Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 070150
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
850 PM CDT MON JUL 6 2015

.UPDATE...
ISSUED AT 849 PM CDT MON JUL 6 2015

SHOWER AND THUNDERSTORM ACTIVITY OVER NORTHEAST ARKANSAS INTO
SOUTHWEST ILLINOIS IS PERSISTING AHEAD OF A MESOSCALE SHORTWAVE
DEPICTED IN THE NAM-WRF MODEL GUIDANCE AHEAD OF THE MAIN
TROUGH/SURFACE FRONT BISECTING MISSOURI FROM SOUTHWEST TO
NORTHEAST INTO NORTHERN ILLINOIS. AGEOSTRPOPHIC RESPONSE IS SEEN
IN THE DIFFERENTIAL WIND SPEEDS AND MOISTURE CONVERGENCE MOVING UP
THE AR/TN/MS/MO DELTA REGION...PROVIDING THE A LOCALIZED MOISTURE
SOURCE FOR THE UPPER WAVE. THIS SHOULD HELP MAINTAIN ISOLATED TO
LOCALLY SCATTERED CONVECTION ACROSS SOUTHERN SECTIONS OF THE WFO
PAH FORECAST AREA. ATTEMPTED TO BLEND WITH PREVIOUS DAYSHIFT
LARGER SCALE POP GUIDANCE.

THE SUBDIVISION OF THE FORECAST PERIOD WILL LIKELY CAUSE SOME
WORDING CHANGE IN THE TEXT PRODUCTS...WITH LESSER IMPACT TO
TABULAR AND GRIDDED FORECASTS.


UPDATE ISSUED AT 603 PM CDT MON JUL 6 2015

UPDATED AVIATION DISCUSSION FOR 00Z TAF ISSUANCE.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 222 PM CDT MON JUL 6 2015

ISOLATED SHOWERS AND STORMS...FORMING ALONG AN EDGE OF
INSTABILITY.. CONTINUE TO POP UP ACROSS PARTS OF SOUTHEAST
MISSOURI AND DIE OFF AS THEY APPROACH THE MISSISSIPPI RIVER.
THESE WILL TAPER OFF INTO THE EVENING.

ISOLATED TO SCATTERED PRECIPITATION WILL BE POSSIBLE OVERNIGHT
AHEAD OF A COLD FRONT THAT WILL APPROACH THE FORECAST AREA ON
TUESDAY. MODELS ARE IN AGREEMENT BRINGING THE FRONT INTO SOUTHEAST
MISSOURI AND SOUTHERN ILLINOIS. THE FRONT WILL STALL FROM
APPROXIMATAELY CAPE GIRARDEAU MO EAST ALONG AND JUST NORTH OF THE
OHIO RIVER. WHILE WE ARE OUTLOOKED IN A MARGINAL RISK...HEAVY RAIN
IS THE MAIN THREAT WITH BRIEF BUT HEAVY DOWNPOURS. THE FRONT WILL
LIFT BACK NORTH ON WEDNESDAY AS A WAVE DEVELOPS ALONG THE FRONT
AND MOVES NORTHEAST. THIS WILL KEEP CHANCE POPS ON WEDNESDAY.

CLOUDS AND PRECIPITATION WILL KEEP HIGH IN THE LOWER TO MIDDLE
80S. SOME GUIDANCE WANTS TO KEEP HIGHS IN THE 70S ON WEDNEDAY.
HAVE TRENDED DOWN BUT NOT THAT FAR. LOWS WILL GENERALLY BE IN THE
LOWER 70S TONIGHT. TUEDAY NIGHT LOWS WILL RANGE FROM THE MIDDLE
60S AROUND MOUNT VERNON IL TO THE LOW 70S AROUND HOPKINSVILLE.

.LONG TERM...(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 222 PM CDT MON JUL 6 2015

IRONICALLY...SOME OF THE PRECIPITATION CHANCES FOR THE BEGINNING OF
THE EXTENDED FORECAST PERIOD MAY DEPEND ON THE EVOLUTION OF THE
MINOR SHORTWAVE CURRENTLY MOVING INTO THE LONGER SHORTWAVE HEADING
ACROSS NORTHERN MINNESOTA.  IF THIS PROVES TO BE SLIGHTLY STRONGER
AND FURTHER SOUTH THAN ORIGINALLY FORECAST, THIS COULD ACCELERATE
THE MOVEMENT OF THE TUESDAY SYSTEM FURTHER SOUTH...ALLOWING FOR THE
BASE OF THE FASTER WEST-SOUTHWEST UPPER FLOW TO PUSH FURTHER SOUTH
ACROSS THE WFO PAH FORECAST AREA ON WEDNESDAY.

