERIOD.
&&
.PREV DISCUSSION... /ISSUED 928 PM CST TUE DEC 22 2009/
DISCUSSION...ISOLATED SHOWERS DEVELOPING OVER THE NORTHEAST
CORNER OF THE FORECAST AREA IN ASSOCIATION WITH A WEAK SHORTWAVE
TROUGH ALOFT APPROACHING FROM THE NORTHWEST. SPRINKLES/LIGHT RAIN
TO REMAIN LIMITED TO THE EASTERN QUARTER OVERNIGHT. ONLY OTHER
CONCERN FOR TONIGHT IS FOG FORMATION, ESPECIALLY ALONG THE
IMMEDIATE COAST WHERE DEW POINTS ARE SLIGHTLY EXCEEDING THE SHELF
WATER TEMPERATURE. INCREASING LOW LEVEL JET OVERNIGHT SHOULD LEAD
TO MORE OF A STRATUS PRODUCING SCENARIO WHILE LOW LEVEL MIXING
AIDS IN PREVENTING DENSE FOG FROM DEVELOPING. FORECASTS LOOK ON
TRACK AND NO UPDATE NECESSARY AT THIS TIME.
PREV DISCUSSION... /ISSUED 550 PM CST TUE DEC 22 2009/
DISCUSSION...NOTE AVIATION DISCUSSION BELOW.
AVIATION...MVFR VISIBILITIES ARE ANTICIPATED FOR THE 06Z-15Z WED
PERIOD FOLLOWED BY MVFR CEILINGS. SIGNIFICANT VERTICAL WIND SHEAR
IN THE SFC-2000FT LAYER ANTICIPATED FOR THE 09-14Z WED PERIOD
GENERALLY EAST OF US 281. ISOLD/SCT SHOWER ACTIVITY EXPECTED OVER
THE VICTORIA CROSSROADS REGION WED AFTN.
PREV DISCUSSION... /ISSUED 304 PM CST TUE DEC 22 2009/
SHORT TERM (TONIGHT THROUGH WEDNESDAY NIGHT)...A MOD TO STRONG LLJ
IN RESPONSE TO DEEPENING LOW PRESSURE ACROSS THE PLAINS...WILL
CONTINUE TO ADVECT LOW LEVEL MOISTURE INTO S TX TONIGHT THROUGH WED.
A WEAK EMBEDDED SHORT WAVE IN SW FLOW ALOFT IS PROGD TO TRACK ACROSS
S TX TONIGHT THRU WED...WHICH WILL COMBINE WITH THE INCREASING
MOISTURE AND LOW LEVEL CONVERGENCE TO PRODUCE ISOL SHRA'S TONIGHT
THRU WED MORNING. AS THE MAIN POTENT UPPER LOW APPROACHES THE
REGION THROUGH WED AFTERNOON AND THE UPPER JET NOSES ACROSS THE
AREA...RAIN CHCS WILL INCREASE...MAINLY ACROSS THE NE CWA WHERE
LEAST CAPPING...DEEPEST MOISTURE AND BEST CONVERGENCE WILL BE IN
PLACE. ISOLD TSRA'S WILL ALSO BE POSSIBLE ACROSS THE NE DUE TO
INCREASING CAPE/INSTABILITY. A STRONG COLD FRONT OF ARCTIC ORIGINS
IS PROGD TO MOVE ACROSS S TX LATE WED NIGHT. THE NAM IS A BIT
SLOWER WITH THE BDRY REACHING THE COAST AROUND 12Z WHILE THE GFS IS
MUCH FASTER AND HAS THE FRONT WELL OFFSHORE BY 12Z. WENT WITH THE
FASTER GFS GIVEN THAT THE NAM HAS BEEN GENERALLY TOO SLOW WITH
FRONTS ACROSS S TX AND GIVEN THE STRENGTH OF THE COLDFRONT...IT
SHOULD BLAST THROUGH THE AREA. STRONG N TO NW WINDS ARE EXPECTED
BEHIND THE FRONT ALONG WITH A DRIER AND COLDER AIRMASS.
