FXUS64 KHUN 240758 AFDHUN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HUNTSVILLE AL 258 AM CDT TUE JUN 24 2014 .SYNOPSIS... THE FORECAST FOR THE NEXT 7 DAYS CENTERS OVER THE PROGRESSION OF A WEAKLY AMPLIFIED SHORTWAVE MOVING ACROSS THE SOUTHEAST ATOP A TROPICAL AIRMASS AND THE TRANSITION TO AN AMPLIFIED UPPER PATTERN BY THE END OF THE FORECAST. CURRENTLY, THE PRIMARY FEATURES WITHIN THE UPPER FLOW PATTERN INCLUDE AN UPPER LOW OVER THE GULF OF ALASKA, WEAK RIDGING OUT WEST AND EAST WITH THE MID-LEVEL SHORTWAVE, IN BETWEEN THE TWO RIDGES, CROSSING THE MS RIVER VALLEY. A LINE OF SHOWERS AND STORMS AHEAD OF THIS WAVE HAS MOSTLY BECOME A DISORGANIZED CLUSTER OF SHOWERS OVER MS EARLY THIS MORNING. SL.77 && .SHORT TERM (TODAY THROUGH THURSDAY NIGHT)... THE AREA OF SHOWERS AND STORMS OVER MS MAY ARRIVE BY 6-7 AM THIS MORNING OVER NW AL BEFORE DIMINISHING. HI RES MODEL OUTPUT FOR THE MOST PART ADVERTISES ITS DEMISE SHORTLY AFTER ARRIVAL. HOWEVER, WITH THE APPROACH OF THE MID-LEVEL SHORTWAVE TROUGH, DEEP CONVECTIVE RE-DEVELOPMENT IS LIKELY LATE THIS MORNING INTO THE AFTERNOON. THE ANTECEDENT, VERY SATURATED COLUMN WITH PWATS CLOSE TO 2.0 INCHES AND MID-LEVEL LAPSE RATES CLOSE TO 6-7 DEGREES C/KM SHOULD YIELD ENOUGH INSTABILITY FOR VERY HEAVY RAINFALL PRODUCING THUNDERSTORMS. ON THE INSTABILITY FRONT, FROM THE FORECAST SOUNDINGS AND PLAN VIEW REPRESENTATIONS, SBCAPES ARE CLOSE TO 1200 J/KG. FURTHERMORE, FORECAST SOUNDING PROFILES REVEAL THAT THE ENVIRONMENT MAY NOT BE CONDUCIVE TO A WIDESPREAD MICROBURST THREAT, BUT COULD STILL SEE SOME GUSTY WINDS FROM STRONG DOWNDRAFTS. WHAT WILL LIKELY BE THE PRIMARY THREAT IS HEAVY RAINFALL AND LOCALIZED FLASH FLOODING ESPECIALLY OVER AREAS THAT HAVE RECEIVED RAINFALL OVER THE PAST FEW DAYS (I.E. NW AL AND AREAS S OF TN RIVER). THE GOOD NEWS IS THAT LOW-MID LEVEL STEERING FLOW/STORM MOTION SHOULD BE BETWEEN 20-30 KTS WHICH WOULD DIMINISH THE THREAT OF STORMS REMAINING OVER ONE AREA FOR A LONG PERIOD OF TIME. HOWEVER, IT DOES NOT KEEP STORMS FROM TRAINING OVER THE SAME AREA. GIVEN THE UNCERTAINTY WITH STORM TRAINING AND ENOUGH RUNOFF TO CAUSE WIDESPREAD FLASH FLOODING, HAVE HELD OFF ON A FLASH FLOOD WATCH. NEVERTHELESS, ANY FLOOD PRONE LOCATIONS WILL BE SUSCEPTIBLE TO FLOODING IF STORMS TRAIN OVER THE SAME LOCATION. THE TEMPERATURE FORECAST IS A BIT CHALLENGING GIVEN THIS SCENARIO, BUT OVERALL HAVE KEPT DAYTIME HIGH TEMPS LOWER TODAY WITH HIGHS IN THE MID TO UPPER 80S. THUNDERSTORMS SHOULD CONTINUE THROUGH THE EVENING AND PERHAPS OVERNIGHT TONIGHT AS THE MID-LEVEL SHORTWAVE MOVES EASTWARD ACROSS THE TN VALLEY AND APPALACHIANS. AN ANALYSIS OF THE TIMING SHOWS THAT THE BULK OF THE