Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 200511 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 111 AM EDT SUN JUL 20 2014 .SYNOPSIS...
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WEAK SURFACE FEATURES AND A SLOW-MOVING UPPER LEVEL TROUGH OVER THE EASTERN U.S. WILL ALLOW A CHANCE FOR SHOWERS TODAY AND INTO THE EARLY PART OF THE WEEK.
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&& .NEAR TERM /THROUGH TODAY/...
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AS OF 100 AM EDT SUNDAY... MINOR TWEAKS TO EXISTING GRIDS IN TERMS OF POPS TO REFLECT LATEST RADAR TRENDS BUT AIR MASS REMAINS REMARKABLY UNIFORM. PREVIOUS VALID DISCUSSION.. AS OF 158 PM EDT SATURDAY... A BROAD TROF REMAIN ACROSS THE EAST COAST SUNDAY. THE MAIN HIGH PRESSURE CENTER WILL SLIDE EAST OFF THE NEW ENGLAND COAST AS A WAVE OF LOW PRESSURE SLIDES ACROSS GEORGIA AND SOUTH CAROLINA. A LINGERING WEDGE FOR OUR AREA WILL KEEP THE POTENTIAL FOR SOME SHOWERS AND A FEW DIURNAL THUNDERSTORMS...MAINLY IN THE WEST. WENT WITH HIGH TEMPERATURES CLOSE TO THE COOLER ADJMET WITH VALUES FROM LOWER 70S IN THE MOUNTAINS TO AROUND 80 DEGREES IN THE PIEDMONT.
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&& .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... AS OF 330 PM EDT SATURDAY... UPPER TROUGH OVER THE AREA WILL WEAKEN AS WE TRANSITION INTO THE UPCOMING WEEK. MEANWHILE A MAMMOTH 600DM RIDGE WILL BEGIN BUILDING ACROSS THE WESTERN U.S. AND LARGELY CONTROL THE STEERING CURRENTS OVER THE CONUS FOR THE UPCOMING WEEK. IN SPITE OF THE BUILDING HEIGHTS...A DEFINITE AND PERSISTENT WEAKNESS WILL REMAIN LEFT BEHIND FROM THE BASE OF THE EASTERN U.S. TROUGH ACROSS THE SOUTHEAST CONUS AND EVENTUALLY APPEARS TO EVOLVE INTO A PSEUDO TROPICAL LOW ALONG THE GA/SC COAST. MODELS ARE IN FAIR AGREEMENT THIS FEATURE WILL REMAIN PRIMARILY INLAND...AND WITH THE BUILDING RIDGE...THE MODELS RETROGRADE THIS FEATURE WESTWARD INTO THE LOWER MS VALLEY BY MID WEEK. THE FLOW OVER OUR LITTLE PIECE OF REAL ESTATE...AT LEAST THE FIRST HALF OF THE WEEK LOOKS PRETTY DEAD ALOFT...LACKING ANY SIGNIFICANT ADVECTION OF AIR EITHER NORTH OR SOUTH. AS SUCH...EXPECT THE OVERALL AIRMASS TO MODIFY WITH TIME...THE JULY SUN DOING ITS THING TO WARM US UP A FEW DEGREES EACH DAY...TEMPERATURES CLIMBING BACK TO THE SEASONAL NORM. THE SHOWER THREAT WILL BECOME DIURNALLY DRIVEN WITH WIDELY SCATTERED SHOWERS/STORMS DURING THE PEAK HEATING OF THE AFTERNOON AND EVENING ONLY...AND LITTLE OR NO PRECIP THREAT AT NIGHT. