Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 171124
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
724 AM EDT FRI APR 17 2015

.SYNOPSIS...
A WEAK TROUGH WILL CROSS THE AREA TODAY. HIGH PRESSURE WILL THEN
MOVE IN. A DRY COLD FRONT WILL SLIP DOWN FROM THE NORTH ON
SATURDAY. A COMPLEX FRONTAL SYSTEM WILL BRING RAIN UP FROM THE
SOUTHWEST LATE SUNDAY INTO TUESDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
6 AM UPDATE...
LATEST TRENDS ARE MATCHING WITH EARLIER IDEAS OF A MAINLY DRY DAY
FOR THE NW. IT ALSO SEEMS LIKE MOST MODELS ARE POINTING TO
DIMISHING SHOWERS THIS MORNING BEFORE A REVIVAL THIS AFTERNOON -
MAINLY TO THE S/E OF A JST-UNV-IPT LINE.

PREV...
WIDESPREAD SHOWERS ARE SLIDING STEADILY ACROSS CENTRAL PA AT 06Z.
A WEAK SURFACE TROUGH HAS STARTED TO FORM OVER LAKE HURON AND
EXTENDS INTO WRN OH. WHILE IT IS NOT MUCH OF A FOCUSING
MECHANISM...IT SHOULD PUSH THROUGH THE STATE BY THE END OF THE
AFTERNOON. IT WILL STAY CLOUDY FOR MOST OF THE DAY. THE SHOWERS
WILL HIT ALMOST EVEYONE TODAY...BUT THE COVERAGE SHOULD BE
SCATTERED. SHOWERS SHOULD BE ON THE DECREASE FROM W-E THROUGH THE
DAY. EVEN WITHOUT MUCH CLEARING...THE LI/S DROP WELL BELOW ZERO IN
THE SERN THIRD OF THE AREA IN THE LATE AFTERNOON.
THUS...THUNDERSTORMS ARE EXPECTED JUST AS THE TROUGH EXITS THE
AREA. WILL KEEP MENTIONS OF THUNDER TO THE SERN QUARTER/THIRD.
TEMPS TODAY WILL STRUGGLE INTO THE 60S...SOME L70S ARE POSSIBLE
IN THE SE WHERE THE SUN POKES THROUGH.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
ANY SHRA/TSRA IN THE FAR SE AROUND SUNSET WILL MOVE QUICKLY EAST
AS THEY WEAKEN. THERE SHOULD BE GOOD CLEARING OVERNIGHT...BUT IT
MAY COME SLOWLY AT FIRST. THE RESIDUAL MOISTURE AND A DIMINISHING
WIND DUE TO A HIGH PRESSURE AREA NOSING IN FROM THE OHIO VALLEY
MAY BODE WELL FOR PATCHY FOG. HOWEVER...SUBSIDENCE WILL BE DRYING
OUT THE AIR AS WELL. MINS WILL HOLD IN THE 40S AND L50S. SATURDAY
SHOULD BE FAIR WITH A GENERALLY LIGHT WIND. HOWEVER...A VERY
POTENT SHORT WAVE WILL ZIP THROUGH NEW ENGLAND AND DRAG A DRY
BACKDOOR FRONT THROUGH IN THE MIDDLE OF THE DAY. THIS COULD KICK
THE WINDS UP...ESPECIALLY OVER THE NE. MAXES WILL BE INTO THE 70S
FOR MOST...BUT PERHAPS ONLY THE M-U60S IN THE HIGHER
ELEVATIONS/NW. UPPER RIDGE STAYS JUST TO THE WEST SAT NIGHT...AND
SHOULD KEEP IT MAINLY CLEAR. TEMPS MAY GET FROSTY IN THE NRN
MTNS...WITH 40S ELSEWHERE. THE LIGHT N/E WIND MAY BE ENOUGH TO
KEEP TEMPS FROM REALLY FALLING OFF. SUNDAY LOOKS MAINLY DRY AT
THIS POINT...WITH MOST GUIDANCE NOT BRINING ANY RAIN INTO THE AREA
UNTIL AFTER 21Z. WILL KEEP CHC POPS IN THE SW FOR LATE IN THE
DAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
GOOD TO ABOVE AVERAGE CONFIDENCE NOW IN EXTENDED RANGE FORECAST
WITH LATEST 16/12Z MODELS CONTINUING THEIR TREND OF MUCH BETTER
AGREEMENT ON EVOLUTION OF OVERALL PATTERN AND TIMING. THE KEY
ELEMENTS OF THE FCST ARE NOW BECOMING RATHER CLEAR: 1) THE WEEKEND
SHOULD TURN OUT TO BE DRY! 2) A POTENTIALLY SIGNIFICANT RAINFALL
EVENT IS BEING SIGNALED BY THE MODEL AND ENSEMBLE DATA FOR LATE
SUNDAY NIGHT INTO MONDAY AND 3) BEYOND MONDAY THE PATTERN LOOKS
BLOCKY WITH A CORE OF NEGATIVE HEIGHT ANOMALIES CENTERED OVER THE
MIDWEST/GREAT LAKES/NORTHEAST.

