Marine Weather and Tide Forecast for Raleigh, NC

NEAR TERM /TODAY AND TONIGHT/
As of 954 AM Monday...

A Flood Watch is in effect through Tuesday morning

The inherited forecasted is on track this morning. Thus far, showers (and a few isolated storms in the south) have had fairly limited rainfall rates. A band of enhanced reflectivity associated with a weak MCV is entering the southern Piedmont as of this update. This area does have relatively lower FFG, so some near-term concern may be the urban areas out this way. However, as we progress throughout today expect additional waves of heavier showers/storms to move through all of central NC. HRRR probabilities for exceeding FFG over various temporal periods (1,3,6 hr) are near zero for much of our area through tomorrow. However, we do expect locally higher amounts (HRRR LPMM field shows swaths of potential 3-4 inches through Tuesday morning). As such, the classic urban areas will favor flash flood potential today and tonight, especially where/if these higher totals are realized.

While SPC only has us outlined in general thunder, we can't fully rule out a quick spin up tornado today. We've seen some weak rotation in a few cells already this morning over the southern Coastal Plain. Effective SRH is forecast to rise into the 100 m2s2 range and model-derived hodographs do so some hints of low-level curvature potential. Coupled with low LCLs, this kind of setup traditionally has occasionally led to a quick spin-up tornado or funnel cloud report. Overall though, the tornado chances are quite low today.

The bulk of moderate to heavy rain should largely lift north into VA late tonight through sunrise Tuesday morning. However, scattered shower chances will remain possible everywhere given the proximity to the closed low and the residual highly anomalous PWAT (150 to 175 % of normal).

Previous discussion from 340 AM Monday...

A nearly stationary upper level low that has been churning over the mouth of the Mississippi this past weekend, will finally begin to move north towards the Tennessee Valley. Weak insitu CAD will hang on across much of the area, ahead of the attendant warm front and potential weak triple point low forecast to extend along the SC-NC state line by daybreak Tuesday.

Beneath increasing upper level diffluence, a plume of strong southerly moisture transport will spread across the area through early Tuesday. This anomalous moisture, combined with deep layer ascent, will spawn repeated rounds of showers and thunderstorms this morning through tonight. The slow progression of this system and potential for training convection raise concerns for isolated to widely scattered flash flooding, particularly by the afternoon and evening in areas that experience multiple rounds of heavy convective rainfall as BL dewpoints increase 65-70 and weak instability develops.

Rainfall amounts through tonight are expected to average between 1- 2" across central NC, with localized heavier amounts of 2-4" possible where storms train. Urban areas, poor-drainage roads, and small streams will be the most susceptible. Some river flooding is also possible, mainly along the Haw and Rocky Rivers.

Highs ranging from near 70 across the northern Piedmont to mid 70s across the coastal plain and eastern Sandhills. Lows in the lower to mid 60s.

SHORT TERM /TUESDAY AND TUESDAY NIGHT/
As of 420 AM Monday...

* Showers/storms likely

On the ern periphery of a mid/upr-level cyclone that will move slowly newd from the Mid-South to the OH Valley, a negatively-tilted shortwave perturbation, and associated pocket of minus 12-15C temperatures and 20-40 meter height falls at 500 mb, will pivot nwd across the Carolinas on Tue and Virginias Tue night. That shortwave perturbation will be preceded by a generally north to south-oriented band of deep convection and convectively-amplified mid-level vorticity, embedded within a plume of tropical moisture characterized by PWs of 1.5-1.75" and 150-175% of normal, over ern NC and near and just east of RAH's Coastal Plain, at the start of the period. That convective band and deep moist axis will translate generally nwd across the Middle Atlantic through 12Z Wed.

At the surface, a triple surface wave and moist sector will migrate nwd across the Carolinas Tue and w-cntl VA Tue night.

