THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


EXCESSIVE RAINFALL DISCUSSION


[Abbreviations and acronyms used in this product]
Geographic boundaries:    Map 1- [Color] [B/W Print Version]      Map 2 - [Color] [B/W Print Version]



EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 PM EDT WED OCT 22 2014

...VALID 18Z WED OCT 22 2014 - 00Z FRI OCT 24 2014...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NW CWSS 20 NW CXGM 35 SW CXGM 50 SE BHB 50 SE RKD 40 S RKD
50 E PSM 30 E BVY 15 ESE BOS BED 15 NW ASH CON 10 N DAW
20 SE IZG 30 WNW AUG 25 ESE GNR 25 NW CWSS.


...SOUTHWEST OREGON/NORTHWEST CALIFORNIA COASTAL RANGES AND THE
OREGON CASCADES...

LOCALIZED CONCERNS FOR RUNOFF ISSUES ARE GRADUALLY SHIFTING
FARTHER SOUTH...WITH THE FOCUS THIS PERIOD FOR THE COASTAL RANGES
OF SOUTHWEST OR AND NORTHWEST CA...INCLUDING THE OR CASCADES. A
DEEP PLUME OF MOISTURE AS NOTED IN THE LATEST GOES-SOUNDER PWAT
IMAGERY CONTINUES TO CROSS THE CENTRAL AND EASTERN PACIFIC OCEAN
AND IS AIMING INTO THE COASTAL RANGES IN CONJUNCTION WITH A
FRONTAL ZONE. OVER THE NEXT 24 HOURS...THIS FRONTAL ZONE WILL
SLOWLY SETTLE SOUTHEAST AND SHOULD ALLOW FOR THE DEEPER MOISTURE
TRANSPORT TO FOCUS GRADUALLY A BIT FARTHER SOUTH AND IMPACTING
AREAS AS FAR SOUTH AS THE NORTHWEST CA COASTAL RANGES BY LATER
TONIGHT AND EARLY THURSDAY. PERSISTENT AND STRONG
SOUTH-SOUTHWESTERLY FLOW OF 50 TO 55 KTS EMBEDDED WITHIN THE DEEP
MOISTURE PLUME AHEAD OF THE FRONT WILL FAVOR HEAVY RAINS AND
ESPECIALLY WITH STRONG OROGRAPHIC FORCING. THE LATEST MODELS
REMAIN IN GOOD AGREEMENT WITH THE SET-UP...AND CONFIDENCE IS
RATHER HIGH ON SEEING FAIRLY WIDESPREAD WIDESPREAD 2 TO 4 INCH
AMOUNTS...WITH ISOLATED HEAVIER AMOUNTS. CANNOT RULE OUT SOME
RUNOFF PROBLEMS...BUT ANY CONCERNS SHOULD BE LOCALIZED IF NOT
ISOLATED IN NATURE.


...NEW ENGLAND...

THE CLOSED LOW INITIALLY OVER THE MID ATLANTIC WILL BE SWINGING
SLOWLY NORTHEASTWARD OFF THE NORTHERN MID ATLANTIC COAST AND
TOWARD SOUTHERN NEW ENGLAND THIS PERIOD. PERSISTENT AND STRONG
ONSHORE EASTERLY FLOW TO THE NORTH AND EAST OF THIS MID TO UPPER
LEVEL CLOSED LOW WILL MAINTAIN WET CONDITIONS FROM THE COASTAL
MID-ATLANTIC NORTHWARD INTO NEW ENGLAND...WITH MUCH OF NEW ENGLAND
EXPECTED TO SEE A SIGNIFICANT EXPANSION OF MODERATE TO HEAVY
RAINFALL LATER TONIGHT AND THROUGH THURSDAY. THE 12Z GFS AND 00Z
ECMWF SUGGEST A DEEP ATLANTIC FETCH OF MOISTURE...WITH H85
MOISTURE TRANSPORT FORECAST TO REACH 3 TO 4 STD DEV ABOVE NORMAL
BY EARLY THURSDAY OVER MUCH NORTHERN NEW ENGLAND. ALL THE
WHILE...A ROBUST MID TO UPPER LEVEL DEFORMATION ZONE IS FORECAST
TO SET UP OVER THE REGION GIVEN PROXIMITY OF THE CLOSED LOW. THE
GLOBAL MODELS LED BY THE GFS AND ECMWF SUGGEST THE HEAVIEST
RAINFALL AMOUNTS FOCUSING OVER CENTRAL/EASTERN ME...WITH THE
HI-RES GUIDANCE...INCLUDING THE 12Z NAM-CONEST...12Z ARW AND 12Z
NMMB FAVORING SOMEWHAT HEAVIER TOTALS A LITTLE FARTHER SOUTH OVER
SOUTHERN ME AND INTO COASTAL AREAS OF EASTERN MA AND NH. WPC QPF
FAVORED A BLENDED APPROACH BETWEEN CAMPS AT THIS TIME GIVEN THE
TROUBLE THE LATEST GUIDANCE APPEARS TO BE HAVING IN HANDLING THE
QPF DETAILS OVER THE MID-ATLANTIC REGION. IN ANY CASE...HEAVY
RAINFALL AMOUNTS ARE EXPECTED...WITH WPC FAVORING 2 TO 4 INCH
RAINFALL AMOUNTS WITH ISOLATED HEAVIER TOTALS GIVEN SUCH A STRONG
LOW LEVEL JET FORECAST TO COME IN OFF THE ATLANTIC OCEAN. SOME
ISOLATED HEAVIER AMOUNTS CANNOT BE RULED OUT...AND THERE WILL BE
SOME CONCERN FOR SOME RUNOFF PROBLEMS AT LEAST LOCALLY.

ORRISON




Last Updated: 254 PM EDT WED OCT 22 2014