THE UPPER LOW EXITING THE FOUR CORNERS REGION INTO THE CENTRAL
PLAINS WILL MERGE WITH NORTHERN STREAM ENERGY DROPPING SWD ACROSS
SOUTHERN CANADA...EVENTUALLY CARVING OUT A BROAD LW TROUGH OVER
THE EASTERN U.S. AT THE SFC...A DEEPENING LOW WILL TRACK NEWD
THROUGH THE GREAT LAKES WITH ABOVE NORMAL PWS BEING DRAWN NWD
ALONG AND AHEAD OF ITS TRAILING COLD FRONT VIA STRONG SLY FLOW.
AIDED BY THE MAGNITUDE OF THE MSLP...850MB WINDS AND PW
ANOMALIES THE PATTERN RECOGNITION SUGGESTS THE POTENTIAL FOR A
SYNOPTIC TYPE HEAVY RAINFALL EVENT LATE SUNDAY NIGHT INTO MONDAY.
AS THE PARENT UPPER TROUGH TAKES ON A SLIGHT NEGATIVE TILT...IT
ALSO APPEARS THAT A TRIPLE POINT LOW WILL FORM ALONG THE FRONT
OVER THE SRN MID ATLC STATES...WHICH USUALLY SLOWS THE PROGRESSION
AND ENHANCES RAINFALL. CURRENT FORECAST GRIDS ARE IN VERY GOOD
SHAPE...AND MAINTAINED THE TREND OF INCREASED POPS FOCUSED AROUND
DAY 3.5-4/SUNDAY NIGHT-MONDAY WITH ADDED CHC FOR +RA FROM THE
SOUTH CENTRAL MTNS INTO THE SUSQ VLY. BASED ON CAPE
FORECASTS...ADDED A MENTION OF CHANCE TSTM TO THE WEST MONDAY AS
WELL WITH MOISTURE STREAMING IN ON NOTABLE 850MB SOUTHERLY JET.

TEMPS SHOULD TREND COOLER INTO MIDDLE/LATE WEEK WITH SHOWERY /YET
LIGHT/ REGIME ASSOCIATED WITH BROAD CYCLONIC FLOW ALOFT WITH
CLOSED UPPER LOW CENTERED INVOF THE UPPER GREAT LAKES. DETAILS ON
PRECIP DO REMAIN SKETCHY FOR THIS PERIOD...WITH LACK OF GOOD
CONSENSUS IN GUIDANCE AFTER WED WITH DIVERGING SOLUTIONS IN
POSITION OF BROAD TROUGH OVER S CANADA/NORTHEAST U.S.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
A WEAK TROUGH OF LOW PRESSURE WILL PUSH ACROSS CENTRAL PA THIS
MORNING...BRINGING LINGERING SHOWERS TO THE REGION. NR TERM MDL
SOUNDINGS INDICATE LOW LVL MOISTURE ASCENDING THE ALLEGHENY MTNS
WILL CONTINUE TO PRODUCE IFR CIGS AT KBFD THRU ARND 18Z. AS FLOW
VEERS TO THE WEST...UPSLOPING FLOW MAY ALSO RESULT IN A PERIOD OF
IFR CIGS AT KJST BTWN 14Z-18Z. FURTHER EAST...DOWNSLOPING FLOW
WILL LIKELY YIELD NO WORSE THAN MVFR CIGS.

GENERALLY IMPROVING CONDS EXPECTED THIS AFTN...AS WESTERLY FLOW
DRAWS DRIER AIR INTO THE REGION. HOWEVER...CAN/T RULE OUT A BRIEF
SHRA/TSRA AT KMDT/KLNS BTWN 19Z-00Z ASSOC WITH PASSAGE OF UPPER
LVL DISTURBANCE. A RIDGE OF HIGH PRES WILL BUILD INTO THE AREA
TONIGHT...BRINGING WIDESPREAD VFR CONDS AND LGT WIND THIS EVENING.
CAN/T RULE OUT PATCHY RADIATION FOG LATE AT NIGHT/EARLY SAT AM.

OUTLOOK...

SAT-SUN...NO SIG WX EXPECTED.

MON...SHOWERS/LOW CIGS EXPECTED.

TUE...NO SIG WX EXPECTED.

&&

.FIRE WEATHER...
WETTING RAINFALL HAS DECREASED THE WILD FIRE SPREAD THREAT FOR
NOW. HOWEVER...DEWPOINTS WILL BE VERY LOW ON SATURDAY. A WEAK BACK
DOOR FRONT WILL LIKELY KICK UP THE WIND A BIT OVER THE
NORTHEASTERN COUNTIES LATER ON SATURDAY. IF FUELS DO DRY OUT
BY SAT AFTERNOON...THE CONDITIONS MAY BE WORTHY OF A RED FLAG
WARNING. FURTHER GUIDANCE FROM DISTRICT FIRE MANAGERS WILL HELP IN
DETERMINING WHETHER A RED FLAG WARNING MAY BE NECESSARY.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$
SYNOPSIS...DANGELO
NEAR TERM...DANGELO
SHORT TERM...DANGELO
LONG TERM...RXR
AVIATION...FITZGERALD
FIRE WEATHER...



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