THE SCENARIO MENTIONED ABOVE IS MORE IN LINE WITH THE 12Z MONDAY
DETERMINISTIC GFS MODEL SOLUTION AND IS PREFERRED SLIGHTLY OVER THE
12KM NAM-WRF WHICH KEEPS THE BAROCLINIC ZONE AND DEEPER HEIGHT FALLS
FURTHER TO THE NORTHWEST OVER NORTHERN MISSOURI AND ILLINOIS.

AT THIS TIME...LEANED TOWARD THE GFS SOLUTION IN ASSOCIATED WITH THE
BLENDED MODEL SUITE GUIDANCE.

THIS PACKAGE BEGINS WITH THE SLOW RETROGRADING OF THE FRONTAL ZONE
BACK TO THE NORTHWEST...THEN NORTH...AS THE SOUTHEAST U.S. HIGH
PRESSURE RIDGE AXIS MOVES WEST AND NORTHWEST THROUGH THE
FORECAST...IMPINGING ON BOTH THE DIRECT MOISTURE FLOW FROM THE GULF
OF MEXICO AND THERMAL CAPPING ALOFT FROM THE SOUTH.

AS THE BROAD HIGH PRESSURE IN THE LOWER MISSISSIPPI/TENNESSEE
VALLEYS BEGINS TO BUILD NORTHWEST INTO THE WFO PAH FORECAST AREA.
THE FLOW ALOFT BECOME MORE NORTHWEST WITH TIME. BY SUNDAY NIGHT INTO
NEXT MONDAY...THE RIDGE HAS RETROGRADED ENOUGH THAT THE BASE OF
BAROCLINIC ZONE HAS SHIFTED BACK TO THE SOUTHWEST. THIS WILL BRING
THE HIGHEST CHANCES FOR RAIN INTO SOUTHEAST ILLINOIS...SOUTHWEST
INDIANA AND THE PENNYRILE REGION OF WEST KENTUCKY EARLY NEXT WEEK.

GIVEN A POSITIVE BIAS OF 1 DEGREE ON MAX/MIN TEMPERATURES...ADJUSTED
DAILY MAX/MINS DOWN ONE DEGREE DURING THE EXTENDED PERIOD.

SOMEWHAT LOW CONFIDENCE ON QPF (RAINFALL AMOUNTS) AT THIS TIME.
GIVEN THE PROXIMITY OF THE SURFACE FRONTAL BOUNDARIES TO THE
NORTHERN PART OF THE WFO PAH FORECAST AREA...THERE MAY BE QUITE A
GRADIENT OF RAINFALL...ESPECIALLY IF THERE IS ORGANIZED MCS`S THAT
DEVELOP AND MATURE ALONG THE BOUNDARY. THE TIMING AND PROXIMITY OF
THE MCS`S WILL DETERMINE THE DEGREE AND INTENSITY OF THE
PRECIPITATION SHIELD.

THE LAST COUPLE OF DAYS OF THE GFS/ECMWF CONTINUE TO SHOW A GREATER
INFLUENCE OF THE RIDGE BUILDING LATER ON FRIDAY AND THROUGH THE
WEEKEND. THIS FORECAST CONTINUES THAT TREND THROUGH SUNDAY.

&&

.AVIATION...
ISSUED AT 603 PM CDT MON JUL 6 2015

DECAYING CONVECTION MAY LEAD TO TEMPO LOW VFR CIGS FOR THE FIRST
00-03 HRS BUT AFTERWARD SHOULD JUST SEE MID-HIGH SCT-BKN CLOUDS.
LATER TONIGHT-EARLY TMRW...ANOTHER SHOT OF SHOWERS/STORMS...INHERITED
AND CONTINUED VIA PROB30S...WILL OFFER NEXT LOWER CIG OR FLIGHT
RESTRICTED VSBYS. THAT`LL SCOUR AND LEAD TO LOWER VFR CLOUDS
TMRW...WHICH WILL PROB EVENTUALLY LEAD TO ANOTHER CHANCE LATER IN
THE DAY OR TOWARD EVENING...BUT LEFT OUT THIS WRITING.


&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
MO...NONE.
IN...NONE.
KY...NONE.
&&

$$

UPDATE...SMITH



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