FXUS61 KOKX 150620
AFDOKX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
120 AM EST TUE DEC 15 2009
.SYNOPSIS...
A WEAK AREA OF LOW PRESSURE OVER THE GREAT LAKES WILL BYPASS THE
AREA TO THE NORTH ON TUESDAY...DRAGGING A COLD FRONT THROUGH THE
NORTHEAST IN THE MORNING. FOR THE MOST PART...THE FRONTAL PASSAGE
IS FORECAST TO BE DRY...BUT THERE MAY BE A BRIEF PERIOD OF LIGHT
PRECIPITATION. MUCH COLDER AIR WILL MOVE INTO THE AREA TUESDAY
NIGHT THROUGH THURSDAY ON A STRONG NORTHWEST FLOW. POLAR HIGH
PRESSURE OVER THE CENTRAL U.S. WILL BUILD EASTWARD THROUGH THE END
OF THE WEEK.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
LARGE SCALE WARM ADVECTION AHEAD OF AN AMPLIFYING SHORT WAVE OVER
THE UPPER MIDWEST THIS EVENING...WILL ALLOW FOR HIGH CLOUDS TO
STREAM ACROSS THE AREA FROM THE WEST. THE ASSOCIATED SFC LOW OVER
THE GREAT LAKES WILL TRACK INTO UPSTATE NY BY DAYBREAK...WITH ITS
TRAILING COLD FRONT APPROACHING THE AREA. A STRENGTHENING SLY FLOW
OVERNIGHT WILL LEAD TO STRATUS AND POSSIBLY SOME DRIZZLE AND
FOG...GENERALLY THOUGH AFTER MIDNIGHT. TEMPS SHOULD DROP LITTLE
FROM THEIR CURRENT VALUES DUE TO AN INCREASE IN CLOUD COVER AND
SLY FLOW OF 5 TO 10 MPH.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/...
THE COLD FRONT PUSHES THROUGH DURING THE MORNING HOURS TUE...POSSIBLY
PRECEDED BY SOME LIGHT DRIZZLE THROUGH MID MORNING. A LACK OF UPPER
SUPPORT AND DEEP MOISTURE DOES NOT WARRANT MUCH MORE. TEMPS ARE
FORECAST TO BE ABOVE FREEZING..THUS NO WINTRY WEATHER IS ANTICIPATED
AT THIS TIME. COLD ADVECTION BEHIND THE FRONT AND SUBSIDENCE WILL
ALLOW FOR PARTIAL CLEARING BY AFT WITH A GRADUALLY STRENGTHENING
WEST WIND. THIS WILL BE THE WARMEST DAY OF THE UPCOMING WEEK WITH
HIGHS AROUND 50 IN MOST LOCATIONS.
A NEGATIVE NAO PATTERN WILL ALLOW FOR THE AMPLIFYING SHORT WAVE
TROF OVER EASTERN CANADA AND THE NE U.S. TO CLOSE OFF INTO UPPER
LOW...WHERE IT WILL BECOME NEARLY STATIONARY. THIS WILL ALLOW FOR
A STEADY STREAM OF POLAR AIR TO FILTER INTO THE AREA FROM TUE
NIGHT INTO THU WITH DAYTIME HIGHS NOT GETTING OUT OF THE 30S WED
AND THU. GUSTY NW WINDS WILL ALSO ACCOMPANY THE COLD AIR WITH WIND
GUST UP TO 30 MPH POSSIBLE LATE TUE NIGHT AND WED. OVERNIGHT LOWS
WILL BE IN THE TEENS WELL NORTH AND WEST OF NYC...TO THE 20S
ELSEWHERE.
POLAR HIGH PRESSURE OVER THE MID SECTION OF THE COUNTRY WILL BE
SLOW TO BUILD EAST THROUGH THE PERIOD. THUS...DRY...COLD WEATHER
IS FORECAST THROUGH THE END OF THE WEEK.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
THE LONG TERM PATTERN IS DEFINED BY CONTINUANCE OF THE NEGATIVE
NAO (NORTH ATLANTIC OSCILLATION). THUS...BELOW NORMAL TEMPS
THROUGH THE PERIOD. 500 HPA HEIGHTS FALL TO 1-2 SIGMA BELOW CLIMO
FROM SOUTHERN NEW ENGLAND ALL THE WAY SOUTH INTO CARIBBEAN BY LATE
MONDAY.
AT THE SURFACE...ENSEMBLE FORECAST SYSTEMS (GFS) SUGGESTING HIGH
PRESSURE LOCALLY AS GULF CYCLOGENESIS EJECTS ACROSS FLORIDA AND INTO
THE OPEN ATLANTIC ON FRIDAY. UNCERTAINTY RELIES AROUND EAST COAST
CYCLOGENESIS ON SUNDAY UPPER LEVEL CUT OFF RETROGRADES AND SHARPENS
EASTERN US TROUGH IN RESPONSE TO BACK BUILDING GREENLAND HIGH. GFS
ENSEMBLE SYSTEM INDICATES THAT THE LOW WILL PASS WELL EAST OF THE
REGION.
