textproduct: Raleigh

WHAT HAS CHANGED

As of 300 AM Tuesday...

* Cloudier and cooler (than the previous official forecast and the latest NBM one) today, with areas of fog especially in sern zones overnight

KEY MESSAGES

As of 300 AM Tuesday...

1) Cloudier and cooler (than the previous official forecast and the latest NBM one) today, with areas of fog especially in sern zones overnight

2) Much above normal temperatures and near record breaking warmth expected Thu through Mon, with rain chances returning Sun/Mon

DISCUSSION

As of 300 AM Tuesday...

KEY MESSAGE 1... Cloudier and cooler (than the previous official forecast and the latest NBM one) today, with areas of fog especially in sern zones overnight

The 00Z-observed GSO and RNK soundings sampled a pronounced frontal and cold air damming inversion, with associated 7-8C temperature differentials between inversion top and base, which should further saturate and yield lowering ceilings amid continued 925 mb-centered WAA and Fgen this morning. Areas of light rain or drizzle will also result from that frontal and isentropic ascent mainly across the far nrn Piedmont. Associated stability and ceilings will linger well into the day --probably all day over the Piedmont-- and with lifting and afternoon scattering most likely on the sern periphery of the damming regime and residual cool pool (ie. across the ern Carolinas and adjacent srn-cntl Coastal Plain and ern Sandhills in cntl NC). Temperatures today will consequently be much slower to rise and only attain highs probably in the lwr-mid 50s over the nrn Piedmont and nrn Coastal Plain, mid-upr 50s elsewhere in the Piedmont, and lwr- mid 60s over sern zones - or one to two categories on average (3-6F) cooler than the previous forecast and latest National Blend of Models.

Scattered to broken stratocumulus will probably linger over the Piedmont through the evening, while the aforementioned afternoon scattering/partial clearing in sern zones will favor stronger radiational cooling and development of areas of fog overnight-Wed morning.

KEY MESSAGE 2... Much above normal temperatures and near record breaking warmth expected Thu through Mon, with rain chances returning Sun/Mon

Confidence is high that strong mid level ridging will build over and just off the Southeast U.S coast through late this week through the weekend, as a deep closed southern stream low digs over and just W of NW Mexico. Surface high pressure will be situated roughly beneath this ridge, extending westward across the Southeast states, limiting the amount of low-level Atlantic- or Gulf-source moisture into central NC. This, in conjunction with dry/subsiding mid levels, favors minimal cloud cover, likely restricted to flat high-based daytime cu. Model consensus is that our daily low level thicknesses will be around 50 m above normal Thu and near 60 m above normal Fri- Mon, suggesting highs around 20 deg F above normal, given decent insolation, while daily lows will be similarly mild, in the mid 50s to lower 60s, close to the normal highs for this time of year, with Fri and Sat apt to be the warmest days. Both highs and lows will be very close to records at GSO/RDU/FAY.

Late in the weekend, passage of a northern stream shortwave trough through the St Lawrence Valley Sat night/Sun and additional waves close on its heels moving through Ontario/Quebec Sun night/Mon will serve to flatten the mid level ridge over the Carolinas. This will propel a surface cold front SE and S toward NC, although the front is expected to hold to our N through Mon. Nevertheless, a prefrontal increase in both clouds and PW should lead to increasing shower chances, mainly Sun through Mon. Despite the clouds and precip potential, thicknesses will remain anomalously high Sun/Mon, keep temps (especially lows) well above normal into early next week.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

As of 105 AM Tuesday...

Moist, nely flow at the surface, and gentle lift just above the surface, will favor a continued lowering of ceilings into LIFR-IFR range this morning, except low MVFR to IFR at FAY. Periods of light rain/drizzle and mist will also be possible, especially at INT and GSO, where the aforementioned lift will be maximized and ceilings will probably be lowest. Ceilings will only slowly lift into and through MVFR today, relatively quickest and with probable afternoon scattering to VFR at FAY and RWI. MVFR ceilings may meanwhile linger until late afternoon or early evening over the Piedmont. Scattering/ clearing will then favor radiational cooling of a residually cool surface layer that will have been sheltered (by the lingering clouds) from stronger daytime heating, such that areas of fog and low stratus will probably redevelop overnight-Wed morning, most likely at RWI and FAY.

Outlook: Stratus and/or fog will be favored at ern sites (ie. FAY and RWI) each morning through the rest of the week.

RAH WATCHES/WARNINGS/ADVISORIES

None.