AS FOR FOG POTENTIAL...AM EXPECTING THAT THE STRONG LLJ WILL PRODUCE
STRATUS AND SFC WINDS WILL REMAIN ABV 5KTS...WHICH BOTH WILL HINDER
RADIATIONAL COOLING AND THUS HINDER DENSE FOG DVLPMNT. PATCHY FOG IS
EXPECTED WHERE SKIES ARE PC. SEA FOG MAY BE MORE OF AN ISSUE TONIGHT
FOR THE BAYS AND NEARSHORE WATERS DUE TO THE RELATIVELY HIGH
DEWPOINTS OVER COOL WATERS. PATCHY FOG/SEA FOG IS EXPECTED AGAIN WED
NIGHT AHD OF THE FRONTAL BDRY.
MARINE...A MODERATE ONSHORE FLOW THIS EVENING WILL CONTINUE TO
STRENGTHEN OVERNIGHT ACROSS THE WATERS FROM 20 TO 60 NAUTICAL MILES
OFFSHORE AS LOW PRESSURE DEEPENS ACROSS THE PLAINS. WINDS ACROSS THE
NEARSHORE WATERS ARE EXPECTED TO RANGE FROM 15 TO 20 KNOTS
BUT ARE NOT EXPECTED TO STRENGTHEN MORE THAN THAT DUE TO THE COOLER
SEA WATER TEMPS MAINTAINING A STABLE ENVIRONMENT. HOWEVER...FARTHER
OFFSHORE WHERE SST ARE WARMER...STRONG WINDS JUST ABV THE SFC WILL
BE ABLE TO MIX TO THE SFC WITH WINDS INCREASING TO SCA LEVELS. SCA
CONDITIONS WILL CONTINUE ACROSS THE OFFSHORE WATERS THROUGH WED
NIGHT ALTHOUGH THERE WILL BE A BRIEF PERIOD WHERE WINDS WILL RELAX
WED EVENING. THEN WINDS STRENGTHEN OUT OF THE NW AND N AS A STRONG
COLD FRONT PUSHES OFFSHORE BY LATE WED NIGHT. PATCHY SEA FOG IS
EXPECTED ACROSS THE BAYS AND NEARSHORE WATERS TONIGHT THROUGH LATE
MORNING WED DUE TO DEWPOINTS IN THE 60S MOVING ACROSS RELATIVELY
COOLER WATER WITH TEMPS IN THE 50S. PATCHY SEA FOG IS EXPECTED ON
WED NIGHT AHD OF THE COLD FRONT. ISOLD/SCT SHRA'S WILL BE POSSIBLE
TONIGHT THROUGH WED NIGHT. ISOLD TSRA'S WILL ALSO BE POSSIBLE DURING
THE DAY WED INTO WED NIGHT.
