Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 210730 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 330 AM EDT MON APR 21 2014 .SHORT TERM...
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(TODAY THROUGH TUESDAY) ISSUED AT 330 AM EDT MON APR 21 2014 06Z SFC ANALYSIS SHOWS A WEAK AREA OF HIGH PRESSURE HOLDING ON OVER EAST KENTUCKY IN THE FACE OF APPROACHING LOW PRESSURE FROM THE PLAINS. ON SATELLITE...PATCHES OF HIGH...AND MOSTLY THIN...CLOUDS ARE DRIFTING OVER EAST KENTUCKY EARLY THIS MORNING WHILE WINDS REMAIN LIGHT. THIS HAS ALLOWED FOR A GOOD NIGHT OF RADIATIONAL COOLING... ESTABLISHING A MODERATE TO LARGE RIDGE TO VALLEY TEMPERATURE DIFFERENCE ACROSS THE CWA. CURRENTLY...READINGS RANGE FROM THE LOWER 40S IN THE MOST SHELTERED VALLEYS IN THE EAST TO THE UPPER 50S AND LOWER 60S ON THE RIDGES...WHILE MORE OPEN AREAS ARE GENERALLY IN THE LOW TO MID 50S. DEWPOINTS...MEANWHILE...VARY FROM THE UPPER 20S ON THE RIDGES IN THE EAST TO MID 40S IN THE WEST AND THROUGHOUT MUCH OF THE CUMBERLAND VALLEY. THE MODELS CONTINUE TO BE IN PRETTY GOOD AGREEMENT WITH THE TRANSFER OF ENERGY FROM A DAMPENING SOUTHERN PLAINS TROUGH TO A MORE WELL DEFINED ONE DIVING SOUTHEAST FROM SOUTH CENTRAL CANADA LATER TODAY. THE REMNANTS OF THE MORE SOUTHERN REFLECTION WILL MOVE THROUGH THE OHIO VALLEY THIS EVENING...BUT THE MAIN IMPETUS FOR WEATHER IN KENTUCKY WILL BE FROM THE MORE NORTHERN TROUGH...AND ITS HEIGHT FALLS...THAT CUTS THROUGH THE EASTERN OHIO VALLEY BY TUESDAY EVENING. ALTHOUGH THERE REMAINS SOME DISCREPANCIES WITH THE MODELS AS THIS PATTERN ADJUSTMENT OCCURS THEY DO AGREE ON THE BROADER FEATURES AND TIMING. AS SUCH...A GENERAL MODEL BLEND WAS FAVORED FOR THE SHORT TERM PORTION OF THE FORECAST. SENSIBLE WEATHER WILL FEATURE ONE LAST PLEASANT...WARM...AND MOSTLY DRY DAY THROUGH EAST KENTUCKY AS A WEAKENING COLD FRONT SENDS INCREASING AND THICKENING CLOUDS INTO THE AREA BY AFTERNOON. MOISTURE WILL BE INCREASING AHEAD OF THIS BOUNDARY...BUT HUMIDITIES WILL STILL BE ABLE TO BOTTOM OUT IN THE UPPER 20S AND LOWER 30S ACROSS THE AREA AHEAD OF ANY SHOWERS INBOUND FOR THE EVENING. WINDS WILL REMAIN RELATIVELY LIGHT...THOUGH...LIMITING FIRE WEATHER CONCERNS OR OPPORTUNITIES. A FEW SHOWERS WILL BE POSSIBLE IN THE EVENING AS THE FRONT PRESSES IN AND THE FIRST POCKET OF WEAK MID LEVEL ENERGY CROSSES THE AREA. A BETTER CHANCE OF MEASURABLE RAINS OF ANY SIGNIFICANCE ARRIVES TOWARD DAWN AS THE ACTUAL COLD FRONT MOVES INTO EAST KENTUCKY. THIS FRONT MAY BE ABLE TO POP OFF A FEW GARDEN VARIETY THUNDERSTORMS AS IT PASSES OWING MAINLY TO LIS APPROACHING -3 AND CAPES NEAR 1000 J/KG...BUT WE WILL LACK A DECENT WIND FIELD AND STRONGER SFC CONVERGENCE THAT COULD DRIVE BETTER CONVECTIVE DEVELOPMENT. ACCORDINGLY...HAVE LIMITED THE SLIGHT CHANCE OF THUNDER TO RIGHT ALONG THE BOUNDARY INTO THE DAY TUESDAY. THE FRONT AND ITS MAINLY SHOWERS MOVES ON THROUGH EAST KENTUCKY BY EARLY AFTERNOON TUESDAY WITH COOLER TEMPERATURES TO FOLLOW. AROUND A QUARTER OF AN INCH OF RAIN ON AVERAGE IS EXPECTED FROM THIS SYSTEM...SO MANY