740 FXUS64 KSHV 010351 AFDSHV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SHREVEPORT LA 951 PM CST SAT JAN 31 2015 .DISCUSSION... RAINFALL SLOWER TO SPREAD ACROSS THE WESTERN ZONES THIS EVENING SO HAVE ADJUSTED THE TIME OCCURRENCE OF THE EXPECTED CHANCE FOR RAIN. DRY AIR INDICATED OVER MUCH OF THE FORECAST AREA AND WILL TAKE TIME FOR THE MOISTURE TO SATURATE. MADE NOT OTHER CHANGES. /06/ && .PREV DISCUSSION... /ISSUED 557 PM CST SAT JAN 31 2015/ AVIATION... FOR THE 01/00Z TAFS...MVFR CIGS ONGOING ACROSS MUCH OF E TX WILL SPREAD EASTWARD INTO SRN AR/NRN LA. LARGE AREA OF RAIN ACROSS MUCH OF OK/TX WILL ALSO MOVE EWD AND SHOULD BEGIN TO AFFECT KTYR/KLFK BEFORE MIDNIGHT AND THEN THE REMAINDER OF THE TAF SITES BY SUNRISE SUNDAY MORNING. THERE MAY ALSO BE ENOUGH ELEVATED INSTABILITY AHEAD OF AN APPROACHING COLD FRONT AND UPPER TROUGH TO SUPPORT ISOLATED CONVECTION DURING THE DAY SUNDAY SO HAVE CONTINUED TO MENTION THUNDER AREAWIDE. WIND SPEEDS WILL ALSO INCREASE THROUGH THE PERIOD AND SHOULD CONTINUE TO BE GUSTY FROM THE NW AFTER THE FRONT MOVES ACROSS THE AREA SUNDAY AFTERNOON. CIGS/VSBYS SHOULD DETERIORATE AFTER THE RAIN STARTS BUT CONDITIONS WILL LIKELY VARY BETWEEN MVFR/IFR BEYOND MIDNIGHT. /09/ PREV DISCUSSION... /ISSUED 354 PM CST SAT JAN 31 2015/ DISCUSSION... THE LEADING EDGE OF THE STRATOCU RETURN HAS NOW NUDGED NWD INTO THE SW AND WRN SECTIONS OF E TX AS OF MID-AFTERNOON...WITH THE MOISTURE ADVECTION EXPECTED TO INCREASE RAPIDLY THIS EVENING ON A 45-50KT SWRLY LLJ THAT WILL DEVELOP OVER THE SRN PLAINS. THIS WILL BE IN RESPONSE TO HEIGHT FALL AHEAD OF A DEEPENING UPPER TROUGH NOW NOSING INTO CNTRL WY PER THE WATER VAPOR LOOP...THAT WILL AMPLIFY AS IT CROSSES THE CNTRL PLAINS TONIGHT INTO THE SRN PLAINS/MID MS VALLEY SUNDAY. THE MOSAIC RADAR IMAGERY INDICATES A LARGE N-S RAIN SHIELD ACROSS CNTRL/NE OK INTO CNTRL TX ALONG THE I-35 CORRIDOR...WITH A FEW ISOLATED AREAS OF -RA DEVELOPING JUST NW OF SLR. THE PROGS HAVE SLOWED THE PACE AT WHICH THE -SHRA WILL MOVE INTO E TX/SE OK...BUT SHOULD ENTER THESE AREAS BY MID TO LATE EVENING...THUS HAVE TRIMMED BACK THE START TIME OF POPS FARTHER E ACROSS SCNTRL AR/N LA UNTIL AFTER 06Z...WITH THE -SHRA EXPECTED TO BECOME MORE WIDESPREAD LATE. BOTH THE GFS AND NAM INDICATE STRONG LOW LEVEL CONVERGENCE DEVELOPING LATE AHEAD OF A COLD FRONT THAT WILL EXTEND FROM NE AND SRN OK INTO WCNTRL TX BY 12Z SUNDAY...WITH SLIGHTLY BETTER ELEVATED LAPSE RATES ADVECTING IN BENEATH THE UPPER TROUGH. LOW LEVEL AND DEEP LAYER SHEAR HAVE INCREASED FROM PREVIOUS RUNS AS WELL...THUS HAVE ADDED ISOLATED THUNDER TO THE FORECAST FOR NE TX/SE OK/SW AR WELL AHEAD OF THE FRONT. QPF AMOUNTS STILL LOOK TO RANGE FROM 0.25-0.50 INCHES WITH ISOLATED HIGHER AMOUNTS...COMPARABLY LOWER THAN THE LAST FEW SYSTEMS THAT HAVE RESULTED 1-3 INCHES EACH EARLIER THIS MONTH. NOT EXPECTING TEMPS TO FALL MUCH THIS EVENING FROM THE MID-AFTERNOON READINGS...WITH INCREASING SE WINDS AND LATENT