The aforementioned band of deep convection and main focus for flash flooding, ongoing in or near the Coastal Plain at the start of the period, will gradually edge newd and out of RAH's area by mid- morning. In its wake, partial clearing may result from ern SC nwd and into srn and cntl NC, as a mid-level dry slot briefly streams nwd across the region. Associated pockets of relatively maximized insolation and diabatic heating will probably contribute to warming into the upr 70s-lwr 80s over the Sandhills and parts of the Coastal Plain and ne Piedmont, with generally mid-upr 70s elsewhere. When combined with seasonably rich low-level moisture and cool temperatures aloft, moderate instability of 1000-2000 J/kg will result. That heating will erode any weak convective inhibition present in the morning, with low LCLs and LFCs that will all favor the redevelopment of numerous showers/storms through the day, particularly given background forcing for ascent accompanying the negatively-tilted shortwave perturbation. 15-25 kts of 0-1 km bulk shear and slightly backed surface flow ahead of the triple point/trough will yield clockwise-curved and somewhat elongated hodographs in the lowest 2-3 km, with associated effective helicity values up to 100-150 m2/s2. Associated low-level shear profiles, beneath modest sswly mid-level flow of 20-30 kts, will probably promote mostly weak low-level rotation in even shallow, cells (mini- supercells). A conditional risk of a weak spin-up cannot be ruled out where instability and low-level shear may locally maximize.

That convection may linger numerous in coverage especially across the ne Piedmont and nrn Coastal Plain Tue evening, but otherwise diminish in coverage and intensity overnight, with low temperatures mostly in the lwr-mid 60s.

LONG TERM /WEDNESDAY THROUGH SUNDAY/
As of 445 AM Monday...

* Lingering showers/storms Wed-Wed night, then mainly dry until late Fri

* Turning hot, with scattered, possibly strong-severe convection Fri- Sat

A mid-level cyclone over the OH Valley at the start of the period will become an open wave trough while weakening and lifting newd across the lwr Great Lakes and Middle Atlantic through Thu night.
Progressive shortwave ridging will migrate from the MS Valley to the Middle and South Atlantic through the same time, then offshore.
Meanwhile, yet another closed and cutoff low will develop across the nrn Plains and nrn MS Valley and drift slowly ewd across the Great Lakes and srn ON/QC through the weekend.

At the surface, a trough will linger over the Middle Atlantic and Carolinas throughout the period, with a weak cold frontal passage in cntl NC possible late Sat into early Sun.

Above average probabilities of convection will linger with the slowly exiting mid/upr-level trough and cyclonic flow aloft mid- week, followed by a mainly dry Thu-into at least early Fri, beneath shortwave ridging and rising heights aloft. Convective chances will then increase late Fri, and especially Fri night, as falling heights and forcing for ascent, accompanying the cutoff low over the Great Lakes, glance the srn Middle Atlantic. A belt of seasonably strong, 35-45 kts of mid-level at its base and into parts of the srn Middle Atlantic would favor organized storms and risk of severe.

It will otherwise turn warmer, to hot particularly Fri, when forecast temperatures will be in the upr 80s to lwr 90s, and with heat index values in the upr 90s to near 100 mainly in the Sandhills and srn-cntl Coastal Plain.

AVIATION /11Z MONDAY THROUGH FRIDAY/
As of 700 AM Monday...

Through 12z Tuesday: Expect little to no improvement through the forecast period as widespread showers and scattered thunderstorms will continue to redevelop across the area through early Tuesday.
Restrictions should remain predominately IFR, with a brief period of MVFR at KFAY and KRWI through the evening, before potentially lowering to LIFR tonight/early Tuesday.

After 06Z Tuesday: Bands of moderate to heavy rain and IFR conditions will more-or-less continue through Tuesday morning.
Diurnally driven scattered showers and thunderstorms will continue Tuesday afternoon through late week. Early morning stratus and/or fog (IFR to LIFR) will be likely.

RAH WATCHES/WARNINGS/ADVISORIES
Flood Watch from late tonight through Tuesday morning for NCZ007>011-021>028-038>043-073>078-083>086-088-089.