HAMweather.com Area Forecast Discussion for County Warning Area GYX

Thu, 16 Feb 2012 12:32:24 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
614 AM EST THU FEB 16 2012

.SYNOPSIS...
A WEAK RIDGE OF HIGH PRESSURE SHIFTS OFFSHORE TODAY. LOW PRESSURE
APPROACHES FROM THE LOWER GREAT LAKES TONIGHT...AND WILL PRODUCE
SOME LIGHT RAIN AND SNOW TONIGHT INTO FRIDAY MORNING. THE LOW
WILL TRACK DOWN THE SAINT LAWRENCE VALLEY ON FRIDAY...PULLING 
COLD FRONT ACROSS THE AREA. HIGH PRESSURE WILL BUILD IN FOR
SATURDAY. ON SUNDAY...LOW PRESSURE WILL TRACK OUT OF THE GULF
STATES SAT NIGHT...AND AND LOOKS TO REMAIN WELL SOUTH OF NEW
ENGLAND AS IT MOVES EAST ON SUNDAY. LARGE HIGH PRESSURE SETTLES IN
OVER THE EAST COAST MONDAY AND TUESDAY.

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
610 AM...TOOK THE FLURRIES OUT OF THE FORECAST THIS MORNING...AND
ADJUSTED SKY COVER AND TEMPS A BIT...BUT NOTHING SIGNIFICANT.

PREVIOUSLY...SOME SUN CAN BE EXPECTED THROUGH MIDDAY AS TEMPS
WARM ABV NORMAL ONCE AGAIN....AS SFC HIGH TRAVERSES THE CWA THIS
MORNING AND EARLY AFTERNOON. GIVEN THE LACK OF FLOW...AND SOME
DAYTIME HEATING...EXPECT AN ONSHORE FLOW TO DEVELOP THIS
AFTERNOON...KEEPING THE COAST A BIT COLDER THAN THE LAST COUPLE
DAYS. MID TO HIGH CLOUDS MOVE IN FROM THE W IN ADVANCE OF NEXT
SYSTEM...BUT ANY PRECIP SHOULD HOLD OFF UNTIL AROUND OR AFTER
SUNSET IN ALL BUT FAR SW ZONES.

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
BEST DYNAMICS FOR THIS APPROACHING SYSTEM WILL BE ASSOCIATED WITH
CLOSING 500MB AND DEVELOPING SFC LOW TRACKING ALONG...BUT N OF ST
LAWRENCE VLY. HOWEVER WILL SEE OCCLUSION MOVE ACROSS NRN ZONES THU
NIGHT...WITH SOME WEAK WA PRODUCING LIGHT PRECIP THU NIGHT...AND
COLD PROVIDING AROUND FRI MORNING. ALL IN ALL PRECIP LOOKS
LIGHT...LESS THAN A QUARTER INCH IN MOST SPOTS. WITH WARM BL IN
PLACE...SHOULD BE A RA OR SN EVENT WITH MAINLY SN IN THE MTNS THU
NIGHT...AND PERHAPS A BRIEF PERIOD OF SN AT THE START ON THE
COASTAL PLAIN...BEFORE CHANGING TO JUST RAIN. EXPECTING ON THE
ORDER OF 1-2 INCHES IN THE N...WITH AN INCH OR LESS EVERYWHERE
ELSE. AND THE BULK OF THE PRECIP WILL FALL THU NIGHT.  

THAT FRONT CROSSES ALL BUT FAR ERN CWA ZONES DURING FRI
MORNING...WITH CLEARING EXPECTED BEHIND IT IN THE AFTERNOON AS NW
FLOW PICKS UP. SHOULD BE ANOTHER WARM DAY...THOUGH AS DOWNSLOPING
TAKES HOLD AND COLD SURGE HAS TO WAIT FOR SECONDARY BOUNDARY LATE
FRI OR FRI EVENING.

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
WITH OCCLUSION CLEAR OF THE CWA BY EVE...WILL JUST SEE LEFTOVER
UPSLOPE SHSN IN THE MTNS IN NW FLOW. TRUE PUSH OF COLDER AIR WILL
ARRIVE EARLY SAT...WITH A BRIEF INCREASE IN SHSN ACTIVITY IN THE
HIGH TERRAIN. THIS WILL GIVE WAY TO VERY BRIEF S/WV RIDGING ACROSS
THE AREA LATE SAT BEFORE THINGS GET A LITTLE MORE INTERESTING.

VERY COMPLEX FCST BEYOND THE EARLY PART OF THE EXTENDED. THE MAIN
REASON FOR THE UNCERTAINTY IS BECAUSE THE PLAYERS ARE JUST
BEGINNING TO TAKE THE FIELD. WHAT WE DO KNOW IS THAT A VERY
CHAOTIC UPR LVL PATTERN WILL EVOLVE...WITH MULTIPLES S/WV TROFS TO
AFFECT THE SENSIBLE WX FOR NRN NEW ENGLAND LATE IN THE WEEKEND.
WHAT WE DO NOT KNOW IS EXACTLY HOW THESE S/WV FEATURES WILL
INTERACT WITH ONE ANOTHER.