LONG TERM (THURSDAY THROUGH TUESDAY)...UPPER PATTERN WILL EVOLVE
INTO A HIGHLY AMPLIFIED BLOCKING PATTERN WITH A DEEP TROUGH ACROSS
THE PLAINS AND STRONG RIDGING ON EITHER SIDE ACROSS THE ERN AND WRN
US. THIS WILL PROMOTE A CONTINUED COOLING TREND BEYOND THE INITIAL
COOL DOWN WITH THUR MORNINGS FRONT AS A LARGE/COLD CANADIAN SFC HIGH
DOMINATES THE ENTIRE CENTRAL PART OF THE COUNTRY FROM CANADIAN
BORDER TO GULF COAST MUCH OF THE PERIOD. HOW MUCH OF THE COLDER AIR
REACHES S TX HAS BEEN THE BIG QUESTION WITH MED RANGE MODELS
WAFFLING EACH RUN. THE UPR PATTERN SEEMS TO SUPPORT COLDER TEMPS
THAN INDICATED BY MODELS...BUT ACTUAL SFC PRESSURES ARE NOT OVERLY
IMPRESSIVE (1022 MB) AND MODELS ARE FORECASTING A RELATIVELY AVERAGE
COLD AIRMASS BY DECEMBER STANDARDS. MOST RECENT MOS HAS TRENDED
COOLER AFTER SEVERAL WARM RUNS. STILL APPEARS CLOUDS AND POSSIBLY
SOME LIGHT PRECIP WILL RETURN TO THE REGION BY SAT...AND THIS WILL
HELP LIMIT DIURNAL RANGES CHRISTMAS AND INTO THE WEEKEND. AGAIN NOT
DEVIATING TO FAR FROM MOS FORECASTS...BUT WILL HAVE TO WATCH FOR
POSSIBILITY MODELS ARE NOT HANDING THE SHALLOW COLD AIRMASS
WELL...WHICH MAY MEAN A COLDER WEEKEND COULD BE IN STORE. THAT ALL
BEING SAID WILL CONTINUE TO SHOW 30S-40S FOR LOWS WITH 50S FOR HIGHS
FRI-SUN KNOWING THAT ADDITIONAL ADJUSTMENTS ARE LIKELY THE NEXT FEW
DAYS.
LOOKS LIKE ANY LIGHT PRECIP WILL TAPER OFF BY SUN...BUT MODELS
CONTINUE TO SHOW THE SUBTROPICAL JET BECOMING ACTIVE EARLY NEXT
WEEK WITH A POTENT S/WV AFFECTING THE REGION POSSIBLY AS EARLY AS
MONDAY. 12Z GFS SHOWS THE AREA REMAINING IN THE COLD SECTOR DUE TO
YET MORE REINFORCING COOL HIGH PRESSURE...BUT PREVIOUS RUNS (AND
ECMWF) HAVE SHOW S TX BACK INTO THE WARM SECTOR. THIS WILL BE KEY IN
DETERMINING THE CHARACTER OF THIS POTENTIAL RAIN/TSTM EVENT EARLY
NEXT WEEK...BUT WE HAVE ALL WEEK TO WATCH MODELS WAIVER AROUND ABOUT
THOSE DETAILS. FOR NOW WILL INTRODUCE POPS ON MON STICKING CLOSE TO
THE 12Z GFS POPS AD TEMPS...AND WILL CONTINUE TO SHOW THE BEST CHC
OF RAIN BEING MON NIGHT AND TUE. GFS AND ECMWF BOTH SUGGEST THIS IS
JUST THE BEGINNING OF AN ACTIVE WEATHER PATTERN NEXT WEEK WITH
SEVERAL OPPORTUNITIES FOR SIGNIFICANT RAIN EVENTS. SO...ENJOY THE
WEATHER WHILE YOU CAN THE NEXT FEW DAYS.
&&
.PRELIMINARY POINT TEMPS/POPS...
CORPUS CHRISTI 64 76 54 68 36 / 10 10 40 10 0
VICTORIA 61 75 49 64 36 / 20 30 60 10 0
LAREDO 61 81 51 73 43 / 10 10 10 0 0
ALICE 61 81 50 70 36 / 10 10 30 10 0
ROCKPORT 64 72 55 68 37 / 20 20 50 10 0
COTULLA 57 77 45 68 37 / 10 10 20 0 0
KINGSVILLE 62 80 54 70 34 / 10 10 30 10 0
NAVY CORPUS 66 75 56 68 41 / 10 20 50 10 0
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 6 AM CST THURSDAY FOR THE FOLLOWING
ZONES: WATERS FROM BAFFIN BAY TO PORT ARANSAS FROM 20 TO 60
NM...WATERS FROM PORT ARANSAS TO MATAGORDA SHIP CHANNEL
FROM 20 TO 60 NM.
&&
$$
JAR/19...SHORT TERM/AVIATION