HEAT RELEASE FROM THE FALLING WATER DROPLETS FROM A WARMER ENVIRONMENT ALOFT EXPECTED TO CONTRIBUTE TO TEMPS ACTUALLY WARMING LATE. CONVERGENCE ALONG THE FRONT SHOULD WEAKEN BY LATE MORNING/EARLY AFTERNOON SUNDAY AS THE FRONT ENTERS NE TX/SW AR...WITH A LITTLE BETTER SFC/MLCAPES /AROUND 500 J/KG/ DEVELOPING AHEAD OF THE FRONT ACROSS THE EXPANDING WARM SECTOR. THIS SHOULD ALSO SUPPORT THE MENTION OF ISOLATED THUNDER AS WELL AREAWIDE...WITH THE CONVECTION EXPECTING TO DIMINISH FROM W TO E DURING THE AFTERNOON/WITH THE COLD FROPA. PREFER THE SLIGHTLY SLOWER FROPA MOVEMENT THAT THE NAM IS ADVERTISING AS THIS FRONT SHOULD BE SHALLOW AT FIRST...AND MAY STRUGGLE OVERCOMING THE HIGHER TERRAIN OF THE OUACHITAS OVER SE OK/WRN AR. HOWEVER...TEMPS AND DEWPOINTS SHOULD QUICKLY FALL BEHIND THE FRONT...WITH THE PRESSURE GRADIENT TIGHTENING BY SUNDAY NIGHT SUCH THAT PORTIONS OF E TX/SE OK/ADJACENT SW AR WILL BE NEAR LAKE WIND ADVISORY CRITERIA BEFORE THE GRADIENT RELAXES BY DAYBREAK MONDAY. CANADIAN SFC RIDGING WILL SETTLE IN ACROSS THE MID MS VALLEY/SRN PLAINS MONDAY...RESULTING IN MUCH BELOW NORMAL TEMPS AREAWIDE AS THEY STRUGGLE TO REACH THE MID/UPPER 40S. SHOULD SEE A FREEZE AREAWIDE MONDAY NIGHT BEFORE A RETURN SRLY FLOW RESULTS IN TEMPS MODERATING BACK TO NEAR SEASONAL NORMS TUESDAY. THE CLOSED LOW WHICH WILL SHUNT THE BULK OF THE PACIFIC MOISTURE E ACROSS THE REGION OVER THE NEXT 24 HOURS...CONTINUES TO DROPS S INTO NRN BAJA/NW MX THIS AFTERNOON...AND WILL BE A PLAYER IN OUR WEATHER BY MIDWEEK AS IT CROSSES INTO NCNTRL OLD MX TUESDAY AND INTO S TX WEDNESDAY MORNING. BOTH THE GFS/ECMWF HAVE SHIFTED A LITTLE FARTHER S AND SLOWER WITH THE LOW TRACK THAN 24 HOURS AGO...WITH THE PROGS CONTINUING TO BRING SOME LIGHT QPF INTO E TX/N LA TUESDAY NIGHT/WEDNESDAY. GIVEN THE MODEL CONSENSUS /INCLUDING THE CANADIAN/...HAVE RAISED POPS TO MID AND HIGH CHANCE FOR THE SRN ZONES TUESDAY NIGHT AND WEDNESDAY...WITH ANOTHER SHORTWAVE DEVELOPING IN THE NW FLOW ALOFT EXPECTED TO SHIFT ANOTHER COLD FRONT BACK SE INTO THE REGION THURSDAY. THE GFS IS COLDER WITH THE FROPA GIVEN ITS AMPLIFICATION OF THIS NEXT SHORTWAVE THAN THE ECMWF...AND IS CONSISTENT WITH THE CANADIAN SOLUTION AS WELL...WHICH COULD RESULT IN AT LEAST ISOLATED AREAS OF COLD -RA DEVELOPING AREAWIDE THURSDAY NEAR/BEHIND THE FRONT. TEMPS SHOULD TREND BACK TO NEAR SEASONAL NORMS BY FRIDAY...WITH EVEN MILDER AND DRY CONDITIONS EXPECTED NEAT WEEKEND IN TIME FOR THE MARDI GRAS PARADES SCHEDULED TO RESUME ACROSS THE REGION. PRELIMS TO FOLLOW BELOW... && .PRELIMINARY POINT TEMPS/POPS... SHV 54 63 31 47 28 / 70 90 10 0 0 MLU 49 65 34 45 26 / 70 100 30 0 0 DEQ 48 56 25 43 25 / 100 90 10 0 0 TXK 51 60 28 43 26 / 90 100 10 0 0 ELD 49 61 31 44 24 / 80 100 20 0 0 TYR 55 60 28 46 30 / 90 80 10 0 0 GGG 54 62 29 46 28 / 90 90 10 0 0 LFK 56 68 34 49 28 / 70 80 20 0 0 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...NONE. LA...NONE. OK...NONE. TX...NONE. && $$ 06