PLACES WILL LIKELY NOT EVEN SEE A GOOD SOAKING...KEEPING CONDITIONS FAIRLY DRY HEADING INTO THE MIDDLE AND LATTER PARTS OF THE WEEK. USED A DIURNAL FROM OBS SCHEME FOR HOURLY TEMPERATURES INTO THE MORNING GIVEN THE WIDE VARIANCE BETWEEN RIDGES AND VALLEYS CURRENTLY UNDER WAY. AFTER THAT...FAVORED THE CURVE FROM THE NAM12 THROUGH THE SHORT TERM PORTION OF THE FORECAST. DID START OUT WITH THE BIAS CORRECTED CONSSHORT GUIDANCE FOR THE DEWPOINTS AND WIND GRIDS FOR THE FIRST 24 HOURS OF THE FORECAST FOLLOWED BY THE BC/CONSALL THEREAFTER. THE DEWPOINTS WERE ADJUSTED LOWER THROUGH EARLY AFTERNOON PER RECENT BEHAVIOR. AS FOR POPS...ENDED UP MOST SIMILAR TO THE HIGHER MAV NUMBERS THROUGH TUESDAY RATHER THAN THE MORE MEAGER MET GUIDANCE. .LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY) ISSUED AT 310 AM EDT MON APR 21 2014 FORECAST MODELS ARE IN GOOD AGREEMENT THROUGH THE WORK WEEK. TRANSIENT RIDGING WILL BUILD ACROSS OUR REGION THROUGH THURSDAY BEFORE GIVING WAY TO A TROUGH DROPPING INTO THE GREAT LAKES REGION BY FRIDAY. MODELS THEN HANDLE THIS TROUGH DIFFERENTLY HEADING INTO THE WEEKEND AND OUR CONFIDENCE IN THE DETAILS OF THE WEEKEND FORECAST DROPS OFF QUITE A BIT. SENSIBLE WEATHER WILL FEATURE DRY AND MILD CONDITIONS ON WEDNESDAY AND THURSDAY. WE WILL LIKELY CONTINUE TO EXPERIENCE LOW RELATIVE HUMIDITY VALUES EACH AFTERNOON AS WELL. A STRUNG OUT COLD FRONT IS THEN PROGGED TO PASS QUICKLY THROUGH OUR AREA LATE THURSDAY NIGHT INTO FRIDAY MORNING. MODEL GENERATED QPF IS LEAN...AS IS INSTABILITY...AND ONLY EXPECT SCATTERED SHOWERS WITH PERHAPS A THUNDERSTORM OR TWO AS THE FRONT PASSES. AS MENTIONED ABOVE... FORECAST MODELS THEN PAINT DIFFERENT SCENARIOS OVER THE WEEKEND...ESPECIALLY WHEN LOOKING AT TEMPERATURES. FOR INSTANCE... RAW MODEL TEMPS ON THE 21/00Z GFS KEEP US IN THE 50S ON SUNDAY WHILE THE 21/00Z ECMWF IS AROUND 80. A MODEL BLEND SEEMS PRUDENT. THIS BLEND RESULTS IN A DRY FORECAST FOR SATURDAY WITH A RETURN TO A SLIGHT CHANCE OF SHOWERS SATURDAY NIGHT AND SUNDAY.
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&& .AVIATION...(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT) ISSUED AT 135 AM EDT MON APR 21 2014 VFR CONDITIONS WILL CONTINUE OVER EAST KENTUCKY THROUGH THE FORECAST PERIOD AS HIGH PRESSURE BEGINS TO DEPART. INCONSEQUENTIAL PATCHES OF THIN HIGH CLOUDS WILL DRIFT OVERHEAD THROUGH THE REST OF THE NIGHT. MOISTURE WILL THEN BEGIN TO INCREASE BY MONDAY AFTERNOON AHEAD OF AN APPROACHING COLD FRONT. THIS WILL LIKELY LEAD TO A CU DECK DEVELOPING BETWEEN 4 AND 6KT FEET MSL BY MID TO LATE AFTERNOON. CLOUDS WILL CONTINUE TO INCREASE AND THICKEN DURING THE EVENING...WITH SHOWERS A POSSIBILITY BEFORE MIDNIGHT AT MOST PLACES. WINDS WILL BE LIGHT AND VARIABLE THROUGH THE REST OF THE NIGHT BEFORE PICKING UP A BIT FROM THE SOUTHWEST TO WEST BY MID AFTERNOON MONDAY...CONTINUING AT 5 TO 10 KTS FROM THAT DIRECTION INTO THE EVENING. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...GREIF LONG TERM...ABE AVIATION...GREIF

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