Now that the heavy rain is long gone, time to focus on the surge of polar/modified arctic air that will drop south this weekend. There will also be an interesting little storm system next Tue.-Wed.
The cold air will start to seep into the First Coast Thu. night-Fri. with lows by early Fri. in the mid to upper 30s & highs Fri. in the low 60s. The coldest air arrives over the weekend. It'll be breezy so expect low wind chills as highs Sat. only reach the mid 50s to around 60 with lows Sat. night/early Sun. near 30 inland, close to 32 along I-95 & in the mid to upper 30s closer to the coast. There should be enough wind & cloudiness to save the area from even colder temps. But winds will be lighter Sun. night with fewer clouds which should allow for the coldest temps. from this chilly period as lows bottom out in the mid to upper 20s inland...upper 20s to low 30s along I-95 to the mid 30s at the beaches. While not as cold, temps. will still dip to near freezing inland early Tue. for another night of frost.
Records are pretty low, so we'll likely not reach record cold.
Sun., March 3: 23/1980
Mon., March 4: 24/1980
Tue., March 5: 28/1971
As for precip.....it'll generally be dry as the there will be very limited moisture in this pattern. But a strong upper level disturbance Sat. afternoon through early Sun. might be able to trigger a few widely scattered brief showers but not likely measurable. Now -- & I write about this with great hesitation so as not to incite great anxiety(!) -- we have to look at the temp. profile of the atmosphere to see if we could get any frozen precip. The short answer is "yes" BUT very, very light if at all & most likely ice pellets (sleet). Even though temps. will be well above freezing when precip. occurs, the air aloft will be very cold & could support some very light sleet. There's no threat for accumulation, & you would have to be standing out in the precip. to even know it's occurring. In any case....it won't be any big deal & the real story for the weekend will be the very cold temps.
Then a strong upper level disturbance will dive into the Southeast U.S. by Tue. which will develop low pressure north of Jax & should bring some rain showers late Tue. night/Wed. followed by yet another -- but shorter/not as intense -- shot of cold air. The diagram below shows how sleet forms -- snow melting through a warm layer then refreezing. In our case for late Sat./Sat. night, the surface temps. will be well above freezing (vs. what you see in the diageram below).
The recent heavy rain has greatly lowered the wildfire danger for the time being. Effective March 1st, there will be new criteria for fire danger forecasts. From our Jax N.W.S. & the Fl. Forest Service:
CRITERIA FOR FIRE WEATHER HEADLINES FOR NORTHEASTFLORIDA IS DUE TO CHANGE ON FRIDAY...MARCH 1ST.
THE NEW CRITERIA FOR RED FLAG WARNINGS AND FIRE WEATHER WATCHES WILL BE:
FOUR CONSECUTIVE HOURS OF FORECAST RELATIVE HUMIDITY OF 28 PERCENT OR LESS AND FORECAST ENERGY RELEASE COMPONENT (ERC) VALUES OF 37 OR GREATER...OR...
FORECAST RELATIVE HUMIDITY VALUE OF 28 PERCENT OR LESS AND FORECAST 20 FOOT SUSTAINED WINDS OF 15 MPH OR GREATER...ALONG WITH AN ERC VALUE OF 26 OR GREATER.
DISPERSION INDICES GREATER THAN 75 WILL NO LONGER TRIGGER A RED FLAG WARNING OR FIRE WEATHER WATCH.
Speaking of heavy rain....check out the map below (Advanced Hydrologic Predicition Service) which shows doppler estimated rainfall for the past week -- impressive over SE Ga. & far North Fl.
The map below shows rainfall for the First Coast from Sun.-Tue. but does NOT include the heavy rain over SE Ga. & moderate rain over NE Fl. Sat.
A beautiful "mackerel" sky (named for the resemblance to scales on a fish) Wed. afternoon as seen below from our Landing Skycam.
