FXUS64 KHUN 161054 AFDHUN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HUNTSVILLE AL 454 AM CST FRI JAN 16 2015 .DISCUSSION... WATER VAPOR SATELLITE DATA INDICATES THAT THE MID/UPPER-LEVEL TROUGH WHICH WAS LARGELY RESPONSIBLE FOR YESTERDAYS WINTRY PRECIPITATION CONTINUES TO SHIFT EASTWARD OFF THE SOUTHEAST ATLANTIC COAST...WITH STRONG SUBSIDENCE NOW OVERSPREADING THE REGION. THIS -- ALONG WITH THE ADVECTION OF DRIER AIR INTO THE REGION -- HAS ALLOWED FOR THE EROSION OF LOW STRATUS CLOUDS AND SUBSEQUENT DEVELOPMENT OF AREAS OF FREEZING FOG. SPS HAS ALREADY BEEN TRANSMITTED TO ADDRESS THIS ISSUE... AS WELL AS POTENTIAL FOR PATCHES OF BLACK ICE ON AREA ROADWAYS. ALTHOUGH VISIBILITIES ARE GENERALLY IN THE 1-3 MILE RANGE...LOCALLY DENSE FOG IS CERTAINLY POSSIBLE -- ESPECIALLY IN THE TENNESSEE AND PAINT ROCK VALLEYS. AFTER THE FOG BURNS OFF THIS MORNING...WE WILL BEGIN A LONG- AWAITED PERIOD OF PLEASANT WEATHER WITH ABUNDANT SUNSHINE BOOSTING HIGH TEMPERATURES INTO THE UPPER 40S/LOWER 50S TODAY. A SURFACE RIDGE -- CURRENTLY EXTENDING FROM NORTHWEST GULF COAST INTO THE GREAT LAKES -- WILL SHIFT EASTWARD OVERNIGHT WITH ITS AXIS LIKELY ALIGNED ALONG THE EASTERN SEABOARD BY TOMORROW MORNING. IN ANTICIPATION OF CLEAR SKIES AND CALM WINDS...HAVE ADDED PATCHY FREEZING FOG TO THE FORECAST FOR LOCAL RIVER VALLEYS ONCE AGAIN TONIGHT. EVEN WARMER TEMPERATURES ARE EXPECTED SATURDAY...WITH A SWLY FLOW OF 20-30 KNOTS IN THE 925-850 MB LAYER PROMOTING A WELL-MIXED PBL DURING THE AFTERNOON. ALTHOUGH A FEW HIGH CLOUDS -- ASSOCIATED WITH A WEAKENING DISTURBANCE MOVING ALONG THE CENTRAL GULF COAST -- MAY SPREAD ACROSS THE REGION BY LATE AFTERNOON...HIGHS WILL STILL REACH THE UPPER 50S IN THE EAST AND LOWER 60S IN THE WEST. SHORT TERM NWP GUIDANCE REMAINS CONSISTENT IN FORECASTING A NORTHERN STREAM 500-MB SHORTWAVE TROUGH TO SHIFT ACROSS THE NORTHERN ROCKIES TODAY AND INTO THE WESTERN GREAT LAKES BY TOMORROW EVENING. THIS FEATURE WILL BECOME MORE AMPLIFIED WITH TIME AS IT APPROACHES THE TENNESSEE VALLEY SATURDAY EVENING...AND MOVES ACROSS THE REGION EARLY SUNDAY MORNING. A WEAK COLD FRONT WILL ACCOMPANY PASSAGE OF THE MID- LEVEL TROUGH AXIS...WITH THE FRONT EXPECTED TO CROSS THE FORECAST AREA BETWEEN 09-15Z SUNDAY. IT STILL APPEARS AS IF A NARROW BAND OF SHOWERS WILL FORM ALONG THE FRONT AS IT ENTERS THE REGION... ALTHOUGH LACK OF APPRECIABLE DEEP-LAYER MOISTURE IN THIS AREA WILL LEAD TO A HIGHER