FXUS62 KRAH 041022 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 345 AM EDT SAT JUL 4 2009 .SYNOPSIS... WEAK HIGH PRESSURE WILL LINGER OVER THE CAROLINAS TODAY. A LOW PRESSURE SYSTEM WILL APPROACH FROM THE WEST TONIGHT AND CROSS THE REGION SUNDAY AND SUNDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 245 AM SATURDAY... TODAY: ANOTHER DRY/CAPPED AND ATYPICALLY COMFORTABLE JULY DAY WITH DEWPOINTS AGAIN IN THE 50S EXPECTED. SKIES WILL START THE DAY MOSTLY SUNNY (A LITTLE CIRRUS)... THOUGH INCREASING MID AND HIGH CLOUDINESS IN WNW FLOW ALOFT MAY FILTER THE SUNSHINE A BIT BY LATE AFTERNOON. PROJECTED LOW LEVEL THICKNESSES AROUND 1410 +/- 5 METERS SUGGEST HIGH TEMPERATURES 3-5 DEGREES WARMER THAN THOSE OF FRIDAY... RANGING FROM 86 DEGREES OR SO AT INT TO LOWER 90S AT MEB AND FAY. TONIGHT: A DEVELOPING WARM FRONTAL ZONE TO OUR WEST AND SOUTHWEST... AHEAD OF A STORM SYSTEM OVER THE CENTRAL PLAINS THIS MORNING... WILL APPROACH THE REGION OVERNIGHT. WHILE CLOUDS SHOULD CONTINUE TO THICKEN AND LOWER IN RESPONSE TO A STRENGTHENING MID LEVEL WAA REGIME (PARTICULARLY ACROSS THE NORTHERN PIEDMONT)... ANY PRECIPITATION SHOULD HOLD OFF UNTIL CLOSE TO OR AFTER DAYBREAK OWING TO A CONTINUED DRY LOW LEVEL AIRMASS. EVEN THEN... WILL MENTION A SLIGHT CHANCE OF A SHOWER ONLY IN THE NORTHERN AND WESTERN PIEDMONT... IN CLOSER PROXIMITY TO THE PRECIPITATION SHIELD EXPECTED TO SPREAD FROM THE UPPER MIDWEST THIS MORNING INTO THE VIRGINIAS OVERNIGHT. THE INCREASING CLOUD COVER AND RESULTANT L/W RADIATION SUGGEST OVERNIGHT LOWS A COUPLE OF DEGREES ABOVE CONSENSUS MOS... GENERALLY UPPER 60S TO AROUND 70 DEGREES. -MWS && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 345 AM SATURDAY... FOR SUNDAY AND SUNDAY NIGHT: AN H85 WARM FRONT AND ASSOCIATED STRONG LLJ (ON THE ORDER OF 25-40 KTS AT H85)... AND RESULTANT STRONG LOW LEVEL WARM MOIST ADVECTION WILL CONTRIBUTE TO BROAD LARGE SCALE ASCENT ACROSS CENTRAL NC THROUGH SUNDAY EVENING. THE ASCENT SHOULD BE AUGMENTED BY THE DIVERGENT RIGHT ENTRANCE REGION OF A 80-100 KT UPPER LEVEL JET. THESE FORCING FEATURES... IN CONJUNCTION WITH AN INCREASE IN PRECIPITABLE WATER VALUES TO BETWEEN 1.75 AND 2.25 INCHES... SUGGEST SHOWERS AND PERHAPS THUNDERSTORMS WILL BE LIKELY. THE NWP MODELS INDICATE THE PRIMARY SURFACE FRONTAL ZONE MAY BE SUPPRESSED OVER EXTREME SOUTHERN NC OWING TO WIDESPREAD CLOUD COVER WITHIN THE PRIMARY LOW-MID LEVEL FRONTAL CLOUD BAND OVER VA AND MOST OF NC. THE WIDESPREAD CLOUD COVER SHOULD SERVE TO MAINTAIN RELATIVELY WEAK LOW TO MID LEVEL LAPSE RATES THAT MAY LIMIT THE COVERAGE AND STRENGTH OF ANY THUNDERSTORMS. HOWEVER... THE NWP MODELS DO INDICATE THAT SOME DEGREE OF MID LEVEL DRYING MAY TAKE PLACE ABOVE THE INCREASINGLY MOIST AND SATURATED H85 LLJ... WHICH MAY CONTRIBUTE TO POTENTIAL/CONVECTIVE INSTABILITY AND RESULTANT CAPE THAT THE MODELS CURRENTLY FAIL TO DEPICT. A CONDITIONAL SEVERE WEATHER THREAT EXISTS IF ANY SUSTAINED UPDRAFTS INDEED FORM... GIVEN THE STRENGTH AND VEERING OF THE LOW TO MID LEVEL WIND FIELDS