THUNDERSTORM ACTIVITY SHOULD COME TO AN END ON EARLY WEDNESDAY MORNING. OVERNIGHT LOWS WILL BE WARMER THAN THE PAST FEW NIGHTS GIVEN THE HIGHER DEWPOINTS THAT ARE EXPECTED AND NOT MUCH IN THE WAY OF RADIATIVE COOLING TAKING PLACE. THE WARMER TEMPS TONIGHT COULD BE MITIGATED BY A POSSIBLE COLD POOL, BUT WILL KEEP LOW 70S DUE TO UNCERTAINTIES WITH ITS EXTENT. HAVE KEPT POPS LOWER FOR BOTH WEDNESDAY AND THURSDAY, BUT THERE IS STILL A THREAT FOR THUNDERSTORMS AS THE MEAN UPPER FLOW REMAINS ZONAL AND A FEW WEAK UNDULATIONS MOVE ACROSS THE TN VALLEY. IT IS CHALLENGING TO ASCERTAIN THE STRENGTH OF THESE WAVES, BUT IT DOES APPEAR THAT THERE WILL BE ENOUGH LIFT TO SUPPORT AT LEAST SCATTERED THUNDERSTORMS DURING PEAK DAYTIME HEATING ON BOTH DAYS. .LONG TERM (FRIDAY THROUGH MONDAY)... A PATTERN CHANGE THAT HAS BEEN DEPICTED WITHIN THE MED RANGE MODEL OUTPUT OF THE ECMWF LOOKS MORE AND MORE PROBABLE AS THE GULF OF ALASKA LOW MOVES AND DEEPENS OVER THE WESTERN TIER OF THE U.S. AS IT DOES SO, A RIDGE OVER THE CARIBBEAN AND GULF OF MEXICO LOOKS TO BEGIN BUILDING NORTH TOWARDS THE SOUTHEAST ON FRIDAY INTO SATURDAY. AS IT DOES SO, THE SOUTHEAST WILL SHIFT BACK INTO MORE OF A SUMMERTIME AFTERNOON/EVENING THUNDERSTORM REGIME. AS SUCH, HAVE KEPT LOWER POPS THIS WEEKEND WITH TEMPERATURES CLOSER TO CLIMATOLOGICAL NORMALS OR SLIGHTLY ABOVE NORMAL. BY SUNDAY INTO MONDAY, THE RIDGE WILL BUILD AND BECOME STACKED OVER THE SOUTHEAST. THOUGH IT DOES NOT NECESSARILY MEAN THE COMPLETE DEATH OF ALL CONVECTIVE ACTIVITY THOSE DAYS, DID KEEP A 20 PERCENT CHANCE FOR THUNDERSTORMS FOR NOW AS THE DEPTH OF THE RIDGE IS STILL UNCERTAIN. IT WILL AT LEAST MEAN VERY HUMID AND HOT CONDITIONS THOUGH. THUS, HAVE ADJUSTED THE TEMPERATURES HIGHER TO REFLECT THAT TREND. SL.77 && .AVIATION... /ISSUED 1220 AM CDT TUE JUN 24 2014/ FOR 06Z TAFS... COMPLEX OF SHOWERS AND THUNDERSTORMS MOVING THRU NORTHERN AND CENTRAL MS WILL ARRIVE IN NW AL INCLUDING KMSL FROM 10-13Z, AND KHSV FROM 12-15Z. THE PRECIPITATION WILL PRODUCE FLIGHT RESTRICTIONS INTO THE MVFR CATEGORY, AND POSSIBLY LOWER IF +RA RESULTS. AN UPPER LEVEL DISTURBANCE TRACKING THRU THE REGION ON TUESDAY WILL PRODUCE SCT TO NMRS TSRA THRU THE DAY, SO HAVE MAINTAINED VCTS THRU TUESDAY EVENING. AK && .PRELIMINARY POINT TEMPS/POPS... HUNTSVILLE 86 71 90 68 / 90 50 40 30 SHOALS 87 72 91 68 / 90 50 40 30 VINEMONT 86 71 87 67 / 90 50 40 30 FAYETTEVILLE 85 70 89 66 / 90 50 40 30 ALBERTVILLE 85 69 88 67 / 90 50 50 30 FORT PAYNE 85 70 88 67 / 90 50 50 30 && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WEATHER.GOV/HUNTSVILLE.
Posted on: Tue, 24 Jun 2014 07:59:14 +0000
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