FOR THE LAST DAY OR SO THE MODEL GUIDANCE HAS BEEN SEPARATED INTO
TWO CAMPS. THE GFS WITH SN REACHING AT LEAST THE SRN CWA...AND THE
REST OF THE GUIDANCE WITH A MORE SUPPRESSED...SRN LOW PRES.
ATTM...NRN STREAM S/WV TROFS ARE JUST REACHING THE W COAST OF
NOAM. ONE IS FCST TO SLIDE UNDERNEATH THE WRN CANADA RIDGING...AND
DIVE THRU THE INTER MTN WEST. THE OTHER IS FCST TO RIDE THE RIDGE
AND DIVE THRU THE CANADIAN PRAIRIES. THIS WILL BE TAKING PLACE
WHILE THE SRN STREAM S/WV ROUNDS THE BASE OF THE LARGE SCALE TROF
IN THE SWRN U.S. 

MODEL GUIDANCE AGREES THAT THE SRN STREAM AND INTER MTN S/WV
TROFS WILL INTERACT AND SUPPORT CYCLOGENESIS ACROSS THE GULF
COAST. THIS LOW PRES WILL TRACK TOWARDS THE MID ATLANTIC LATE
SAT/EARLY SUN. THE MODEL DIFFERENCES ARISE FROM THE AMOUNT OF NRN
STREAM INTERACTION FROM THE CANADIAN PRAIRIE S/WV. THE GFS HAS BEEN
FAVORING PHASING OF ALL THREE S/WV TROFS...RESULTING IN A
SIGNIFICANT COASTAL LOW PRES. CONVERSELY THE ECMWF...AND MOST
OTHER GUIDANCE...KEEPS THE NRN AND SRN STREAMS LARGELY UNPHASED.
THIS CREATES TOO MUCH CONFLUENCE OVER NEW ENGLAND...AND FORCES THE
LOW PRES OUT TO SEA. THE HANDLING OF THESE THREE UPR LVL FEATURES
WILL CHANGE OVER THE COMING MODEL CYCLES...AS THEY BECOME
INCREASINGLY MORE SAMPLED BY THE UPR AIR NETWORK. IN FACT 00Z
INITIALIZATION BY BOTH THE GFS AND ECMWF OF THE NRN STREAM WERE
VERY SIMILAR...SHOWING HOW MUCH CAN CHANGE AS THEY TRAVEL THRU THE
FLOW. SUBTLE CHANGES IN STRENGTH OR SPEED OF THESE WAVES WILL HAVE
LARGE DIFFERENCES ON THE EVENTUAL TRACK AND STRENGTH OF THIS LOW
PRES. WILL MAINTAIN A COMPROMISE OF THE TWO...LEANING MORE TOWARDS
THE ECMWF AS THE GFS REPRESENTS AN UPR BOUND AND UNLIKELY FULL
PHASE SCENARIO.

NEXT CHC AT PCPN WILL BE MIDWEEK...BUT WITH SO MUCH UNCERTAINTY
FOR THE WEEKEND HAVE NOT DEVIATED TOO FAR FROM PREVIOUS FCST.

.AVIATION /11Z THURSDAY THROUGH MONDAY/...
SHORT TERM...KLEB/KHIE WILL HANG ON TO MVFR CIGS UNTIL AFTER
SUNRISE AND SHOULD IMPROVE FOR MOST OF THE DAYLIGHT HOURS.
EVERYWHERE ELSE LOOKS GOOD FOR VFR THROUGH SUNSET TODAY. EXPECT TO
SEE IFR CONDS AT ALL TERMINALS FOR A GOOD CHUNK OF THE
OVERNIGHT...PERHAPS LINGERING INTO FRI MORNING...WITH A RETURN TO
VFR FRI AFTERNOON. 

LONG TERM...MVFR CONDS TO LINGER INTO SAT...WITH SHSN PSBL FOR
KHIE AND KELB. SUN FCST IS VERY UNCERTAIN...THOUGH SHSN LOOK PSBL
AT ALL TERMINALS. IF SNOWIER GFS SOLN PLAYS OUT...SCT IFR CONDS
COULD WORK INTO SRN NH DURING THE DAY.

.MARINE...
SHORT TERM...QUIET ON THE WATERS WITH WINDS AND SEAS EXPECTED TO
REMAIN BELOW SMALL CRAFT THRESHOLD THROUGH FRIDAY AFTERNOON.

LONG TERM...SCA CONDS PBSL BEHIND FNT ON FRI NGT INTO SAT.

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...NONE.
NH...NONE.
MARINE...NONE.