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 445 PM EDT SATURDAY... UPPER RIDGE IS FORECAST TO REMAIN OVER THE WESTERN CONUS THROUGH THE LONG TERM...WITH A PERSISTENT UPPER TROUGH OVER THE EASTERN CONUS. A STRONG SHORT WAVE TRACKS FROM SOUTH CENTRAL CANADA ATOP THE UPPER RIDGE TOWARD THE GREAT LAKES. THIS DRIVES A FRONTAL SYSTEM INTO THE EASTERN U.S. AND OUR REGION BY THURSDAY. THE 12Z GFS IS THE MOST AGGRESSIVE WITH THE FRONT COMPARED TO THE LESS AMPLIFIED ECMWF...IN PUSHING THIS FRONTAL SYSTEM THROUGH THE REGION THURSDAY...THEN S-SE OF THE AREA FRI. FOLLOWING THE GFS...THE GREATEST CHANCE FOR SHOWERS/STORMS WILL BE THURSDAY... FOLLOWED BY A DRY FRIDAY AND SATURDAY. THIS SCENARIO WILL ALSO YIELD WEDNESDAY BEING THE WARMEST DAY OF THE WEEK IN ADVANCE OF THE FRONTAL SYSTEM...850MB TEMPS APPROACHING +20C ACROSS MUCH OF THE REGION...WITH LOW 90S IN THE PIEDMONT AND 80S ELSEWHERE. THURSDAY WILL BE A TRANSITION DAY WITH THE FRONTAL PASSAGE...FOLLOWED BY 4 TO 7 DEGREE DOWNTICK IN TEMPERATURES FOR FRIDAY AND SATURDAY. IF THERE IS ANY CHANCE OF ORGANIZED STORMS THIS WEEK IT WOULD MOST LIKELY OCCUR WITH THE FRONTAL PASSAGE THURSDAY. ANYTHING BETWEEN NOW AND THEN WILL BE DIURNALLY DRIVEN WITH AND FOCUSED MAINLY OVER THE MTNS...WEAK FORCING NOT PROVIDING FOR MUCH SUPPORT FOR ANYTHING ORGANIZED. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... AS OF 735 PM EDT SATURDAY... PATCHY LIGHT RAIN SHOWERS WERE PROGRESSING THROUGH THE AREA CURRENTLY GENERALLY ALONG AND EAST OF A KLWB-KDAN LINE. MOST AREAS WERE VFR WITH PATCHY MVFR CONDITIONS FOR MAINLY VSBYS REPORTED. THROUGH THE OVERNIGHT HOURS...WE EXPECT A GENERAL TREND TOWARD MVFR CONDITIONS ACROSS MUCH OF THE AREA AS MVFR LIGHT FOG BECOMES MORE PREVELENT...AND CEILINGS DEVELOP AROUND THE INVERSION LEVEL. A FEW SPOTS MAY EXPERINCE IFR CONDITIONS FOR BOTH CIGS AND VSBYS FOR A FEW HOURS TOWARD DAYBRAK SUNDAY. SUB-VFR CONDITIONS ARE EXPECTED TO IMPROVE TO VFR BY 14-15Z/10-11AM ON SUNDAY. ANOTHER WAVE OF ENERGY IS EXPECTED TO PROGRESS INTO THE REGION BETWEEN 18-00Z/2PM-8PM ON SUNDAY. LOOK FOR ANOTHER INCREASE IN SCATTERED RAIN SHOWERS...ESPECIALLY ACROSS THE MOUNTAINS...AND SOME ISOLATED THUNDERSTORMS CANNOT BE RULED OUT. AS OF 125 PM EDT SATURDAY... EXTENDED AVIATION DISCUSSION... PRECIPITATION WILL BECOME MORE SCATTERED AND DIURNAL IN NATURE SUNDAY AFTERNOON THROUGH WEDNESDAY...WITH A BETTER POTENTIAL FOR AFTERNOON/EVENING THUNDERSTORMS...AS WELL WITH WARMER TEMPERATURES AND MORE UNSTABLE CONDITIONS. THIS WILL RESULT IN BRIEF PERIODS OF MVFR-IFR CIGS IN SHRA/TSRA AS WELL AS INCREASING POTENTIAL FOR LATE NIGHT/EARLY MORNING FOG AND LOCALIZED IFR-LIFR VSBYS WHERE RAIN OCCURS THE PREVIOUS AFTERNOON. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...KK NEAR TERM...CF/PC SHORT TERM...PM LONG TERM...PM/RAB AVIATION...DS/KK

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