WITHIN THE STRONG LOW-MID LEVEL WAA REGIME. DMGG WINDS AND TORNADOES WOULD BE A THREAT FOR ANY STORMS THAT CAN ROOT INTO THE BL. GIVEN THE EXPECTED CLOUD COVER AND PRECIPITATION... HAVE LOWERED TEMPERATURES TO REFLECT HIGHS IN THE 76 TO 85 DEGREE RANGE FROM NW TO SE... AND THESE MAY STILL BE OPTIMISTIC BY A CATEGORY OR EVEN TWO... ESPECIALLY OVER CENTRAL AND NORTHERN ZONES. THE PASSAGE OF A TRAILING H85 COLD FRONT AND SOUTHWARD SETTLING JET ALOFT SUGGEST PRECIPITATION SHOULD DIMINISH FROM NW TO SE SUNDAY NIGHT. WILL ACCORDINGLY TAPER POPS INTO THE CHANCE RANGE... HIGHEST SE... BY MONDAY MORNING. OVERNIGHT LOWS IN THE MIDDLE 60S TO LOWER 70S. WHILE THE NWP MODELS CONTINUE TO WAFFLE REGARDING QPF... PARTICULARLY THE CONVECTIVE FEEDBACK AFFLICTED GFS... THE RELATIVELY STEADFAST AND FAVORED ECMWF INDICATES STORM TOTAL PRECIPITATION AMOUNTS COULD RANGE FROM ONE TO AS MUCH AS TWO INCHES ACROSS PORTIONS OF CENTRAL NC. MONDAY AND MONDAY NIGHT: THE UPPER JET AND LOW LEVEL FRONTAL ZONE ARE EXPECTED TO STALL AND LURK JUST TO OUR SOUTH THIS PERIOD... WHICH MAY SLOW THE CLEARING AND DRYING TREND OVER SOUTHERN NC. WILL ACCORDINGLY MAINTAIN MORE CLOUD COVER AND A LOW CHANCE OF SHOWERS AND ISOLATED THUNDERSTORMS OVER THE EXTREME SOUTHERN PORTIONS OF THE FORECAST AREA THROUGH MONDAY EVENING... WITH A DRIER NORTHERLY FLOW EXPECTED TO OTHERWISE ENVELOPE THE FORECAST AREA... AS WEAK HIGH PRESSURE NOSES INTO THE REGION FROM THE NW. -MWS && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 300 AM SATURDAY... DRY AIR WILL AGAIN BE IN PLACE OVER CENTRAL NORTH CAROLINA TUESDAY UNDER WEST TO WEST NORTHWEST FLOW ALOFT. BROAD MID LEVEL RIDGING OVER THE MIDWEST CROSSES THE MISSISSIPPI RIVER WEDNESDAY NIGHT ALLOWING DRY CONDITIONS TO PERSIST. NO MORE THAN ISOLATED AFTERNOON THUNDERSTORMS POSSIBLE GIVEN THE DRYNESS AND LACK OF A SIGNIFICANT TRIGGER OTHER THAN AFTERNOON HEATING. ANY MIDWEST MCS ACTIVITY IS LIKELY TO BE STEERED NORTH OF OUR AREA UNTIL AT LEAST FRIDAY. RAIN CHANCES FOR THE EXTENDED PERIOD ARE TOO LOW TO MENTION IN THE TEXT PRODUCTS. LOW LEVEL THICKNESS NEAR TO BELOW SEASONAL NORMALS INTO THURSDAY. AFTERNOON HIGH TEMPERATURES 85 TO 92 EXCEPT 90 TO 95 POSSIBLE FRIDAY. OVERNIGHT LOWS OF 65 TO 70. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... AS OF 200 AM SATURDAY... VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. A FEW CUMULUS PERSIST TONIGHT AND HEATING OF THE DAY WILL PRODUCE CLOUDS NEAR 7000 FEET BY LATE MORNING. MOISTURE IN THE AIR COLUMN WILL BE ON THE INCREASE TODAY AND EXPECT BROKEN CLOUDS NEAR 7000 AS SUNSET APPROACHES... AND PERSISTING INTO THE NIGHT. LIGHT WINDS BECOMING WEST SOUTHWEST LESS THAN 10 MPH DURING THE AFTERNOON. MOISTURE WILL CONTINUE TO INCREASE LATE SATURDAY NIGHT INTO SUNDAY AS A FRONT APPROACHES THE AREA. SHOWERS AND THUNDERSTORMS ACROSS CENTRAL NORTH CAROLINA SUNDAY AFTERNOON INTO SUNDAY NIGHT. VFR CONDITIONS ARE EXPECTED MONDAY THROUGH WEDNESDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...HARTFIELD LONG TERM...99 AVIATION...99