textproduct: Gray - Portland

WHAT HAS CHANGED

No major changes were needed for this update other than to blend in the latest observations to the going forecast.

KEY MESSAGES

1. A front will bring chances for showers from the foothills northward today through tonight. Otherwise conditions remain mostly dry through Wednesday with above normal temperatures.

2. A slow moving cold front and waves of low pressure will bring chances for rain Thursday into the weekend.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION... Latest surface analysis places a west to east cold front across southern Quebec. Latest model guidance suggest this front will slowly sink south today through tonight and will provide a focus for clouds and showers. Skies will be mostly cloudy for much of the area, except for southern NH, while showers chances will be mostly confined to the foothills and points northward today. Across southern NH where there will more sun, temperatures will push into the low 70s with temperatures decreasing to the north and east.

Shower chances will expand southward early tonight before retreating northward going into Wednesday morning. The latest NBM generally keeps QPF below a tenth of an inch along and north of the mountains while 00Z CAMs suggest QPF could approach 0.25 to 0.5 inches along and north of the mountains.

The front will lift north of the area Wednesday leading to a mostly dry day. Skies will turn partly to mostly sunny along with temperatures at 850 mb climbing to +12C to +14C. This will push highs well into the 70s Wednesday with records in jeopardy at CON (75 in 1987)and PWM (74 in 1987). Above normal temperatures likely continue into Thursday ahead of a slow moving cold front discussed below.

KEY MESSAGE 2 DESCRIPTION...

A deep trough that brought flooding to parts of the Southwest is currently progressing into the PLains with models showing the trough closing off into an upper low. This upper low will weaken as it lifts northeast through the Great Lakes Thursday with an attendant cold front approaching from the west. All the while, another trough moving into California today will quickly cross the CONUS and short waves out of Canada may help spawn waves of low pressure along the cold front Friday into Saturday. While confidence is increasing that much of the area will see measurable rainfall late Thursday into Saturday, confidence is low on amounts with multiple moving parts needing to come together for an organized area of low pressure. Ensemble probabilities are around 60-70 percent for 0.5 inches during the Thursday to Saturday timeframe across much of the area. Ensembles do suggest there will be ample moisture available with PWATs running greater than 200 percent of normal Thursday through Saturday. While PoPs drop off Sunday, the pattern looks to remain unsettled into early next week with additional troughs swinging across the Northeast.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Through tonight: Ceilings begin lowering today but will likely remain VFR through the afternoon. Cigs likely lower to MVFR to possibly IFR from HIE to AUG to RKD and points north tonight. A passing shower will be possible at HIE today or tonight.

Outlook...

Wednesday: VFR conditions expected.

Thursday-Saturday: MVFR ceilings and rain are looking more likely in this timeframe, but exact timing is still uncertain.

MARINE

Winds generally stay below 25 kts and seas below 5 feet through Thursday. A slow moving cold front approach from the west late Thursday and a possible area of low pressure developing near coastal New England Friday into Saturday will bring potential for SCA conditions.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None.