Marine Weather and Tide Forecast for Irmo, SC

NEAR TERM /THROUGH TONIGHT/
Key Message(s):

- Dry high pressure will build into the region through tonight

Satellite imagery shows some high clouds moving across the Southeast this morning. A cold front moving through North Carolina this morning will arrive in the area around sunrise, driven by a shortwave that will be moving off the Mid- Atlantic coast.

Behind this shortwave, winds will shift from west to north and dewpoints will fall into the single digits north to 20s south.
The low level jet this morning will produce a brief period of wind gusts from 10 to 15 mph, but taper by midday. Expect dry and cool with temperatures below normal. Highs will range from the middle 40s north to lower to middle 50s far south.

Expect a few high clouds tonight, but winds should remain rather light. This will allow temperatures to drop off nicely across the CWA Expect lows in the lower to middle 20s north/central to near 30 across the CSRA.

SHORT TERM /THURSDAY/
Key Message(s):

- Cool, dry weather continues. Breezy Thursday.

An upper level trough will dig into the eastern US on Thursday with high pressure pushing offshore on Friday. PWAT values from Thursday to 00Z on Friday will range from 0.2 to 0.4 inches indicating continued dry weather. Temperatures should be warmer on Thursday than the previous day as the air mass modifies.
Expect highs in the mid to upper 50s. A tight pressure gradient will allow for breezy winds on Thursday with gusts to 25 mph, subsiding overnight as high pressure moves over the area. Lows on Thursday night will range from mid 20s to around freezing. On Friday, the center of the surface high will shift offshore promoting increasing southerly flow across the Southeast through the day. Expect highs in the 50s. Moisture advection remains weak during the daylight hours so we expect rainfall to hold off until overnight.

LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
Key Message(s):

- Widespread rain Friday Night and Saturday, thunderstorms unlikely - Well below normal temperatures return for Sun night and next week - Moisture spreads into the Southeast near the end of the period

Rex blocking currently over the West Coast will break down over the course of this week. The cutoff low will eventually be picked up and move into the eastern US. At the surface, the associated low pressure system is expected to lift from the south central US into the southern Appalachians. Deep, southerly flow develops across the forecast area Friday night in response to the approaching system.
PWAT values rise from one third of an inch Friday evening to 1-1.3 inches by Saturday morning. Divergence aloft, convergence ahead of the front, and deep moisture all support widespread showers. Weak conditional instability limits the threat of thunderstorms. Rainfall will taper off late Saturday as the frontal system moves east of the area and dry, cold air takes its place.

An anomalously deep 500 mb trough (near the NAEFS climatological minimum for this time of year) will dip into the north central US late this weekend and early next week. A strong surface high will filter arctic air into the central and eastern US. There is very high confidence in temperatures well below normal. 90 percent of the NBM members have high temperatures in the 40s or lower for Monday through Wednesday. Mean temperatures have also been trending colder for early next week. There are a growing number of ensemble members showing precipitation over the Southeast from early to mid next week. 50 to 70 percent of ECMWF members and 30 to 50 percent of GEFS members record measurable precipitation. The synoptic setup of abnormally cold air over the region and potential for moisture to spread into the forecast area is a situation that will continue to need monitoring. That said there is still a large spread in the timing of any potential precip and amounts, or lack thereof. This ultimately is keeping PoPs limited to slight chance for the end of the long term since the confidence of precip at any given period is low. Model guidance varies greatly in the track of a low pressure system which may bring the Southeast some form of wintry precip near the end of the long term.

AVIATION /09Z WEDNESDAY THROUGH SUNDAY/
VFR Conditions Continue....

Satellite this morning continues to show some high thin clouds moving across the region. Surface observations across Georgia and the Carolinas indicate ceilings are between 15K and 25K feet and guidance suggests that FEW to SCT skies will continue through much of the period. West winds from 4 to 8 knots early this morning will shift to a northerly direction behind a cold front between 12Z and 14Z this morning along with a slight increase in wind speeds through midday. Winds will once again slacken this evening and tonight with near calm winds at most TAF sites.

EXTENDED AVIATION OUTLOOK...The next chance for significant restrictions will be late Friday and Saturday as moisture spreads into the Southeast.

CAE WATCHES/WARNINGS/ADVISORIES
SC...None.
GA...None.