COVERAGE WHERE MID-LEVEL FORCING IS STRONGER TO THE NORTH/EAST. HOWEVER...A PRONOUNCED VORT MAX DIGGING INTO THE BASE OF THE LONGWAVE TROUGH MAY ENHANCE LIFT...AND WILL MAINTAIN 20-30 POPS BETWEEN 06-12Z AND FOR ONLY THE FAR NORTHEAST CORNER OF THE CWA BETWEEN 12-18Z. LITTLE CHANGE IN TEMPERATURE IS EXPECTED IN THE WAKE OF THIS COLD FRONT AS LOW-LEVEL FLOW WILL QUICKLY RETURN TO THE SOUTHWEST GIVEN ORIENTATION OF SURFACE RIDGE AXIS ALONG THE GULF COAST. EARLY NEXT WEEK MODELS SUGGEST THAT ANOTHER NORTHERN STREAM WAVE WILL DROP SOUTHEASTWARD ACROSS THE NORTHERN PLAINS AND INTO THE MID- MISSISSIPPI VALLEY BY TUESDAY NIGHT. THIS TROUGH IS EXPECTED TO DAMPEN AS IT SHIFTS EASTWARD OVER THE OHIO VALLEY AND INTO THE CENTRAL APPALACHIANS WEDNESDAY...WITH THE ASSOCIATED SURFACE LOW PUSHING ANOTHER COLD FRONT THROUGH THE REGION TUESDAY NIGHT/WEDNESDAY MORNING. HAVE INCLUDED A SLIGHT CHANCE OF SHOWERS FOR TUESDAY NIGHT AND WEDNESDAY DUE TO UNCERTAINTIES IN TIMING OF FRONTAL PASSAGE...BUT IT APPEARS AS IF THE HIGHEST COVERAGE WILL ONCE AGAIN BE TO THE NORTH. A COOLER/DRIER AIRMASS OF PACIFIC ORIGIN WILL REMAIN ACROSS THE REGION WEDNESDAY NIGHT/THURSDAY...WITH CLOUDS EXPECTED TO INCREASE IN ADVANCE OF A LONGWAVE TROUGH APPROACHING FROM THE CENTRAL PLAINS. LIGHT RAIN ASSOCIATED WITH THIS SYSTEM WILL BEGIN TO IMPACT THE REGION...PERHAPS AS EARLY AS THURSDAY AFTERNOON. 70/DD && .AVIATION... /ISSUED 1135 PM CST THU JAN 15 2015/ FOR 06Z TAFS...FOG FORMATION IS EXPECTED AS CLOUDS CONTINUE TO CLEAR FROM NW TO SE ACROSS N AL/S MIDDLE TN. VIS SHOULD GRADUALLY DROP TO MVFR BY 06Z AT KMSL AND LIKELY TO IFR BETWEEN 10Z-15Z. DROPS IN VIS ARE EXPECTED AT KHSV AS WELL BUT ONLY EXPECTING A DROP TO MVFR AT THIS TIME BTWN 06-15Z. INCLUDED A COUPLE OF TEMPO GROUPS BTWN 06-10Z IN AN ATTEMPT TO CAPTURE SOME OSCILLATIONS IN VIS BTWN CATEGORIES. FURTHER DROPS IN CAT ARE POSSIBLE ALONG WITH THE POSSIBILITY FOR FZFG AT KMSL BTWN 10-12Z BUT DID NOT INCLUDE THAT IN TAF DUE TO UNCERTAINTY OF FORMATION AROUND SITE. SL.77 && .PRELIMINARY POINT TEMPS/POPS... HUNTSVILLE 51 30 59 35 / 0 0 0 30 SHOALS 51 29 61 36 / 0 0 0 30 VINEMONT 52 28 60 36 / 0 0 0 20 FAYETTEVILLE 49 27 58 34 / 0 0 0 30 ALBERTVILLE 50 29 58 35 / 0 0 0 20 FORT PAYNE 51 27 59 33 / 0 0 0 20 && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WEATHER.GOV/HUNTSVILLE.
Posted on: Fri, 16 Jan 2015 10:55:33 +0000
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