00Z ECMWF HAS A FAIRLY SIGNIFICANT NOR'EASTER PASSING CLOSE TO THE
40N/70W BENCHMARK SUNDAY EVENING WITH THE POTENTIAL OF SIGNIFICANT
SNOW. THIS SINGLE ECMWF RUN IS MUCH CLOSER TO THE COAST AND SLOWER
THAN THE GFS ENSEMBLE SYSTEM AND GFS OPERATIONAL PRODUCTS. IT'S ALSO
VERY DIFFERENT THAN PREVIOUS RUN.
12Z ECMWF NOW IN WITH NOT MUCH OF ANYTHING. SO THE UNCERTAINTY
REMAINS.
NOW FOR SOMETHING COMPLETELY DIFFERENT...THE 12Z CANADIAN GEM TAKES
THE SOUTHERN SYSTEM AND PULLS IT NORTH FOR SATURDAY WITH A 962 BOMB
IN THE GULF OF MAINE BY SUNDAY AM. DON'T THINK THIS IS LIKELY...BUT
IT MAKES FOR HIGHER UNCERTAINTY FOR THE WEEKEND.
BOTTOM LINE...WILL KEEP A LOW CHC -SN FOR LATE SATURDAY NIGHT INTO
SUNDAY NIGHT WITH HIGH UNCERTAINLY. TEMPS WILL BE BELOW MOST
GUIDANCE DUE TO THE ABNORMALLY COLD PATTERN.
&&
.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
MAINLY A LOW END MVFR STRATUS DECK EXPECTED OVERNIGHT. COULD HAVE
ISOLD IFR CIGS...BUT NOT CONFIDENT WITH FLOW TURNING MORE SW.
THINK BEST CHC OF THIS WOULD BE AT KISP/KBDR/KGON WITH THE FLOW
RIGHT OFF THE WATER. MVFR VSBYS DEVELOPING OUTSIDE OF NYC
TERMS...POSSIBLY DROPPING TO IFR MAINLY AT KHPN/KSWF WHERE WINDS
WILL BE LIGHTEST. COLD FROPA EXPECTED BETWEEN 15Z AND 18Z. VFR MAY
RETURN AS EARLY AS 16Z AT WESTERN TERMS.
OUTLOOK 06Z WED THROUGH SAT...
TUE NIGHT THROUGH THU...VFR WITH GUSTY NW WINDS.
FRI...VFR.
SAT...VFR EXPECTED BUT NEED TO KEEP AN EYE ON POTENTIAL CSTL
STORM.
&&
.MARINE...
A SLY SWELL CONTINUES TO RESULT IN SEAS RIGHT AROUND 5 FT FOR A
SHORT TIME ON THE OCEAN ZONES...BUT THIS SHOULD NOT POSE A THREAT
TO SMALL CRAFT. THUS...HAVE DISCONTINUED THE SCA FOR SEAS ON THE
OCEAN. SEAS ARE FORECAST TO DROP 2 TO 4 FT LATER TONIGHT.
A TIGHT PRESSURE GRADIENT IS EXPECTED TO DEVELOP TUE NIGHT INTO
WED FOLLOWING A COLD FRONTAL PASSAGE TUE MORNING. A DEEP MIXED
LAYER WITH THE COLD AIR OVER THE WARMER WATERS RAISES THE POTENTIAL
FOR A MARGINAL GALE TUE NIGHT INTO WED ACROSS THE EASTERN WATERS.
THUS...A GALE WATCH HAS BEEN HOISTED FOR THE EASTERN WATERS...WITH
A SCA FOR THE WESTERN WATERS. AT A MINIMUM...SCA CONDITIONS WILL
PERSIST INTO THU.
SCA WILL LIKELY BE NEEDED THU NIGHT INTO FRI AS A TIGHT PRES
GRADIENT REMAINS ACROSS THE AREA.
TRANQUIL FRIDAY INTO AT LEAST EARLY SATURDAY. DEPENDING ON TRACK AND
INTENSITY OF LOW PRESSURE ON SUNDAY TO THE EAST OF THE
REGION...GALES ARE POSSIBLE.
&&
.HYDROLOGY...
LITTLE TO NO PRECIP IS FORECAST THROUGH THE END OF THE WEEK.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...NONE.
NY...NONE.
NJ...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 6 PM EST
WEDNESDAY FOR ANZ335-338-345-355.
GALE WATCH FROM THIS EVENING THROUGH WEDNESDAY AFTERNOON FOR
ANZ330-340-350-353.
&&
$$
